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Abstract
Although the last two decades have seen a substantial decline in malaria incidence and mortality due to the use of insecticide-treated bed nets and artemisinin combination therapy, the threat of drug resistance is a constant obstacle to sustainable malaria control. Given that patients can die quickly from this disease, public health officials and doctors need to understand whether drug resistance exists in the parasite population, as well as how prevalent it is so they can make informed decisions about treatment. As testing for drug efficacy before providing treatment to malaria patients is impractical, researchers need molecular markers of resistance that can be more readily tracked in parasite populations. To this end, much work has been done to unravel the genetic underpinnings of drug resistance in Plasmodium falciparum. The aim of this review is to provide a broad overview of common genomic approaches that have been used to discover the alleles that drive drug response phenotypes in the most lethal human malaria parasite.
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Affiliation(s)
- Frances Rocamora
- Department of Pediatrics, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
| | - Elizabeth A Winzeler
- Department of Pediatrics, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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Prevalence of Anemia and Its Associate Factors among Women of Reproductive Age in Lao PDR: Evidence from a Nationally Representative Survey. Anemia 2021; 2021:8823030. [PMID: 33520310 PMCID: PMC7822650 DOI: 10.1155/2021/8823030] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 12/24/2020] [Accepted: 12/30/2020] [Indexed: 11/18/2022] Open
Abstract
Introduction Anemia continues to be a major public health problem significant among women of reproductive age (WRA) in developing countries, including Lao People's Democratic Republic (Lao PDR), where the prevalence of anemia among women remains high. This study aimed to assess the prevalence of anemia and its associated factors among WRA 15–49 years in Lao PDR. Methods We conducted a cross-sectional study, using the Lao Social Indicator Survey II, 2017 dataset. A total of 12,519 WRA tested for anemia were included in this study, through multistage sampling approaches. Binary logistic regression was used to determine the associated factors of anemia. Results Of 12,519 women, 4,907 (39.2%) were anemic. Multivariate logistic regression revealed that living in central provinces (aOR: 2.16, 95% CI: 1.96–2.38), rural area (aOR: 1.1, 95% CI: 1.00–1.20), large family size with more than 6 persons (aOR: 1.14, 95% CI: 1.01–1.29), pregnancy (aOR: 1.46, 95% CI: 1.22–1.74), having any adverse pregnancy outcomes (aOR: 1.14, 95% CI: 1.03–1.25), poor drinking water (aOR: 1.24, 95% CI: 1.10–1.39), and poor sanitation facility (aOR: 1.15, 95% CI: 1.03–1.28) were significantly associated with an increased risk of anemia. Conversely, four factors were associated with anemia preventively, including being aged 25–34 years (aOR: 0.81, 95% CI: 0.74–0.90), postsecondary education (aOR: 0.76, 95% CI: 0.60–0.97), Hmong-Mien ethnicity (aOR: 0.48, 95% CI: 0.39–0.59), and watching television almost daily (aOR: 0.84, 95% CI: 0.75–0.95). Conclusion Anemia continues to be a major public health challenge in Lao PDR. Interventions should be considered on geographic variations, improving safe water and sanitation facility, promoting of iron supplements during pregnancy, and health education through mass media for women in rural areas.
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Cowell AN, Winzeler EA. The genomic architecture of antimalarial drug resistance. Brief Funct Genomics 2019; 18:314-328. [PMID: 31119263 PMCID: PMC6859814 DOI: 10.1093/bfgp/elz008] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 03/19/2019] [Accepted: 04/09/2019] [Indexed: 11/15/2022] Open
Abstract
Plasmodium falciparum and Plasmodium vivax, the two protozoan parasite species that cause the majority of cases of human malaria, have developed resistance to nearly all known antimalarials. The ability of malaria parasites to develop resistance is primarily due to the high numbers of parasites in the infected person's bloodstream during the asexual blood stage of infection in conjunction with the mutability of their genomes. Identifying the genetic mutations that mediate antimalarial resistance has deepened our understanding of how the parasites evade our treatments and reveals molecular markers that can be used to track the emergence of resistance in clinical samples. In this review, we examine known genetic mutations that lead to resistance to the major classes of antimalarial medications: the 4-aminoquinolines (chloroquine, amodiaquine and piperaquine), antifolate drugs, aryl amino-alcohols (quinine, lumefantrine and mefloquine), artemisinin compounds, antibiotics (clindamycin and doxycycline) and a napthoquinone (atovaquone). We discuss how the evolution of antimalarial resistance informs strategies to design the next generation of antimalarial therapies.
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Affiliation(s)
- Annie N Cowell
- Division of Infectious Diseases and Global Health, Department of Medicine, University of California, San Diego, Gilman Dr., La Jolla, CA, USA
| | - Elizabeth A Winzeler
- Division of Host-Microbe Systems & Therapeutics, Department of Pediatrics, University of California, San Diego, Gilman Dr., La Jolla, CA, USA
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Vilay P, Nonaka D, Senamonty P, Lao M, Iwagami M, Kobayashi J, Hernandez PM, Phrasisombath K, Kounnavong S, Hongvanthong B, Brey PT, Kano S. Malaria prevalence, knowledge, perception, preventive and treatment behavior among military in Champasak and Attapeu provinces, Lao PDR: a mixed methods study. Trop Med Health 2019; 47:11. [PMID: 30700970 PMCID: PMC6347756 DOI: 10.1186/s41182-019-0138-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/14/2019] [Indexed: 11/10/2022] Open
Abstract
Background Malaria is a major health problem in Lao People's Democratic Republic (Lao PDR) with high transmission in remote and forest areas, particularly in the South. The military is at risk of malaria infection especially those deployed in forest areas. This study determined the prevalence of malaria infection and assessed knowledge, perception, and preventive and treatment behavior regarding malaria among military personnel in two southern provinces in Lao PDR. Methods Quantitative and qualitative approaches were undertaken in Champasak and Attapeu provinces in 2017. From 313 military personnel, quantitative data were collected through questionnaire-based interviews and blood samples used for parasite detection by polymerase chain reaction (PCR). Qualitative data were collected through 7 focus group discussions and 17 in-depth interviews among 49 military personnel. Fisher's exact test and Mann-Whitney U test were used to assess the association between malaria infection and participant characteristics. Content analysis for qualitative data was performed to explore perception and treatment behaviors regarding malaria. Results The prevalence of malaria infection was 11.2% (Plasmodium falciparum: 1.3%, Plasmodium vivax: 9.3% and mixed infections: 0.6%). Many participants understood that malaria is transmitted through mosquito bites, although they did not necessarily know the name of vector mosquitoes (Anopheles). Surprisingly, more than a half also believed that malaria is transmitted through drinking stream water. One-third of the participants used long-lasting insecticidal nets. Due to limited supply, participants were often unable to use mosquito repellent and coils when necessary. Because participants were unable to receive timely diagnosis and appropriate treatment for malaria in their camps, they commonly practiced self-treatment using antibiotics, painkillers, and/or traditional medicines. They only go to a healthcare facility through their supervisor if their conditions worsen. Conclusions The prevalence of symptomatic and asymptomatic malaria was conspicuous among military in forest areas. Many participants believed that malaria is transmitted not only by mosquito bites but also from drinking stream water. Preventive equipment was often insufficient. Self-treatment was practiced before referring to healthcare facility. To further prevent military from contracting malaria, the National Malaria Control Program and military body should provide adequate and suitable health education, protective equipment, and on-site malaria case management.
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Affiliation(s)
- Phoutnalong Vilay
- 1Department of Global Health, Graduate School of Health Sciences, University of the Ryukyus, 207 Uehara-cho, Okinawa, 903-0215 Japan.,2Center of Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR.,SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR
| | - Daisuke Nonaka
- 1Department of Global Health, Graduate School of Health Sciences, University of the Ryukyus, 207 Uehara-cho, Okinawa, 903-0215 Japan.,SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR
| | - Phosadeth Senamonty
- Military Institute of Diseases Prevention, Department of Military Medical, Ministry of Defense, Vientiane, Lao PDR
| | - Malayvanh Lao
- Military Institute of Diseases Prevention, Department of Military Medical, Ministry of Defense, Vientiane, Lao PDR
| | - Moritoshi Iwagami
- SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR.,5Department of Tropical Medicine and Malaria, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo, 162-8655 Japan.,6Institut Pasteur du Laos, Ministry of Health, Vientiane, Lao PDR
| | - Jun Kobayashi
- 1Department of Global Health, Graduate School of Health Sciences, University of the Ryukyus, 207 Uehara-cho, Okinawa, 903-0215 Japan.,SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR
| | - Paul Michael Hernandez
- 1Department of Global Health, Graduate School of Health Sciences, University of the Ryukyus, 207 Uehara-cho, Okinawa, 903-0215 Japan.,7Department of Environmental and Occupational Health, College of Public Health, University of the Philippines Manila, 625 Pedro Gil Street, Ermita, 1000 Manila, Philippines
| | | | - Sengchanh Kounnavong
- SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR.,9Lao Tropical and Public Health Institute, Ministry of Health, Vientiane, Lao PDR
| | - Bouasy Hongvanthong
- 2Center of Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR.,SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR
| | - Paul T Brey
- SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR.,6Institut Pasteur du Laos, Ministry of Health, Vientiane, Lao PDR
| | - Shigeyuki Kano
- SATREPS Project for Parasitic Diseases, Vientiane, Lao PDR.,5Department of Tropical Medicine and Malaria, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo, 162-8655 Japan
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Labbé AC, Pillai DR, Hongvangthong B, Vanisaveth V, Pomphida S, Inkathone S, Hay Burgess DC, Kain KC. The performance and utility of rapid diagnostic assays forPlasmodium falciparummalaria in a field setting in the Lao People's Democratic Republic. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2016. [DOI: 10.1080/00034983.2001.11813684] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Labbé AC, Bualombai P, Pillai DR, Zhong KJY, Vanisaveth V, Hongvanthong B, Looareesuwan S, Kain KC. Molecular markers for chloroquine-resistantPlasmodium falciparummalaria in Thailand and Laos. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2016. [DOI: 10.1080/00034983.2001.11813697] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Omar SA, Adagu IS, Gump DW, Ndaru NP, Warhurst DC. Plasmodium falciparumin Kenya: high prevalence of drug-resistance-associated polymorphisms in hospital admissions with severe malaria in an epidemic area. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2016. [DOI: 10.1080/00034983.2001.11813683] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Golassa L, Kamugisha E, Ishengoma DS, Baraka V, Shayo A, Baliraine FN, Enweji N, Erko B, Aseffa A, Choy A, Swedberg G. Identification of large variation in pfcrt, pfmdr-1 and pfubp-1 markers in Plasmodium falciparum isolates from Ethiopia and Tanzania. Malar J 2015; 14:264. [PMID: 26152336 PMCID: PMC4495614 DOI: 10.1186/s12936-015-0783-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 06/27/2015] [Indexed: 01/15/2023] Open
Abstract
Background Plasmodium falciparum resistance to anti-malarials is a major drawback in effective malaria control and elimination globally. Artemisinin-combination therapy (ACT) is currently the key first-line treatment for uncomplicated falciparum malaria. Plasmodium falciparum genetic signatures at pfmdr-1, pfcrt, and pfubp-1 loci are known to modulate in vivo and in vitro parasite response to ACT. The objective of this study was to assess the distribution of these resistance gene markers in isolates collected from different malaria transmission intensity in Ethiopia and Tanzania. Methods Plasmodium falciparum clinical isolates were collected from different regions of Ethiopia and Tanzania. Genetic polymorphisms in the genes pfcrt, pfmdr-1 and pfubp-1 were analysed by PCR and sequencing. Frequencies of the different alleles in the three genes were compared within and between regions, and between the two countries. Results The majority of the isolates from Ethiopia were mutant for the pfcrt 76 and wild-type for pfmdr-1 86. In contrast, the majority of the Tanzanian samples were wild-type for both pfcrt and pfmdr-1 loci. Analysis of a variable linker region in pfmdr-1 showed substantial variation in isolates from Tanzania as compared to Ethiopian isolates that had minimal variation. Direct sequencing of the pfubp-1 region showed that 92.8% (26/28) of the Ethiopian isolates had identical genome sequence with the wild type reference P. falciparum strain 3D7. Of 42 isolates from Tanzania, only 13 (30.9%) had identical genome sequences with 3D7. In the Tanzanian samples, 10 variant haplotypes were identified. Conclusion The majority of Ethiopian isolates carried the main marker for chloroquine (CQ) resistance, while the majority of the samples from Tanzania carried markers for CQ susceptibility. Polymorphic genes showed substantially more variation in Tanzanian isolates. The low variability in the polymorphic region of pfmdr-1 in Ethiopia may be a consequence of low transmission intensity as compared to high transmission intensity and large variations in Tanzania.
