Leishmania (Viannia) subgenus kDNA amplification for the diagnosis of mucosal leishmaniasis

Leishmania V. braziliensis infection in asymptomatic domestic animals within an endemic region in the Northeast of Brazil

Background:

American cutaneous leishmaniasis is a commonly neglected, vector-borne tropical parasitic disease that is a major public health concern in Brazil. Leishmania (Viannia) braziliensis is the main species associated with the disease. Accurate diagnosis is based on epidemiological surveillance, clinical assessment, and laboratory testing. Leishmania (V.) braziliensis has been detected in several wild and synanthropic mammals. Their epidemiological role has not been entirely elucidated. This study aimed to assess potential L. braziliensis infections in asymptomatic domestic animals, by molecular and serological testing in endemic areas, in the metropolitan region of Recife.

Methods:

Blood samples and conjunctival fluids were collected from 232 animals (canids, felids, equines, and caprines) for the detection of L. braziliensis using molecular tests (conventional and real-time polymerase chain reaction [PCR and qPCR]). For immunological detection, blood samples from 115 dogs were assessed using enzyme-linked immunosorbent assay.

Results:

Real-time quantitative PCR showed positive results for blood and conjunctival samples in all investigated species. The results of the blood and conjunctival samples were 68.2% and 26.9% in Canis familiaris, 100% and 41.7% in Felis catus, 77.3% and 30.8% in Equus caballus/Equus asinus, and 50% and 33.3% in Capra hircus samples, respectively.

Conclusions:

Results from this study adds valuable information to our understanding of the role of asymptomatic domestic animals, L. braziliensis life cycle, and American cutaneous leishmaniasis in Northeast Brazil.

Overcoming the Negligence in Laboratory Diagnosis of Mucosal Leishmaniasis

The northern region of Brazil, which has the largest number of cases of tegumentary leishmaniasis (TL) in the country, is also the region that has the highest diversity of species of vectors and Leishmania parasites. In this region, cases of mucosal leishmaniasis (ML), a clinical form of TL, exceed the national average of cases, reaching up to 12% of the total annual TL notifications. ML is associated with multiple factors, such as the parasite species and the viral endosymbiont Leishmania RNA virus 1 (LRV1). Being a chronic parasitological disease, laboratory diagnosis of ML poses a challenge for health services. Here, we evaluated more than 700 clinical samples from patients with clinical suspicion of TL, including patients with cutaneous leishmaniasis (CL) and mucosal leishmaniasis, comparing the results of parasitological tests—direct parasitological examination by microscopy (DP) and conventional PCR (cPCR) targeting of both kDNA and hsp70. The DP was performed by collecting material from lesions through biopsies (mucosal lesions) or scarification (cutaneous lesions); for PCR, a cervical brush was used for sample collection. Blood samples were tested employing standardized real-time PCR (qPCR) protocol targeting the HSP70 gene. PCR tests showed higher sensitivity than DP for both CL and ML samples. Considering ML samples only (N = 89), DP showed a sensitivity of 49.4% (N = 44) against 98.8% (N = 88) for kDNA PCR. The qPCR hsp70 for blood samples from patients with ML (N = 14) resulted in superior sensitivity (50%; N = 7) compared to DP (21.4%; N = 3) for samples from the same patients. Our results reinforced the need to implement a molecular test for the diagnosis of ML, in addition to proposing methods less invasive for collecting material from TL patients. Sample collection using a cervical brush in lesions observed in CL and ML patients is easy to perform and less invasive, compared to scarification and biopsies. Blood samples could be a good source for qPCR diagnosis for ML patients. Thus, we propose here a standardized method for collection and for performing of molecular diagnosis of clinical samples from suspicious ML patients that can be applied in reference services for improving ML diagnosis.

Molecular Diagnosis of Leishmaniasis: Quantification of Parasite Load by a Real-Time PCR Assay with High Sensitivity

Real-time PCR was developed to quantify Leishmania infantum kinetoplast DNA and optimized to achieve a sensitivity of 1 parasite/mL. For this purpose, we cloned the conserved kDNA fragment of 120 bp into competent cells and correlated them with serial dilutions of DNA extracted from reference parasite cultures calculating that a parasite cell contains approximately 36 molecules of kDNA. This assay was applied to estimate parasite load in clinical samples from visceral, cutaneous leishmaniasis patients and infected dogs and cats comparing with conventional diagnosis. The study aimed to propose a real-time PCR for the detection of Leishmania DNA from clinical samples trying to solve the diagnostic problems due to the low sensitivity of microscopic examination or the low predictive values of serology and resolve problems related to in vitro culture. The quantitative PCR assay in this study allowed detection of Leishmania DNA and quantification of considerably low parasite loads in samples that had been diagnosed negative by conventional techniques. In conclusion, this quantitative PCR can be used for the diagnosis of both human, canine and feline Leishmaniasis with high sensitivity and specificity, but also for evaluating treatment and the endpoint determination of leishmaniasis.

One Health Approach to Leishmaniases: Understanding the Disease Dynamics through Diagnostic Tools

Leishmaniases are zoonotic vector-borne diseases caused by protozoan parasites of the genus Leishmania that affect millions of people around the globe. There are various clinical manifestations, ranging from self-healing cutaneous lesions to potentially fatal visceral leishmaniasis, all of which are associated with different Leishmania species. Transmission of these parasites is complex due to the varying ecological relationships between human and/or animal reservoir hosts, parasites, and sand fly vectors. Moreover, vector-borne diseases like leishmaniases are intricately linked to environmental changes and socioeconomic risk factors, advocating the importance of the One Health approach to control these diseases. The development of an accurate, fast, and cost-effective diagnostic tool for leishmaniases is a priority, and the implementation of various control measures such as animal sentinel surveillance systems is needed to better detect, prevent, and respond to the (re-)emergence of leishmaniases.

Cost-effectiveness analysis of Mucosal Leishmaniasis diagnosis with PCR-based vs parasitological tests in Colombia

To estimate the cost-effectiveness of available diagnosis alternatives for Mucosal Leishmaniasis (ML) in Colombian suspected patients. A simulation model of the disease's natural history was built with a decision tree and Markov models. The model´s parameters were identified by systematic review and validated by expert consensus. A bottom-up cost analysis to estimate the costs of diagnostic strategies and treatment per case was performed by reviewing 48 clinical records of patients diagnosed with ML. The diagnostic strategies compared were as follows: 1) no diagnosis; 2) parasite culture, biopsy, indirect immunofluorescence assay (IFA), and Montenegro skin test (MST) combined ; 3) parasite culture, biopsy, and IFA combined; 4) PCR-miniexon; and 5) PCR-kDNA. Three scenarios were modeled in patients with ML clinical suspicion, according to ML prevalence scenarios: high, medium and low. Adjusted sensitivity and specificity parameters of a combination of diagnostic tests were estimated with a discrete event simulation (DES) model. For each alternative, the costs and health outcomes were estimated. The time horizon was life expectancy, considering the average age at diagnosis of 31 years. Incremental cost-effectiveness ratios (ICERs) were calculated per Disability Life Year (DALY) avoided, and deterministic and