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Affiliation(s)
- Lemu Golassa
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia. .,Armauer Hansen Research Institute, Addis Ababa, Ethiopia.
| | - Erasmus Kamugisha
- Department of Biochemistry, Catholic University of Health and Allied Sciences-Bugando, Mwanza, Tanzania.
| | | | - Vito Baraka
- National Institute for Medical Research, Tanga, Tanzania. .,International Health Unit, Department of Epidemiology, University of Antwerp, Antwerp, Belgium.
| | - Alex Shayo
- The Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania.
| | | | - Nizar Enweji
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
| | - Berhanu Erko
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia.
| | - Abraham Aseffa
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia.
| | - Angel Choy
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
| | - Göte Swedberg
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
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Hawkes M, Conroy AL, Opoka RO, Namasopo S, Liles WC, John CC, Kain KC. Use of a three-band HRP2/pLDH combination rapid diagnostic test increases diagnostic specificity for falciparum malaria in Ugandan children. Malar J 2014; 13:43. [PMID: 24484540 PMCID: PMC3922073 DOI: 10.1186/1475-2875-13-43] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 01/27/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rapid diagnostic tests (RDTs) for malaria provide a practical alternative to light microscopy for malaria diagnosis in resource-limited settings. Three-band RDTs incorporating two parasite antigens may have enhanced diagnostic specificity, relative to two-band RDTs with a single parasite antigen (typically histidine-rich protein 2 [HRP2]). METHODS Phase 1: 2,000 children, two months to five years of age, admitted to a referral hospital in Jinja, Uganda, with acute febrile illness were enrolled. A WHO highly rated three-band RDT was compared to light microscopy of thick peripheral blood films read by local expert microscopists.Phase 2: the three-band RDT was used as a screening tool for inclusion of patients in a clinical trial, and subjects with three positive RDT bands were tested by microscopy using blood samples drawn in parallel. Discordant results were adjudicated by PCR. RESULTS Phase 1: 1,648 children had both a RDT and peripheral blood smear performed. The specificity of a RDT with all three bands positive was 82% (95% CI: 79-85%) compared to 62% (95% CI: 59-66%) for HRP2 alone. The sensitivity was 88% (95% CI: 85-89%) and 94% (95% CI: 92-95%) for three-band positive RDT and HRP2 antigen, respectively. 119 patients (7.2%) had a positive HRP2 band, but negative parasite lactate dehydrogenase (pLHD) band and negative peripheral smear, and 72 (61%) of these had received pre-treatment with anti-malarials, suggesting a false positive HRP2 result (p = 0.002).Phase 2: the positive predictive value (PPV) of the three-band RDT was 94% (95% CI 89%-97%) using microscopy as the reference standard. However, microscopy-discordant results were shown to be positive for P. falciparum by PCR in all cases, suggesting that the PPV was in fact higher. CONCLUSION The pLDH antigen on three-band RDTs, used in combination with HRP2, provides added diagnostic specificity for malaria parasitaemia and may be useful to distinguish acute infection from recently treated infection. In situations where diagnostic specificity is desirable (e.g., for selection of malaria-infected participants in clinical trials), a three-band RDT should be considered in a sub-Saharan African setting.
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Affiliation(s)
| | | | | | | | | | | | - Kevin C Kain
- Department of Medicine, University of Toronto, Toronto, Canada.
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Khalil IF, Alifrangis M, Tarimo DS, Staalsø T, Satti GMH, Theander TG, Rønn AM, Bygbjerg IC. The roles of thepfcrt 76Tandpfmdr1 86Ymutations, immunity and the initial level of parasitaemia, in predicting the outcome of chloroquine treatment in two areas with different transmission intensities. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2013; 99:441-8. [PMID: 16004703 DOI: 10.1179/136485905x46441] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The resistance of Plasmodium falciparum to chloroquine (CQ) is probably mediated by point mutations in two genes: pfcrt and pfmdr1. The aim of the present study was to investigate, in patients treated with CQ, the association between host factors, such as immunity and initial level of parasitaemia, and the ability to clear P. falciparum parasites carrying the key chloroquine-resistance (CQR) mutations, pfcrt 76T and pfmdr1 86Y. Identical CQ-efficacy trials were performed in 51 young children (aged <5 years) from Kibaha, in north-western Tanzania, and 44 patients (aged 3-57 years) from Darawish, in eastern Sudan. In both areas, all the CQ-treatment failures had infections with the 76T and 86Y alleles before treatment. Although the presence of these two alleles was significantly associated with treatment failure in Sudan (P=0.001), the corresponding association in Tanzania did not reach statistical significance (P=0.1). Of the 39 patients from Darawish and 44 from Kibaha who harboured parasites with the CQR mutations, 12 and 19, respectively, managed to clear their parasitaemias. The ability to clear CQR parasites was significantly associated with the initial level of parasitaemia (with P-values of 0.05 in Tanzania and 0.01 in Sudan) and with age-- the best surrogate for protective immunity in endemic areas (with P-values of 0.02 in Tanzania and 0.001 in Sudan). These results confirm previous observations that indicated that the 76T and 86Y alleles play a role in the mechanism of CQR, although other factors, such as level of parasitaemia when treated and age, are also important. The 76T and 86Y alleles could still be used as predictive markers for CQR, in non-immune individuals and low-transmission areas.
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Affiliation(s)
- I F Khalil
- Department of International Health, Institute for Medical Microbiology and Immunology and Center for Medical Parasitology (CMP), Copenhagen, Denmark.
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Adhin MR, Labadie-Bracho M, Bretas G. Molecular surveillance as monitoring tool for drug-resistant Plasmodium falciparum in Suriname. Am J Trop Med Hyg 2013; 89:311-6. [PMID: 23836573 DOI: 10.4269/ajtmh.12-0695] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The aim of this translational study was to show the use of molecular surveillance for polymorphisms and copy number as a monitoring tool to track the emergence and dynamics of Plasmodium falciparum drug resistance. A molecular baseline for Suriname was established in 2005, with P. falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance (pfmdr1) markers and copy number in 40 samples. The baseline results revealed the existence of a uniformly distributed mutated genotype corresponding with the fully mefloquine-sensitive 7G8-like genotype (Y184F, S1034C, N1042D, and D1246Y) and a fixed pfmdr1 N86 haplotype. All samples harbored the pivotal pfcrtK76T mutation, showing that chloroquine reintroduction should not yet be contemplated in Suriname. After 5 years, 40 samples were assessed to trace temporal changes in the status of pfmdr1 polymorphisms and copy number and showed minor genetic alterations in the pfmdr1 gene and no significant changes in copy number, thus providing scientific support for prolongation of the current drug policy in Suriname.
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Affiliation(s)
- Malti R Adhin
- Department of Biochemistry, Faculty of Medical Sciences, Anton de Kom Universiteit van Suriname, Paramaribo, Suriname.
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Mayxay M, Khanthavong M, Chanthongthip O, Imwong M, Pongvongsa T, Hongvanthong B, Phompida S, Vanisaveth V, White NJ, Newton PN. Efficacy of artemether-lumefantrine, the nationally-recommended artemisinin combination for the treatment of uncomplicated falciparum malaria, in southern Laos. Malar J 2012; 11:184. [PMID: 22681769 PMCID: PMC3523969 DOI: 10.1186/1475-2875-11-184] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Accepted: 05/24/2012] [Indexed: 11/13/2022] Open
Abstract
Background The Lao Government changed the national policy for uncomplicated Plasmodium falciparum malaria from chloroquine to artemether-lumefantrine (AL) in 2005. Since then, no information on AL efficacy has been reported. With evidence of resistance to artemisinin derivatives in adjacent Cambodia, there has been a concern as to AL efficacy. Monitoring of AL efficacy would help the Lao Government to make decisions on appropriate malaria treatment. Methods The efficacy of a three-day, twice daily oral artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in Xepon District, Savannakhet Province, southern Laos was studied over 42 days follow-up. This was part of a trial of thiamin supplementation in falciparum malaria. Results Of 630 patients with P. falciparum enrolled in the trial of thiamin treatment, 549 (87%, 357 children ≤15 years and 192 adults) were included in this study. The per protocol 42-day cure rates were 97% (524/541) [96% (337/352) for children and 99% (187/189) for adults, p = 0.042]. By conventional intention-to-treat analysis, the 42-day cure rates adjusted for re-infection, were 97% (532/549) [96% (342/357) in children and 99% (190/192) in adults, p = 0.042]. The proportion of patients who remained parasitaemic at day 1 after treatment was significantly higher in children [33% (116/356)] compared to adults [15% (28/192)] (p < 0.001) and only one adult patient had detectable parasitaemia on day 2. There were no serious adverse events. Potential side effects after treatment were reported more commonly in adults (32%) compared to children (15%) (p < 0.001). Patients with recrudescent infections were significantly younger, had longer mean time to fever clearance, and had longer median time to parasite clearance compared to those who were cured. Conclusions The current nationally-recommended anti-malarial treatment (artemether-lumefantrine) remains highly efficacious for the treatment of uncomplicated falciparum malaria five years after introduction in Laos. Regular monitoring is required in case artemisinin-resistant P. falciparum parasites should appear. Trial registration ISRCTN85411059.
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Affiliation(s)
- Mayfong Mayxay
- Wellcome Trust-Mahosot Hospital-Oxford University Tropical Medicine Research Collaboration, Mahosot Hospital, Vientiane, Lao PDR.
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Mallick PK, Joshi H, Valecha N, Sharma SK, Eapen A, Bhatt RM, Srivastava HC, Sutton PL, Dash AP, Bhasin VK. Mutant pfcrt "SVMNT" haplotype and wild type pfmdr1 "N86" are endemic in Plasmodium vivax dominated areas of India under high chloroquine exposure. Malar J 2012; 11:16. [PMID: 22236376 PMCID: PMC3283508 DOI: 10.1186/1475-2875-11-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 01/11/2012] [Indexed: 11/23/2022] Open
Abstract
Background Chloroquine resistance (CQR) phenotype in Plasmodium falciparum is associated with mutations in pfcrt and pfmdr-1 genes. Mutations at amino acid position 72-76 of pfcrt gene, here defined as pfcrt haplotype are associated with the geographic origin of chloroquine resistant parasite. Here, mutations at 72-76 and codon 220 of pfcrt gene and N86Y pfmdr-1 mutation were studied in blood samples collected across 11 field sites, inclusive of high and low P. falciparum prevalent areas in India. Any probable correlation between these mutations and clinical outcome of CQ treatment was also investigated. Methods Finger pricked blood spotted on Whatman No.3 papers were collected from falciparum malaria patients of high and low P. falciparum prevalent areas. For pfcrt haplotype investigation, the parasite DNA was extracted from blood samples and used for PCR amplification, followed by partial sequencing of the pfcrt gene. For pfmdr-1 N86Y mutation, the PCR product was subjected to restriction digestion with AflIII endonuclease enzyme. Results In 240 P. falciparum isolates with reported in vivo CQ therapeutic efficacy, the analysis of mutations in pfcrt gene shows that mutant SVMNT-S (67.50%) and CVIET-S (23.75%) occurred irrespective of clinical outcome and wild type CVMNK-A (7.91%) occurred only in adequate clinical and parasitological response samples. Of 287 P. falciparum isolates, SVMNTS 192 (66.89%) prevailed in all study sites and showed almost monomorphic existence (98.42% isolates) in low P. falciparum prevalent areas. However, CVIETS-S (19.51%) and CVMNK-A (11.84%) occurrence was limited to high P. falciparum prevalent areas. Investigation of pfmdr-1 N86Y mutation shows no correlation with clinical outcomes. The wild type N86 was prevalent in all the low P. falciparum prevalent areas (94.48%). However, mutant N86Y was comparably higher in numbers at the high P. falciparum prevalent areas (42.76%). Conclusions The wild type pfcrt gene is linked to chloroquine sensitivity; however, presence of mutation cannot explain the therapeutic efficacy of CQ in the current scenario of chloroquine resistance. The monomorphic existence of mutant SVMNT haplotype, infer inbreeding and faster spread of CQR parasite in areas with higher P. vivax prevalance and chloroquine exposure, whereas, diversity is maintained in pfcrt gene at high P. falciparum prevalent areas.
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Molecular analysis of pfatp6 and pfmdr1 polymorphisms and their association with in vitro sensitivity in Plasmodium falciparum isolates from the Thai-Myanmar border. Acta Trop 2011; 120:130-5. [PMID: 21777558 DOI: 10.1016/j.actatropica.2011.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 07/02/2011] [Accepted: 07/04/2011] [Indexed: 11/22/2022]
Abstract
The association between pfatp6, pfmdr1 polymorphisms (gene mutation and amplification) and in vitro susceptibility to mefloquine (MQ), artesunate (AS), quinine (QN), and chloroquine (CQ) was investigated in a total of sixty-three Plasmodium falciparum isolates collected from the Thai-Myanmar border. The mutations of pfatp6 at codons R37K, G639D, S769N, and I898I and of pfmdr1 at codons N86Y, Y184F, N1042D, and D1246Y were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Pfatp6 and pfmdr1 gene copy numbers were analyzed by quantitative real time-polymerase chain reaction (qRT-PCR). In vitro susceptibility test was successful in 58 culture-adapted isolates. Median (range) IC(50) values for MQ, AS, QN, and CQ were 28.96 (3.4-100.5), 1.74 (0.8-5.57), 223.9 (14.99-845.47), and 69.93 (9.6-183.18) nM, respectively. There was a significant positive correlation (R(2) = 0.58) of parasite susceptibility to MQ, AS, and QN. Twelve isolates showed marked decline in susceptibility to AS [median (range) IC(50) = 3.78 (3.07-5.57) nM]. Almost all isolates carried wild-type pfatp6 and pfmdr1 alleles at the investigated codons, while only three isolates (5%) carried pfmdr1 mutation alleles at codon 86. Mutation at codon 86 was associated with a significant increase in the susceptibility of parasite isolates to MQ and QN. All of the sixty-three isolates carried only one pfatp6 copy number. Thirty-three out of the 58 isolates showed increase in pfmdr1 gene copies, which was associated with reduced in vitro susceptibility to MQ, AS, and QN. No association between mutation or amplification of pfatp6 gene and in vitro susceptibility of P. falciparum isolates was found.
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Roederer MW, McLeod H, Juliano JJ. Can pharmacogenomics improve malaria drug policy? Bull World Health Organ 2011; 89:838-45. [PMID: 22084530 DOI: 10.2471/blt.11.087320] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 07/05/2011] [Accepted: 07/08/2011] [Indexed: 01/27/2023] Open
Abstract
Coordinated global efforts to prevent and control malaria have been a tour-de-force for public health, but success appears to have reached a plateau in many parts of the world. While this is a multifaceted problem, policy strategies have largely ignored genetic variations in humans as a factor that influences both selection and dosing of antimalarial drugs. This includes attempts to decrease toxicity, increase effectiveness and reduce the development of drug resistance, thereby lowering health care costs. We review the potential hurdles to developing and implementing pharmacogenetic-guided policies at a national or regional scale for the treatment of uncomplicated falciparum malaria. We also consider current knowledge on some component drugs of artemisinin combination therapies and ways to increase our understanding of host genetics, with the goal of guiding policy decisions for drug selection.
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Affiliation(s)
- Mary W Roederer
- Institute of Pharmacogenomics and Individualized Therapy, Eshelman School of Pharmacy, University of North Carolina, 120 Mason Farm Road, Chapel Hill, NC 27599-7361, United States of America.
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Mubjer RA, Adeel AA, Chance ML, Hassan AA. Molecular markers of anti-malarial drug resistance in Lahj Governorate, Yemen: baseline data and implications. Malar J 2011; 10:245. [PMID: 21854642 PMCID: PMC3177815 DOI: 10.1186/1475-2875-10-245] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2011] [Accepted: 08/21/2011] [Indexed: 11/11/2022] Open
Abstract
Background This is an investigation of anti-malarial molecular markers coupled with a therapeutic efficacy test of chloroquine (CQ) against falciparum malaria in an area of unstable malaria in Lahj Governorate, Yemen. The study was aimed at assessment of therapeutic response to CQ and elucidation of baseline information on molecular markers for Plasmodium falciparum resistance against CQ and sulphadoxine/pyrimethamine (SP). Methods Between 2002 and 2003 the field test was conducted according to the standard WHO protocol to evaluate the therapeutic efficacy of CQ in 124 patients with falciparum malaria in an endemic area in Lahj Governorate in Yemen. Blood samples collected during this study were analysed for P. falciparum chloroquine resistance transporter gene (pfcrt)-76 polymorphisms, mutation pfcrt-S163R and the antifolate resistance-associated mutations dihydrofolate reductase (dhfr)-C59R and dihydropteroate synthase (dhps)-K540E. Direct DNA sequencing of the pfcrt gene from three representative field samples was carried out after DNA amplification of the 13 exons of the pfcrt gene. Results Treatment failure was detected in 61% of the 122 cases that completed the 14-day follow-up. The prevalence of mutant pfcrt T76 was 98% in 112 amplified pre-treatment samples. The presence of pfcrt T76 was poorly predictive of in vivo CQ resistance (PPV = 61.8%, 95% CI = 52.7-70.9). The prevalence of dhfr Arg-59 mutation in 99 amplified samples was 5%, while the dhps Glu-540 was not detected in any of 119 amplified samples. Sequencing the pfcrt gene confirmed that Yemeni CQ resistant P. falciparum carry the old world (Asian and African) CQ resistant haplotype CVIETSESI at positions 72,73,74,75,76,220,271, 326 and 371. Conclusion This is the first study to report baseline information on the characteristics and implications of anti-malarial drug resistance markers in Yemen. It is also the first report of the haplotype associated with CQR P. falciparum parasites from Yemen. Mutant pfcrtT76 is highly prevalent but it is a poor predictor of treatment failure in the study population. The prevalence of mutation dhfrArg59 is suggestive of emerging resistance to SP, which is currently a component of the recommended combination treatment of falciparum malaria in Yemen. More studies on these markers are recommended for surveillance of resistance in the study area.
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Affiliation(s)
- Reem A Mubjer
- Genetics and Immunology, Department of Physiological Sciences, Faculty of Medicine and Health Sciences, Aden University, Yemen.
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Identification of a mutant PfCRT-mediated chloroquine tolerance phenotype in Plasmodium falciparum. PLoS Pathog 2010; 6:e1000887. [PMID: 20485514 PMCID: PMC2869323 DOI: 10.1371/journal.ppat.1000887] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 04/01/2010] [Indexed: 11/20/2022] Open
Abstract
Mutant forms of the Plasmodium falciparum transporter PfCRT constitute the key determinant of parasite resistance to chloroquine (CQ), the former first-line antimalarial, and are ubiquitous to infections that fail CQ treatment. However, treatment can often be successful in individuals harboring mutant pfcrt alleles, raising questions about the role of host immunity or pharmacokinetics vs. the parasite genetic background in contributing to treatment outcomes. To examine whether the parasite genetic background dictates the degree of mutant pfcrt-mediated CQ resistance, we replaced the wild type pfcrt allele in three CQ-sensitive strains with mutant pfcrt of the 7G8 allelic type prevalent in South America, the Oceanic region and India. Recombinant clones exhibited strain-dependent CQ responses that ranged from high-level resistance to an incremental shift that did not meet CQ resistance criteria. Nonetheless, even in the most susceptible clones, 7G8 mutant pfcrt enabled parasites to tolerate CQ pressure and recrudesce in vitro after treatment with high concentrations of CQ. 7G8 mutant pfcrt was found to significantly impact parasite responses to other antimalarials used in artemisinin-based combination therapies, in a strain-dependent manner. We also report clinical isolates from French Guiana that harbor mutant pfcrt, identical or related to the 7G8 haplotype, and manifest a CQ tolerance phenotype. One isolate, H209, harbored a novel PfCRT C350R mutation and demonstrated reduced quinine and artemisinin susceptibility. Our data: 1) suggest that high-level CQR is a complex biological process dependent on the presence of mutant pfcrt; 2) implicate a role for variant pfcrt alleles in modulating parasite susceptibility to other clinically important antimalarials; and 3) uncover the existence of a phenotype of CQ tolerance in some strains harboring mutant pfcrt. Plasmodium falciparum resistance to the antimalarial drug chloroquine has been found to result primarily from point mutations in PfCRT, which provide a highly sensitive marker of in vivo treatment failure and in vitro resistance. Debate has nonetheless continued about the singular role of mutant PfCRT and the contribution of the parasite genetic background. To address this, we have generated recombinant P. falciparum lines expressing a mutant pfcrt allele, or the reference wild type allele, in three distinct chloroquine-sensitive strains. Their analysis reveals a spectrum of responses ranging from high-level resistance to a previously unrecognized tolerance phenotype. The latter is characterized by virtually unchanged chloroquine IC50 values, significantly elevated IC90 values, and the ability to recrudesce after exposure to drug concentrations that are lethal to chloroquine-sensitive parasites. This tolerance phenotype was also observed in an isolate from French Guiana, confirming its presence in malaria-endemic regions. Mutant PfCRT significantly affected parasite responses to other antimalarials, including ones used in artemisinin-based combination therapies, in a strain-dependent manner. Our data suggest that successful CQ treatment of drug-resistant parasites is dependent on both host immunity and the strain-dependent extent to which mutant pfcrt imparts resistance.
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Londono BL, Eisele TP, Keating J, Bennett A, Chattopadhyay C, Heyliger G, Mack B, Rawson I, Vely JF, Désinor O, Krogstad DJ. Chloroquine-resistant haplotype Plasmodium falciparum parasites, Haiti. Emerg Infect Dis 2009; 15:735-40. [PMID: 19402959 PMCID: PMC2686998 DOI: 10.3201/eid1505.081063] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Plasmodium falciparum parasites have been endemic to Haiti for >40 years without evidence of chloroquine (CQ) resistance. In 2006 and 2007, we obtained blood smears for rapid diagnostic tests (RDTs) and filter paper blots of blood from 821 persons by passive and active case detection. P. falciparum infections diagnosed for 79 persons by blood smear or RDT were confirmed by PCR for the small subunit rRNA gene of P. falciparum. Amplification of the P. falciparum CQ resistance transporter (pfcrt) gene yielded 10 samples with amplicons resistant to cleavage by ApoI. A total of 5 of 9 samples had threonine at position 76 of pfcrt, which is consistent with CQ resistance (haplotypes at positions 72-76 were CVIET [n = 4] and CVMNT [n = 1]); 4 had only the wild-type haplotype associated with CQ susceptibility (CVMNK). These results indicate that CQ-resistant haplotype P. falciparum malaria parasites are present in Haiti.
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Picot S, Olliaro P, de Monbrison F, Bienvenu AL, Price RN, Ringwald P. A systematic review and meta-analysis of evidence for correlation between molecular markers of parasite resistance and treatment outcome in falciparum malaria. Malar J 2009; 8:89. [PMID: 19413906 PMCID: PMC2681474 DOI: 10.1186/1475-2875-8-89] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 05/04/2009] [Indexed: 01/17/2023] Open
Abstract
Background An assessment of the correlation between anti-malarial treatment outcome and molecular markers would improve the early detection and monitoring of drug resistance by Plasmodium falciparum. The purpose of this systematic review was to determine the risk of treatment failure associated with specific polymorphisms in the parasite genome or gene copy number. Methods Clinical studies of non-severe malaria reporting on target genetic markers (SNPs for pfmdr1, pfcrt, dhfr, dhps, gene copy number for pfmdr1) providing complete information on inclusion criteria, outcome, follow up and genotyping, were included. Three investigators independently extracted data from articles. Results were stratified by gene, codon, drug and duration of follow-up. For each study and aggregate data the random effect odds ratio (OR) with 95%CIs was estimated and presented as Forest plots. An OR with a lower 95th confidence interval > 1 was considered consistent with a failure being associated to a given gene mutation. Results 92 studies were eligible among the selection from computerized search, with information on pfcrt (25/159 studies), pfmdr1 (29/236 studies), dhfr (18/373 studies), dhps (20/195 studies). The risk of therapeutic failure after chloroquine was increased by the presence of pfcrt K76T (Day 28, OR = 7.2 [95%CI: 4.5–11.5]), pfmdr1 N86Y was associated with both chloroquine (Day 28, OR = 1.8 [95%CI: 1.3–2.4]) and amodiaquine failures (OR = 5.4 [95%CI: 2.6–11.3, p < 0.001]). For sulphadoxine-pyrimethamine the dhfr single (S108N) (Day 28, OR = 3.5 [95%CI: 1.9–6.3]) and triple mutants (S108N, N51I, C59R) (Day 28, OR = 3.1 [95%CI: 2.0–4.9]) and dhfr-dhps quintuple mutants (Day 28, OR = 5.2 [95%CI: 3.2–8.8]) also increased the risk of treatment failure. Increased pfmdr1 copy number was correlated with treatment failure following mefloquine (OR = 8.6 [95%CI: 3.3–22.9]). Conclusion When applying the selection procedure for comparative analysis, few studies fulfilled all inclusion criteria compared to the large number of papers identified, but heterogeneity was limited. Genetic molecular markers were related to an increased risk of therapeutic failure. Guidelines are discussed and a checklist for further studies is proposed.
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Affiliation(s)
- Stéphane Picot
- Malaria Research Unit, EA 4170, University Lyon 1, Faculty of Medicine, Lyon, France.
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Mita T, Tanabe K, Kita K. Spread and evolution of Plasmodium falciparum drug resistance. Parasitol Int 2009; 58:201-9. [PMID: 19393762 DOI: 10.1016/j.parint.2009.04.004] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 03/25/2009] [Accepted: 04/16/2009] [Indexed: 11/19/2022]
Abstract
Worldwide spread of Plasmodium falciparum drug resistance to conventional antimalarials, chloroquine and sulfadoxine/pyrimethamine, has been imposing a serious public health problem in many endemic regions. Recent discovery of drug resistance-associated genes, pfcrt, pfmdr1, dhfr, and dhps, and applications of microsatellite markers flanking the genes have revealed the evolution of parasite resistance to these antimalarials and the geographical spread of drug resistance. Here, we review our recent knowledge of the evolution and spread of parasite resistance to chloroquine and sulfadoxine/pyrimethamine. In both antimalarials, resistance appears to be largely explained by the invasion of limited resistant lineages to many endemic regions. However, multiple, indigenous evolutionary origins of resistant lineages have also been demonstrated. Further molecular evolutionary and population genetic approaches will greatly facilitate our understanding of the evolution and spread of parasite drug resistance, and will contribute to developing strategies for better control of malaria.
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Affiliation(s)
- Toshihiro Mita
- Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, School of Medicine, 9-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
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Jalousian F, Dalimi A, Samiee SM, Ghaffarifar F, Soleymanloo F, Naghizadeh R. Mutation in pfmdr1 gene in chloroquine-resistant Plasmodium falciparum isolates, Southeast Iran. Int J Infect Dis 2008; 12:630-4. [DOI: 10.1016/j.ijid.2008.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Revised: 12/11/2007] [Accepted: 01/20/2008] [Indexed: 10/21/2022] Open
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Folarin OA, Gbotosho GO, Sowunmi A, Olorunsogo OO, Oduola AMJ, Happi TC. Chloroquine Resistant Plasmodium falciparum in Nigeria: Relationship between pfcrt and pfmdr1 Polymorphisms, In-Vitro Resistance and Treatment Outcome. ACTA ACUST UNITED AC 2008; 1:74-82. [PMID: 19953193 DOI: 10.2174/1874315300801010074] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study was designed to evaluate the association between polymorphisms in pfcrt and pfmdr1 genes and in-vitro chloroquine (CQ) sensitivity in fresh isolates of P. falciparum and patients' treatment outcome. The modified schizont inhibition assay was used to determine in-vitro sensitivity of P. falciparum. Polymorphisms in pfcrt and pfmdr1 genes were detected using nested PCR and RFLP techniques in 84 P. falciparum isolates obtained from patients with acute uncomplicated malaria.Eighty five percent (71/84) and 15% (13/84) of the parasites were resistant and sensitive in-vitro to CQ respectively. Molecular analysis showed presence of mutant pfcrtT76, pfmdr1Y86 and pfmdr1F184 alleles in 60%, 33% and 14% of the isolates respectively. There was a significant association between in-vitro and in-vivo CQ resistance (p=0.029) and also between the presence of mutant pfcrtT76+pfmdr1 Y86-Y184 haplotype and in-vitro (p=0.013) or in-vivo CQ resistance (p=0.024).Overall results from this study demonstrates that the presence of pfcrtT76+ pfmdr1 Y86-Y184 haplotype in Nigerian isolates of Plasmodium falciparum is predictive of in-vitro and in-vivo CQ resistance and therefore may be useful for monitoring resistance to this drug.
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Affiliation(s)
- O A Folarin
- Malaria Research Laboratories, Institute for Advanced Medical Research and Training (IMRAT), College of Medicine, University of Ibadan, Ibadan, Nigeria
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Monitoring Plasmodium falciparum chloroquine resistance in Yunnan Province, China, 1981-2006. Acta Trop 2008; 108:44-9. [PMID: 18822265 DOI: 10.1016/j.actatropica.2008.08.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Revised: 08/22/2008] [Accepted: 08/27/2008] [Indexed: 11/22/2022]
Abstract
The emergence and spread of drug resistant malaria parasites are an important factor contributing to the global resurgence of malaria, demonstrating the essence of drug resistance surveillance in endemic areas. In the malarious border regions of Yunnan Province, China, we have selected three study sites to monitor in vitro and in vivo resistance of Plasmodium falciparum parasites to chloroquine (CQ) from 1981 to 2006. In vitro studies using the microtest clearly showed high degree of CQ resistance in the early 1980s, when CQ was replaced by artemether monotherapy for falciparum malaria. In subsequent in vitro surveys performed in the early 1990s and 2003-2004, we found reductions in both the concentrations inhibiting 50% parasite growth (IC(50)s) and the percentage of resistant parasites at all study sites, although the degrees of the reduction varied among sites. Even though amodiaquine has never been used in this area, there were consistently high levels of resistance to this drug, confirming crossresistance between CQ and amodiaquine. In vivo clinical studies were consistent with the results of the in vitro assays. The overall rate of resistant clinical cases decreased from 97% in 1981-1983 to 40% in 2005-2006. Collectively, whereas a general trend of reduction in CQ resistance was observed in Yunnan, variations among sites existed in this relatively small area, probably as the result of both geographical heterogeneity of malaria epidemiology in Yunnan and different levels of CQ resistance in neighboring countries.
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Marfurt J, Müller I, Sie A, Oa O, Reeder JC, Smith TA, Beck HP, Genton B. The usefulness of twenty-four molecular markers in predicting treatment outcome with combination therapy of amodiaquine plus sulphadoxine-pyrimethamine against falciparum malaria in Papua New Guinea. Malar J 2008; 7:61. [PMID: 18423045 PMCID: PMC2377269 DOI: 10.1186/1475-2875-7-61] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2007] [Accepted: 04/19/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In Papua New Guinea (PNG), combination therapy with amodiaquine (AQ) or chloroquine (CQ) plus sulphadoxine-pyrimethamine (SP) was introduced as first-line treatment against uncomplicated malaria in 2000. METHODS We assessed in vivo treatment failure rates with AQ+SP in two different areas in PNG and twenty-four molecular drug resistance markers of Plasmodium falciparum were characterized in pre-treatment samples. The aim of the study was to investigate the association between infecting genotype and treatment response in order to identify useful predictors of treatment failure with AQ+SP. RESULTS In 2004, Day-28 treatment failure rates for AQ+SP were 29% in the Karimui and 19% in the South Wosera area, respectively. The strongest independent predictors for treatment failure with AQ+SP were pfmdr1 N86Y (OR = 7.87, p < 0.01) and pfdhps A437G (OR = 3.44, p < 0.01). Mutations found in CQ/AQ related markers pfcrt K76T, A220S, N326D, and I356L did not help to increase the predictive value, the most likely reason being that these mutations reached almost fixed levels. Though mutations in SP related markers pfdhfr S108N and C59R were not associated with treatment failure, they increased the predictive value of pfdhps A437G. The difference in treatment failure rate in the two sites was reflected in the corresponding genetic profile of the parasite populations, with significant differences seen in the allele frequencies of mutant pfmdr1 N86Y, pfmdr1 Y184F, pfcrt A220S, and pfdhps A437G. CONCLUSION The study provides evidence for high levels of resistance to the combination regimen of AQ+SP in PNG and indicates which of the many molecular markers analysed are useful for the monitoring of parasite resistance to combinations with AQ+SP.
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Affiliation(s)
- Jutta Marfurt
- Swiss Tropical Institute, Socinstrasse 57, P,O, Box, CH-4002 Basel, Switzerland.
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Discordant patterns of genetic variation at two chloroquine resistance loci in worldwide populations of the malaria parasite Plasmodium falciparum. Antimicrob Agents Chemother 2008; 52:2212-22. [PMID: 18411325 DOI: 10.1128/aac.00089-08] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in the chloroquine resistance (CQR) transporter gene of Plasmodium falciparum (Pfcrt; chromosome 7) play a key role in CQR, while mutations in the multidrug resistance gene (Pfmdr1; chromosome 5) play a significant role in the parasite's resistance to a variety of antimalarials and also modulate CQR. To compare patterns of genetic variation at Pfcrt and Pfmdr1 loci, we investigated 460 blood samples from P. falciparum-infected patients from four Asian, three African, and three South American countries, analyzing microsatellite (MS) loci flanking Pfcrt (five loci [approximately 40 kb]) and Pfmdr1 (either two loci [approximately 5 kb] or four loci [approximately 10 kb]). CQR Pfmdr1 allele-associated MS haplotypes showed considerably higher genetic diversity and higher levels of subdivision than CQR Pfcrt allele-associated MS haplotypes in both Asian and African parasite populations. However, both Pfcrt and Pfmdr1 MS haplotypes showed similar levels of low diversity in South American parasite populations. Median-joining network analyses showed that the Pfcrt MS haplotypes correlated well with geography and CQR Pfcrt alleles, whereas there was no distinct Pfmdr1 MS haplotype that correlated with geography and/or CQR Pfmdr1 alleles. Furthermore, multiple independent origins of CQR Pfmdr1 alleles in Asia and Africa were inferred. These results suggest that variation at Pfcrt and Pfmdr1 loci in both Asian and African parasite populations is generated and/or maintained via substantially different mechanisms. Since Pfmdr1 mutations may be associated with resistance to artemisinin combination therapies that are replacing CQ, particularly in Africa, it is important to determine if, and how, the genetic characteristics of this locus change over time.
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Fatemeh J, Abdolhosse D, Siamak MS, . GF, Faramarz S, Ramin N. Application of Real-Time PCR for Detection of pfcrt Single Nucleotide Polymorphisms in Plasmodium falciparum in Southeast Iran. JOURNAL OF MEDICAL SCIENCES 2007. [DOI: 10.3923/jms.2007.1082.1087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Viana GMR, Machado RLD, Calvosa VSP, Póvoa MM. Mutations in the pfmdr1, cg2, and pfcrt genes in Plasmodium falciparum samples from endemic malaria areas in Rondonia and Pará State, Brazilian Amazon Region. CAD SAUDE PUBLICA 2007; 22:2703-11. [PMID: 17096048 DOI: 10.1590/s0102-311x2006001200019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2005] [Accepted: 11/08/2005] [Indexed: 11/22/2022] Open
Abstract
The objectives of this study were to investigate the molecular basis for Plasmodium falciparum resistance to chloroquine in isolates from the Brazilian Amazon and to identify polymorphisms in the pfmdr1 gene, codons 184, 1042, and 1246, the kappa and gamma regions of the cg2 gene, and the K76T mutation of the pfcrt gene, in order to calculate the distribution of polymorphism within each target gene, comparing samples from distinct geographic areas, using allele-specific polymerase chain reaction (PCR) for the pfmdr gene and PCR plus restriction fragment length polymorphism (RFLP) for the cg2 and pfcrt genes. The sample consisted of 40 human blood isolates, already collected and morphologically diagnosed as carriers of P. falciparum parasites, from four localities: Porto Velho in Rondonia State and Maraba, Itaituba, and Tailandia in Pará State. Distribution of P. falciparum in vitro chloroquine resistance in the isolates was 100% for pfmdr1, cg2 gamma region, and pfcrt, except for the polymorphism in the cg2 kappa region, which was not found.
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Keen J, Farcas GA, Zhong K, Yohanna S, Dunne MW, Kain KC. Real-time PCR assay for rapid detection and analysis of PfCRT haplotypes of chloroquine-resistant Plasmodium falciparum isolates from India. J Clin Microbiol 2007; 45:2889-93. [PMID: 17609321 PMCID: PMC2045286 DOI: 10.1128/jcm.02291-06] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chloroquine-resistant Plasmodium falciparum (CRPF) malaria isolates in Southeast Asia and sub-Saharan Africa share the same Plasmodium falciparum chloroquine resistance transporter (PfCRT) haplotype (CVIET; amino acids 72 to 76). It is believed that CRPF malaria emerged in Southeast Asia and spread to sub-Saharan Africa via the Indian subcontinent. Based on this assumption, we hypothesized that CRPF isolates in India should possess the same drug resistance haplotype (PfCRT haplotype CVIET) as P. falciparum isolates in Southeast Asia and Africa and that the prevalence of CRPF may be higher and more widespread in India than appreciated. To test this postulate, we utilized a standardized real-time PCR assay to assess the prevalence and distribution of PfCRT haplotypes in P. falciparum isolates (n = 406) collected from Western, Central, and Eastern states in India and compared them to isolates from South America and Africa. Based on the proportion of isolates possessing the molecular marker K76T, the prevalence of chloroquine resistance was high in all five regions of India studied (91%), as well as in Uganda (98%) and Suriname (100%). All isolates from Suriname contained the chloroquine-resistant SVMNT haplotype typical of South American isolates, and 98% of isolates from Uganda possessed the chloroquine-resistant CVIET haplotype characteristic of Southeast Asian/African strains. However, of 246 P. falciparum isolates from across India that contained the molecular marker for chloroquine resistance, 81% contained the SVMNT haplotype. In conclusion, the prevalence of CRPF malaria was high in geographically dispersed regions of India, and the primary haplotype observed, SVMNT, did not support a presumed geographic spread from contiguous Southeast Asia.
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Affiliation(s)
- Jessica Keen
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Canada
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Mayxay M, Pongvongsa T, Phompida S, Phetsouvanh R, White NJ, Newton PN. Diagnosis and management of malaria by rural community health providers in the Lao People's Democratic Republic (Laos). Trop Med Int Health 2007; 12:540-6. [PMID: 17445145 DOI: 10.1111/j.1365-3156.2007.01820.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We assessed the knowledge of malaria diagnosis and management by community health providers in rural Vientiane and Savannakhet Provinces, Lao PDR. Sixty health providers (17 pharmacy owners/drug sellers and 43 village health volunteers) were interviewed. All diagnosed malaria using symptoms and signs only; 14% were aware of >2 criteria for the diagnosis of severe malaria. Although chloroquine and quinine, the then recommended Lao national policy for uncomplicated malaria treatment, were the most common antimalarials prescribed - 65% gave incorrect doses and 70% did not know the side effects. Although not recommended by the then national policy, 27% of the health providers used combinations of antimalarials as they considered monotherapy ineffective. This study strongly suggests that further training of Lao rural health providers in malaria diagnosis and management is needed to improve the quality of health services in areas remote from district hospitals.
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MESH Headings
- Administration, Oral
- Adult
- Antimalarials/administration & dosage
- Antimalarials/adverse effects
- Child
- Chloroquine/administration & dosage
- Chloroquine/adverse effects
- Clinical Competence
- Community Health Services
- Cross-Sectional Studies
- Female
- Health Knowledge, Attitudes, Practice
- Health Personnel/psychology
- Hospitalization
- Humans
- Injections, Intravenous
- Laos/epidemiology
- Malaria, Falciparum/diagnosis
- Malaria, Falciparum/drug therapy
- Malaria, Falciparum/epidemiology
- Male
- Pregnancy
- Pregnancy Complications, Infectious/diagnosis
- Pregnancy Complications, Infectious/drug therapy
- Pregnancy Complications, Infectious/epidemiology
- Quinine/administration & dosage
- Quinine/adverse effects
- Rural Health
- Severity of Illness Index
- Treatment Failure
- Volunteers/psychology
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Affiliation(s)
- Mayfong Mayxay
- Wellcome Trust - Mahosot Hospital - Oxford Tropical Medicine Research Collaboration, Mahosot Hospital, Vientiane, Lao PDR
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Rapid detection of Pfcrt and Pfmdr1 mutations in Plasmodium falciparum isolates by FRET and in vivo response to chloroquine among children from Osogbo, Nigeria. Malar J 2007; 6:41. [PMID: 17428334 PMCID: PMC1855061 DOI: 10.1186/1475-2875-6-41] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Accepted: 04/11/2007] [Indexed: 12/02/2022] Open
Abstract
Background Chloroquine (CQ) has been in use in Africa for a long time. Because of misuse, this drug has now lost its efficacy due to the emergence of resistance strains in most parts of Africa. Recently, it was shown that after chloroquine has been withdrawn from the market, chloroquine-sensitive Plasmodium falciparum re-emerged and chloroquine could again be used successfully as an antimalarial. Surveillance of parasite populations is, therefore, important to decide whether chloroquine could be re-introduced. Methods To estimate the prevalence of the most pivotal polymorphisms, including Pfcrt K76T, Pfmdr1 N86Y and Pfmdr1 Y184F mutations, and their contributions to the outcome of CQ treatment, isolates from Osogbo Western Nigeria were tested using the Fluorescence Resonance Energy Transfer (FRET) method on a real-time PCR instrument. Results 116 children with acute uncomplicated P. falciparum malaria infections were treated with the standard dosage of CQ and followed-up for 28 days. Blood samples were collected on filter paper at enrollment and during follow-up for identification of parasite carrying the chloroquine resistant transporter (pfcrt) and P. falciparum-multi drug resistance (pfmdr1) gene mutations. Parasitological assessment of response to treatment showed that 62% of the patients were cured and 38% failed the CQ treatment. The presence of single mutant pfcrt (T76) alleles (P = 0.003) and in combination with mutant pfmdr1 Y86 (P = 0.028) was significantly associated with in vivo CQR. No other mutation on its own or in combinations was significantly associated with treatment outcome. Mutant pfcrt was more prevalent in both pre- and post-treatment isolates. No association was observed between age or initial level of parasitaemia and chloroquine treatment outcome. Conclusion The result established the usefulness and accuracy of real time PCR in pfcrt and pfmdr1 mutation detection and also give further evidence to the reliability of the pfcrt T76 point mutation as a molecular marker for CQ resistance.
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Microsatellite polymorphism within pfcrt provides evidence of continuing evolution of chloroquine-resistant alleles in Papua New Guinea. Malar J 2007; 6:34. [PMID: 17376240 PMCID: PMC1838424 DOI: 10.1186/1475-2875-6-34] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Accepted: 03/21/2007] [Indexed: 11/21/2022] Open
Abstract
Background Polymorphism in the pfcrt gene underlies Plasmodium falciparum chloroquine resistance (CQR), as sensitive strains consistently carry lysine (K), while CQR strains carry threonine (T) at the codon 76. Previous studies have shown that microsatellite (MS) haplotype variation can be used to study the evolution of CQR polymorphism and to characterize intra- and inter-population dispersal of CQR in Papua New Guinea (PNG). Methods Here, following identification of new polymorphic MS in introns 2 and 3 within the pfcrt gene (msint2 and msint3, respectively), locus-by-locus and haplotype heterozygosity (H) analyses were performed to determine the distribution of this intronic polymorphism among pfcrt chloroquine-sensitive and CQR alleles. Results For MS flanking the pfcrt CQR allele, H ranged from 0.07 (B5M77, -18 kb) to 0.094 (9B12, +2 kb) suggesting that CQ selection pressure was responsible for strong homogenisation of this gene locus. In a survey of 206 pfcrt-SVMNT allele-containing field samples from malaria-endemic regions of PNG, H for msint2 was 0.201. This observation suggests that pfcrt msint2 exhibits a higher level of diversity than what is expected from the analyses of pfcrt flanking MS. Further analyses showed that one of the three haplotypes present in the early 1980's samples has become the predominant haplotype (frequency = 0.901) in CQR parasite populations collected after 1995 from three PNG sites, when CQR had spread throughout malaria-endemic regions of PNG. Apparent localized diversification of pfcrt haplotypes at each site was also observed among samples collected after 1995, where minor CQR-associated haplotypes were found to be unique to each site. Conclusion In this study, a higher level of diversity at MS loci within the pfcrt gene was observed when compared with the level of diversity at pfcrt flanking MS. While pfcrt (K76T) and its immediate flanking region indicate homogenisation in PNG CQR parasite populations, pfcrt intronic MS variation provides evidence that the locus is still evolving. Further studies are needed to determine whether these intronic MS introduce the underlying genetic mechanisms that may generate pfcrt allelic diversity.
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Mayxay M, Thongpraseuth V, Khanthavong M, Lindegårdh N, Barends M, Keola S, Pongvongsa T, Phompida S, Phetsouvanh R, Stepniewska K, White NJ, Newton PN. An open, randomized comparison of artesunate plus mefloquine vs. dihydroartemisinin–piperaquine for the treatment of uncomplicated Plasmodium falciparum malaria in the Lao People's Democratic Republic (Laos). Trop Med Int Health 2006; 11:1157-65. [PMID: 16903879 DOI: 10.1111/j.1365-3156.2006.01671.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To determine the efficacy and safety of oral dihydroartemisinin-piperaquine (DP, Artekin) in the treatment of uncomplicated Plasmodium falciparum malaria in southern Laos. METHODS An open, randomized clinical trial of oral artesunate-mefloquine (AM) vs. DP in 220 patients with acute uncomplicated falciparum malaria in Savannakhet Province, Laos. RESULTS The 42-day cure rates (95% CI), as determined by survival analysis and adjusted for reinfection, were excellent and similar for the two groups [99 (94-100)% and 100 (100-100)% for AM and DP, respectively]. The median (range) fever and parasite clearance times for the AM and DP groups were also similar [20 (4-63) h and 2 (1-4) days vs. 20 (7-57) and 2 (1-4) days, logrank P = 0.4 and 0.17, respectively]. There were more patients with at least one potential side effect following treatment in the AM group when compared with the DP group [64/110 (58%) vs. 48/110 (44%), respectively, P = 0.031]. CONCLUSION Dihydroartemisinin-piperaquine did not have superior efficacy to AM for the treatment of uncomplicated falciparum malaria in Laos but was associated with fewer adverse effects.
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Affiliation(s)
- M Mayxay
- Wellcome Trust, Mahosot Hospital, Oxford Tropical Medicine Research Collaboration, Mahosot Hospital, Vientiane, Lao PDR
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Happi CT, Gbotosho GO, Folarin OA, Sowunmi A, Bolaji OM, Fateye BA, Kyle DE, Milhous W, Wirth DF, Oduola AMJ. Linkage disequilibrium between two distinct loci in chromosomes 5 and 7 of Plasmodium falciparum and in vivo chloroquine resistance in Southwest Nigeria. Parasitol Res 2006; 100:141-8. [PMID: 16874478 DOI: 10.1007/s00436-006-0246-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Accepted: 05/22/2006] [Indexed: 10/24/2022]
Abstract
Chloroquine (CQ) resistance in Plasmodium falciparum is associated with polymorphisms in loci on pfcrt and pfmdr1 genes. In this study, we determined the association and linkage disequilibrium between in vivo CQ resistance and P. falciparum polymorphisms in pfcrt gene at codon 76 and pfmdr1 gene at codon 86 in isolates obtained from 111 children with acute uncomplicated falciparum malaria in Nigeria. Patients were treated with standard dosage of CQ and followed up for 28 days. Filter paper samples were collected at enrollment and during follow-up for parasites genotypes and identification of pfcrt and pfmdr1 mutations. Association and linkage disequilibrium between mutant pfcrtT76 and pfmdr1Y86 alleles in pretreatment isolates of P. falciparum was determined. Fifty-five out of the 111 patients (49.5%) failed treatment. Single mutant pfcrtT76 or pfmdr1Y86 alleles were found in 55 out of 111 P. falciparum isolates screened at enrollment. Of these 55 isolates, the mutant pfcrtT76 and pfmdr1Y86 alleles were found in 84%. Both mutant pfcrtT76 (p=0.0196) and pfmdr1Y86 (p=0.000042) alleles were associated with in vivo CQ resistance. In addition, the mutant pfcrtT76 (p=0.047) and pfmdr1Y86 (p=0.006) alleles were significantly selected by CQ in patients who failed treatment. Association analysis between paired single alleles at pfcrt and pfmdr1 loci showed a significant association (p=0.0349 and chi(2)=4.45) between the pfcrt T76 allele on chromosome 7 and the pfmdr1Y86 allele on chromosome 5 and that these two mutant alleles were in linkage disequilibrium (p=0.000, D'=0.64, and r(2)=0.28). Considering the high level of CQ resistance and drug use in the study area, the observed linkage disequilibrium between the mutant pfcrtT76 and pfmdr1Y86 alleles is maintained epistatically through directional CQ selective pressure.
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Affiliation(s)
- C T Happi
- Malaria Research Laboratories, Institute for Advanced Medical Research and Training, College of Medicine, University of Ibadan, Ibadan, Nigeria.
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Plowe CV. Antimalarial drug resistance in Africa: strategies for monitoring and deterrence. Curr Top Microbiol Immunol 2006; 295:55-79. [PMID: 16265887 DOI: 10.1007/3-540-29088-5_3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Despite the initiation in 1998 by the World Health Organization of a campaign to 'Roll Back Malaria', the rates of disease and death caused by Plasmodium falciparum malaria in sub-Saharan Africa are growing. Drug resistance has been implicated as one of the main factors in this disturbing trend. The efforts of international agencies, governments, public health officials, advocacy groups and researchers to devise effective strategies to deter the spread of drug resistant malaria and to ameliorate its heavy burden on the people of Africa have not succeeded. This review will not attempt to describe the regional distribution of drug resistant malaria in Africa in detail, mainly because information on resistance is limited and has been collected using different methods, making it difficult to interpret. Instead, the problems of defining and monitoring resistance and antimalarial drug treatment outcomes will be discussed in hopes of clarifying the issues and identifying ways to move forward in a more coordinated fashion. Strategies to improve measurement of resistance and treatment outcomes, collection and use of information on resistance, and potential approaches to deter and reduce the impact of resistance, will all be considered. The epidemiological setting and the goals of monitoring determine how antimalarial treatment responses should be measured. Longitudinal studies, with incidence of uncomplicated malaria episodes as the primary endpoint, provide the best information on which to base treatment policy changes, while simpler standard in vivo efficacy studies are better suited for ongoing efficacy monitoring. In the absence of an ideal antimalarial combination regimen, different treatment alternatives are appropriate in different settings. But where chloroquine has failed, policy changes are long overdue and action must be taken now.
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Affiliation(s)
- C V Plowe
- Malaria Section, Center for Vaccine Development, University of Maryland School of Medicine, 685 West Baltimore Street, HSF1-480, Baltimore, MA 21201, USA.
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Uhlemann AC, Krishna S. Antimalarial multi-drug resistance in Asia: mechanisms and assessment. Curr Top Microbiol Immunol 2006; 295:39-53. [PMID: 16265886 DOI: 10.1007/3-540-29088-5_2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The emergence and spread of drug-resistant parasites poses a major problem for management of Plasmodium falciparum malaria in endemic areas. Nowhere is this more apparent than in southeast Asia, where multi-drug resistance to chloroquine and sulfadoxine-pyrimethamine was exacerbated when mefloquine monotherapy began failing in the 1980s. A better understanding of mechanisms of (multi-) drug resistance is urgently warranted to monitor and guide antimalarial chemotherapy regimens more efficiently. Here we review recent advances on identification of molecular markers that can be employed in predicting in vitro and in vivo resistance in southeast Asia. Examples include amplification of PfMDR1 (P. falciparum multi-drug resistant gene 1) and mefloquine, K76T PfCRT and chloroquine, as well as mutations in the dihydroperoate synthase and dihydrofolate reductase genes and the antifolate class of drugs.
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Affiliation(s)
- A C Uhlemann
- Division of Cellular and Molecular Medicine, Centre for Infection, St. George's University of London, Cranmer Terrace, London SW17 ORE, UK
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Mita T, Kaneko A, Hombhanje F, Hwaihwanje I, Takahashi N, Osawa H, Tsukahara T, Masta A, Lum JK, Kobayakawa T, Ishizaki T, Björkman A. Role of pfmdr1 mutations on chloroquine resistance in Plasmodium falciparum isolates with pfcrt K76T from Papua New Guinea. Acta Trop 2006; 98:137-44. [PMID: 16620743 DOI: 10.1016/j.actatropica.2006.03.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Revised: 03/21/2006] [Accepted: 03/21/2006] [Indexed: 11/27/2022]
Abstract
The N86Y mutation in pfmdr1 is reported to play an additional role for the chloroquine resistance in Plasmodium falciparum isolates. However, not much has been done to clarify whether this mutation augments the level of chloroquine resistance in the isolates harboring pfcrt K76T mutation. We compared the in vitro chloroquine efficacy between pfcrt K76T mutant parasites with or without N86Y mutation from Papua New Guinea. A total of 57 isolates (4% sensitive, 14% borderline, and 82% resistant) were successfully tested in vitro for chloroquine sensitivity. We found a slightly higher effective concentration of chloroquine needed to inhibit P. falciparum by 50% (mean EC50=107 nM) in isolates with the pfcrt K76T+pfmdr1 N86Y than that in isolates with the pfcrt K76T+pfmdr1 N86 (EC50=88 nM), but this difference was not statistically significant. A significant non-random association was observed between the pfcrt K76T and pfmdr1 N86Y alleles. Our results suggest that the pfmdr1 N86Y mutation plays a compensatory role to chloroquine-resistant isolates under a chloroquine pressure while it may also augment the level of chloroquine resistance in the K76T parasites to a small extent.
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Affiliation(s)
- Toshihiro Mita
- Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo 162-8666, Japan.
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Farcas GA, Soeller R, Zhong K, Zahirieh A, Kain KC. Real-Time Polymerase Chain Reaction Assay for the Rapid Detection and Characterization of Chloroquine-Resistant Plasmodium falciparum Malaria in Returned Travelers. Clin Infect Dis 2006; 42:622-7. [PMID: 16447106 DOI: 10.1086/500134] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2005] [Accepted: 10/16/2005] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND Imported drug-resistant malaria is a growing problem in industrialized countries. Rapid and accurate diagnosis is essential to prevent malaria-associated mortality in returned travelers. However, outside of a limited number of specialized centers, the microscopic diagnosis of malaria is slow, unreliable, and provides little information about drug resistance. Molecular diagnostics have the potential to overcome these limitations. OBJECTIVE We developed and evaluated a rapid, real-time polymerase chain reaction (PCR) assay to detect Plasmodium falciparum malaria and chloroquine (CQ)-resistance determinants in returned travelers who are febrile. METHODS A real-time PCR assay based on detection of the K76T mutation in PfCRT (K76T) of P. falciparum was developed on a LightCycler platform (Roche). The performance characteristics of the real-time assay were compared with those of the nested PCR-restriction fragment-length polymorphism (RFLP) and the sequence analyses of samples obtained from 200 febrile returned travelers, who included 125 infected with P. falciparum (48 of whom were infected CQ-susceptible [K76] and 77 of whom were CQ-resistant [T76] P. falciparum), 22 infected with Plasmodium vivax, 10 infected with Plasmodium ovale, 3 infected with Plasmodium malariae malaria, and 40 infected with other febrile syndromes. All patient samples were coded, and all analyses were performed blindly. RESULTS The real-time PCR assay detected multiple pfcrt haplotypes associated with CQ resistance in geographically diverse malaria isolates acquired by travelers. Compared with nested-PCR RFLP (the reference standard), the real-time assay was 100% sensitive and 96.2% specific for detection of the P. falciparum K76T mutation. CONCLUSION This assay is rapid, sensitive, and specific for the detection and characterization of CQ-resistant P. falciparum malaria in returned travelers. This assay is automated, standardized, and suitable for routine use in clinical diagnostic laboratories.
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Affiliation(s)
- Gabriella A Farcas
- Tropical Disease Unit, University Health Network-Toronto General Hospital, Toronto, Ontario, Canada
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Dittrich S, Alifrangis M, Stohrer JM, Thongpaseuth V, Vanisaveth V, Phetsouvanh R, Phompida S, Khalil IF, Jelinek T. Falciparum malaria in the north of Laos: the occurrence and implications of the Plasmodium falciparum chloroquine resistance transporter (pfcrt) gene haplotype SVMNT. Trop Med Int Health 2006; 10:1267-70. [PMID: 16359407 DOI: 10.1111/j.1365-3156.2005.01514.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE The Pfcrt-gene encodes a transmembrane protein located in the Plasmodium falciparum digestive vacuole. Chloroquine resistant (CQR) strains of African and Southeast Asian origin carry the Pfcrt-haplotype (c72-76) CVIET, whereas most South American and Papua New Guinean CQR stains carry the SVMNT haplotype. METHOD Eighty-eight samples from an area with reported in vivo Chloroquine and in vitro Amodiaquine-resistance were screened for the K76T mutation and their Pfcrt-haplotype (c72-76) using a new SSOP-ELISA. RESULTS Hundred percent of the analysed samples showed the K76T mutation which is highly associated with in vivo drug failure. This very high rate of a CQR-marker is alarming in an area were CQ is still used as first line drug. The distribution of the three main Pfcrt-haplotypes was as follows: 68% CVIET, 31% SVMNT, 0% CVMNT. CONCLUSIONS These data show, for the first time, the South American/PNG -haplotype (SVMNT) on mainland Southeast Asia. SVMNT-haplotype and others might be associated with a decreased efficacy of Amodiaquine and could therefore be potential markers for of amodiaquine resistance (AQR). If there is a correlation between AQR and the SVMNT-haplotype as suggested, 31% prevalence of a potential resistance marker is cause for concern.
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Tagelsir N, Ibrahim Z, Medani A, Salih O, Hamad A, Giha H, El-Agib A, Khan B, Saeed N, Ibrahim M. High frequency of Plasmodium falciparum PfCRT K76T and PfpghN86Y in patients clearing infection after chloroquine treatment in the Sudan. Acta Trop 2006; 97:19-25. [PMID: 16171768 DOI: 10.1016/j.actatropica.2005.07.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2004] [Revised: 07/11/2005] [Accepted: 07/28/2005] [Indexed: 10/25/2022]
Abstract
The clinical response following treatment with chloroquine, and the prevalence of two Plasmodium falciparum DNA polymorphisms known to associate with drug resistance, namely PfCRT K76T and Pfpgh N86Y were investigated in two sites in central and eastern Sudan. Patient's sensitivity to chloroquine was determined according to the standard in vivo test as recommended by the WHO protocol in days 0, 3, 7 and 14, respectively. Clinical un-responsiveness was 75.9% in Gadaref in eastern Sudan and 32.1% in Haj Yousif of the Khartoum state. Difference between the two sites in treatment outcome is not tantamount to allele frequency and genotype distribution of neither Pfcrt K76T nor PfpghN86Y. All post treatment samples in the two areas were carrying the mutant allele of Pfcrt K76T. The higher frequency of PfpghN86Y in Haj Yousif (0.86) than Gadaref (0.72), where chloroquine resistance is higher suggests a minor role, if any, for PfpghN86Y in resistance to chloroquine. Age effect on the clearance of parasitemia was evident in both areas, more significantly though in Gedaref (P<0.000) than Haj Yousif (P=0.043) These results add to reports in the literature, pointing to the complexity of factors that may contribute to a clinical outcome following chloroquine treatment, particularly, in this case are elements of the host immunity that are yet to be identified.
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Gascón J, Mayor A, Mühlberger N, Peyerl-Hoffmann G, Oliveira I, Dobaño C, Jelinek T, Corachan M. [Molecular epidemiological surveillance of markers for antimalarial drugs in Plasmodium falciparum isolates imported to Barcelona, Spain]. Med Clin (Barc) 2005; 125:286-9. [PMID: 16159551 DOI: 10.1157/13078421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
BACKGROUND AND OBJECTIVE There have been described compelling correlations between mutations in some Plasmodium falciparum genes and resistance to antimalarial drugs. To apply molecular techniques in the mechanisms of epidemiological surveillance in the Hospital Clínic of Barcelona and to map potential levels of resistance, we investigated the presence of mutations in the relevant codons of genes associated with resistance in P. falciparum isolates imported by travellers. PATIENTS AND METHOD The genes pfctr, pfmdr1, dhfr, dhps and cytochrome b were analyzed by PCR and enzymatic restriction in P. falciparum isolates from 53 persons attending the Tropical Medicine Department after a trip to a malaria endemic area. RESULTS 63% of patients were infected with a P. falciparum isolate with the K76T mutation in pfctr. Tyr86 in pfmdr1 was found in 54% of the isolates. Mutations in codons 51, 59 and 108 in dhfr were found in 33%, 49% and 44% of the isolates, respectively. Mutations in codons 436, 437 and 540 in dhps were found in 35%, 35% and 8.5% of the isolates. 30% of travellers were infected by parasites displaying 3 or more mutations in any of the codons of dhps and dhfr. None of the patients had a mutation in the Tyr268 codon of the cytochrome B gene. CONCLUSIONS The high prevalence of mutations in the imported isolates suggests a fast development and expansion of resistance against most of the antimalarial drugs commonly used. The concurrence of more than one mutation in different loci suggests the expansion of multiple resistances.
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Affiliation(s)
- Joaquim Gascón
- Centro de Salud Internacional, IDIBAPS, Hospital Clínic de Barcelona, Barcelona, Spain.
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Nash D, Nair S, Mayxay M, Newton PN, Guthmann JP, Nosten F, Anderson TJ. Selection strength and hitchhiking around two anti-malarial resistance genes. Proc Biol Sci 2005; 272:1153-61. [PMID: 16024377 PMCID: PMC1559806 DOI: 10.1098/rspb.2004.3026] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Neutral mutations may hitchhike to high frequency when they are situated close to sites under positive selection, generating local reductions in genetic diversity. This process is thought to be an important determinant of levels of genomic variation in natural populations. The size of genome regions affected by genetic hitchhiking is expected to be dependent on the strength of selection, but there is little empirical data supporting this prediction. Here, we compare microsatellite variation around two drug resistance genes (chloroquine resistance transporter (pfcrt), chromosome 7, and dihydrofolate reductase (dhfr), chromosome 4) in malaria parasite populations exposed to strong (Thailand) or weak selection (Laos) by anti-malarial drugs. In each population, we examined the point mutations underlying resistance and length variation at 22 (chromosome 4) or 25 (chromosome 7) microsatellite markers across these chromosomes. All parasites from Thailand carried the K76T mutation in pfcrt conferring resistance to chloroquine (CQ) and 2-4 mutations in dhfr conferring resistance to pyrimethamine. By contrast, we found both wild-type and resistant alleles at both genes in Laos. There were dramatic differences in the extent of hitchhiking in the two countries. The size of genome regions affected was smaller in Laos than in Thailand. We observed significant reduction in variation relative to sensitive parasites for 34-64 kb (2-4 cM) in Laos on chromosome 4, compared with 98-137 kb (6-8 cM) in Thailand. Similarly, on chromosome 7, we observed reduced variation for 34-69 kb (2-4 cM) around pfcrt in Laos, but for 195-268 kb (11-16 cM) in Thailand. Reduction in genetic variation was also less extreme in Laos than in Thailand. Most loci were monomorphic in a 12 kb region surrounding both genes on resistant chromosomes from Thailand, whereas in Laos, even loci immediately proximal to selective sites showed some variation on resistant chromosomes. Finally, linkage disequilibrium (LD) decayed more rapidly around resistant pfcrt and dhfr alleles from Laos than from Thailand. These results demonstrate that different realizations of the same selective sweeps may vary considerably in size and shape, in a manner broadly consistent with selection history. From a practical perspective, genomic regions containing resistance genes may be most effectively located by genome-wide association in populations exposed to strong drug selection. However, the lower levels of LD surrounding resistance alleles in populations under weak selection may simplify identification of functional mutations.
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Affiliation(s)
- Denae Nash
- Southwest Foundation for Biomedical Research (SFBR)PO Box 760549, San Antonio, TX 78245, USA
- Our Lady of the Lake UniversitySan Antonio, TX 78207, USA
| | - Shalini Nair
- Southwest Foundation for Biomedical Research (SFBR)PO Box 760549, San Antonio, TX 78245, USA
| | - Mayfong Mayxay
- Faculty of MedicineNational University of LaosVientiane, Lao PDR
- Wellcome Trust-Mahosot-Oxford Tropical Medicine Research CollaborationMahosot HospitalVientiane, Lao PDR
| | - Paul N Newton
- Wellcome Trust-Mahosot-Oxford Tropical Medicine Research CollaborationMahosot HospitalVientiane, Lao PDR
| | - Jean-Paul Guthmann
- Epicentre (Médecins Sans Frontières-France)8 rue Saint Sabin, 75011 Paris, France
| | - François Nosten
- 6 Shoklo Malaria Research Unit (SMRU)Mae Sot, Tak, Thailand
- Faculty of Tropical MedicineMahidol UniversityBangkok, Thailand
- Centre for Clinical Vaccinology and Tropical MedicineChurchill HospitalOxford OX3 7LJ, UK
| | - Tim J.C Anderson
- Southwest Foundation for Biomedical Research (SFBR)PO Box 760549, San Antonio, TX 78245, USA
- Author for correspondence ()
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Sarr O, Myrick A, Daily J, Diop BM, Dieng T, Ndir O, Sow PS, Mboup S, Wirth DF. In vivo and in vitro analysis of chloroquine resistance in Plasmodium falciparum isolates from Senegal. Parasitol Res 2005; 97:136-40. [PMID: 15986248 PMCID: PMC2579896 DOI: 10.1007/s00436-005-1406-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Accepted: 05/06/2005] [Indexed: 11/26/2022]
Abstract
To determine the predictive value of chloroquine (CQ) resistance markers in Senegal, Plasmodium falciparum DNA polymorphisms in pfmdr1and pfcrt were examined in relation to clinical outcome. Despite CQ treatment, 17% of patients had parasitemia after 28 days. Examination of molecular markers of CQ resistance revealed that 64% of all isolates had the T76 resistant allele at the pfcrt locus, while 30% carried the Y86 resistant allele at the pfmdr1 locus. The pfcrt T76 allele was present not only in all in vivo resistant isolates, 89% of in vitro resistant isolates, but also in 35% of in vitro sensitive isolates. The pfmdr1 N86Y polymorphism did not correlate with in vitro or in vivo CQ resistance. Our data suggest that the pfcrt T76 allele alone is required but not a sufficient predictor for in vivo CQ resistance.
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Affiliation(s)
- Ousmane Sarr
- Laboratory of Bacteriology and Virology, Hopital Aristide Le Dantec, Dakar, Senegal, USA
| | - Alissa Myrick
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - Johanna Daily
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - Bernard M. Diop
- Infectious Diseases Clinic, Fann Hospital, Dakar, Senegal, USA
| | - Therese Dieng
- Laboratory of Parasitology, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal, USA
| | - Omar Ndir
- Laboratory of Parasitology, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal, USA
| | - Pape Salif Sow
- Infectious Diseases Clinic, Fann Hospital, Dakar, Senegal, USA
| | - Souleymane Mboup
- Laboratory of Bacteriology and Virology, Hopital Aristide Le Dantec, Dakar, Senegal, USA
| | - Dyann F. Wirth
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA, E-mail: , Tel.: +1-617-4321563, Fax: +1-617-4324766
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Abstract
The emergence of drug-resistance poses a major obstacle to the control of malaria. A homolog of the major multidrug-transporter in mammalian cells was identified, Plasmodium falciparum multidrug resistance protein-1, pfmdr1, also known as the P-glycoprotein homolog 1, Pgh-1. Several studies have demonstrated strong, although incomplete, associations between resistance to the widely used antimalarial drug chloroquine and mutation of the pfmdr1 gene in both laboratory and field isolates. Genetic studies have confirmed a link between mutation of the pfmdr1 gene and chloroquine-resistance. Although not essential for chloroquine-resistance, pfmdr1 plays a role in modulating levels of resistance. At the same time it appears to be a significant component in resistance to the structurally related drug quinine. A strong association has been observed between possession of the wildtype form of pfmdr1, amplification of pfmdr1 and resistance to hydrophobic drugs such as the arylaminoalcohol mefloquine and the endoperoxide artemisinin derivatives in field isolates. This is supported by genetic studies. The arylaminoalcohol and endoperoxide drugs are structurally unrelated drugs and this resistance resembles true multidrug resistance. Polymorphism in pfmdr1 and gene amplification has been observed throughout the world and their usefulness in predicting resistance levels is influenced by the history of drug selection of each population.
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Ranjit MR, Das A, Chhotray GP, Roth RN, Kar SK. The PfCRT (K76T) point mutation in Plasmodium falciparum, and its usefulness for monitoring chloroquine resistance. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2005; 98:879-82. [PMID: 15667720 DOI: 10.1179/000349804x3162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Affiliation(s)
- M R Ranjit
- Regional Medical Research Centre (Indian Council of Medical Research), Chandrasekharpur, Bhubaneswar - 751023, Orissa, India.
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HATABU TOSHIMITSU, VANISAVETH VIENGXAY, TAGUCHI NAO, KOBAYASHI JUN, MANNOOR MKAIISSAR, WATANABE HISAMI, TOMA HIROMU, PHOMPIDA SAMLANE, KANO SHIGEYUKI. A PILOT FIELD SURVEY ON THE IN VITRO DRUG SUSCEPTIBILITY OF PLASMODIUM FALCIPARUM IN LAO PDR. Trop Med Health 2005. [DOI: 10.2149/tmh.33.103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Wilson PE, Kazadi W, Kamwendo DD, Mwapasa V, Purfield A, Meshnick SR. Prevalence of pfcrt mutations in Congolese and Malawian Plasmodium falciparum isolates as determined by a new Taqman assay. Acta Trop 2005; 93:97-106. [PMID: 15589802 DOI: 10.1016/j.actatropica.2004.09.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 09/16/2004] [Accepted: 09/23/2004] [Indexed: 11/21/2022]
Abstract
A real-time PCR assay was developed to detect the K76T point mutation in the Plasmodium falciparum putative chloroquine resistance transporter gene. The assay was used with malaria positive clinical isolates from Rutshuru in the eastern part of the Democratic Republic of the Congo (DRC) and from Malawi. The K76T mutation was found in 52/56 (93%) clinical isolates from the DRC, where chloroquine resistance is high, but in none of the 12 isolates tested from Malawi where chloroquine is now rarely used. Sixteen percent of specimens from the DRC had detectable levels of both wild-type and mutant alleles. The real-time PCR results were compared to results from a nested allele-specific PCR assay and from direct DNA sequencing. Using allele-specific PCR as the reference method, the new assay is 100% sensitive and specific towards the mutant allele. In addition to its low per-test cost, the new assay is fast, easily automated, sensitive and well-suited to large-scale epidemiological studies.
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Affiliation(s)
- Paul E Wilson
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, CB 7290, Chapel Hill, NC 27599, USA
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Stepniewska K, Taylor WRJ, Mayxay M, Price R, Smithuis F, Guthmann JP, Barnes K, Myint HY, Adjuik M, Olliaro P, Pukrittayakamee S, Looareesuwan S, Hien TT, Farrar J, Nosten F, Day NPJ, White NJ. In vivo assessment of drug efficacy against Plasmodium falciparum malaria: duration of follow-up. Antimicrob Agents Chemother 2004; 48:4271-80. [PMID: 15504852 PMCID: PMC525402 DOI: 10.1128/aac.48.11.4271-4280.2004] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 02/05/2004] [Accepted: 05/08/2004] [Indexed: 11/20/2022] Open
Abstract
To determine the optimum duration of follow-up for the assessment of drug efficacy against Plasmodium falciparum malaria, 96 trial arms from randomized controlled trials (RCTs) with follow-up of 28 days or longer that were conducted between 1990 and 2003 were analyzed. These trials enrolled 13,772 patients, and participating patients comprised 23% of all patients enrolled in RCTs over the past 40 years; 61 (64%) trial arms were conducted in areas where the rate of malaria transmission was low, and 58 (50%) trial arms were supported by parasite genotyping to distinguish true recrudescences from reinfections. The median overall failure rate reported was 10% (range, 0 to 47%). The widely used day 14 assessment had a sensitivity of between 0 and 37% in identifying treatment failures and had no predictive value. Assessment at day 28 had a sensitivity of 66% overall (28 to 100% in individual trials) but could be used to predict the true failure rate if either parasite genotyping was performed (r(2) = 0.94) or if the entomological inoculation rate was known. In the assessment of drug efficacy against falciparum malaria, 28 days should be the minimum period of follow-up.
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Affiliation(s)
- Kasia Stepniewska
- Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd., Bangkok 10400, Thailand
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Mbaisi A, Liyala P, Eyase F, Achilla R, Akala H, Wangui J, Mwangi J, Osuna F, Alam U, Smoak BL, Davis JM, Kyle DE, Coldren RL, Mason C, Waters NC. Drug susceptibility and genetic evaluation of Plasmodium falciparum isolates obtained in four distinct geographical regions of Kenya. Antimicrob Agents Chemother 2004; 48:3598-601. [PMID: 15328137 PMCID: PMC514731 DOI: 10.1128/aac.48.9.3598-3601.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The drug resistance profiles of Plasmodium falciparum isolated from four regions in Kenya were analyzed for drug resistance profiles. We observed variability in resistance to a broad range of antimalarial drugs across Kenya as determined from in vitro drug susceptibility screening and genotyping analysis.
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Mayxay M, Khanthavong M, Lindegårdh N, Keola S, Barends M, Pongvongsa T, Yapom R, Annerberg A, Phompida S, Phetsouvanh R, White NJ, Newton PN. Randomized Comparison of Chloroquine plus Sulfadoxine-Pyrimethamine versus Artesunate plus Mefloquine versus Artemether-Lumefantrine in the Treatment of Uncomplicated Falciparum Malaria in the Lao People's Democratic Republic. Clin Infect Dis 2004; 39:1139-47. [PMID: 15486837 DOI: 10.1086/424512] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2004] [Accepted: 05/25/2004] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Recent clinical trials in the Lao People's Democratic Republic have demonstrated that chloroquine and sulfadoxine-pyrimethamine, which are national malaria treatment policy, are no longer effective in the treatment of uncomplicated Plasmodium falciparum malaria. METHODS A randomized comparison of 3 oral antimalarial combinations--chloroquine plus sulfadoxine-pyrimethamine versus artesunate plus mefloquine versus artemether-lumefantrine--with 42-day follow-up period, was conducted among 330 patients with acute uncomplicated falciparum malaria in southern Laos. RESULTS The 42-day cure rates, as determined by intention-to-treat analysis and adjusted for reinfection, were 100%, 97%, and 93% for the groups receiving artesunate plus mefloquine, artemether-lumefantrine, and chloroquine plus sulfadoxine-pyrimethamine, respectively. Of 8 patients receiving chloroquine plus sulfadoxine-pyrimethamine who experienced treatment failure, 6 had early treatment failure. The mean parasite clearance time was significantly longer in patients treated with chloroquine plus sulfadoxine-pyrimethamine (2.9 days; 95% confidence interval [CI], 2.8-3.0 days) than in those treated with artesunate plus mefloquine (2.07 days; 95% CI, 2.0-2.1 days; P<.001) and artemether-lumefantrine (2.08 days; 95% CI, 2.0-2.1 days; P<.001). Cure rates with artemether-lumefantrine were high despite low mean daily dietary fat intake (13.8 g; 95% CI, 12.5-15.1 g) and day 7 plasma lumefantrine concentrations (0.47 mu g/mL; 95% CI, 0.38-0.56 mu g/mL). CONCLUSION Oral artesunate plus mefloquine and artemether-lumefantrine are highly effective for the treatment of uncomplicated falciparum malaria in Laos.
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Affiliation(s)
- Mayfong Mayxay
- Wellcome Trust-Mahosot Hospital, Oxford Tropical Medicine Research Collaboration, Vientiane, Lao PDR
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González IJ, Varela RE, Murillo C, Ferro BE, Salas J, Giraldo LE, Zalis MG, Saravia NG. Polymorphisms in cg2 and pfcrt genes and resistance to chloroquine and other antimalarials in vitro in Plasmodium falciparum isolates from Colombia. Trans R Soc Trop Med Hyg 2004; 97:318-24. [PMID: 15228252 DOI: 10.1016/s0035-9203(03)90160-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Polymorphisms in Plasmodium falciparum cg2 and pfcrt genes and their association with chloroquine resistance in vitro in Colombian parasites were evaluated in this study. Association of chloroquine resistance with resistance to other antimalarial drugs in vitro was also examined. Polymerase chain reactions (PCR) for kappa and omega cg2 regions and nested PCR and digestion with ApoI enzyme for K-76T pfcrt point mutation defined corresponding polymorphisms in 83 samples collected between 1995 and 1999. The isotopic microtest was used to evaluate sensitivity in vitro in a subgroup of 18 isolates. The predominant cg2 pattern observed was 13K/14omega repeats (46/83 [55.4%]) and all samples presented the K-76T mutant allele. Seventy-eight percent of samples were resistant to chloroquine in vitro, 35.3% to amodiaquine, 16.7% to mefloquine, and 5.6% to quinine. Significant correlations (P < 0.05) were observed between the IC50s of chloroquine and arteether, and among IC50s of arteether, mefloquine, and quinine. These results suggest the development of multiple and cross-resistance of Colombian P. falciparum isolates to second- and third-line antimalarials and new alternative drugs.
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Affiliation(s)
- Iveth J González
- Centro Internacional de Entrenamiento e Investigaciones Médicas (CIDEIM), Avenida IN # 3-03, Cali, Colombia.
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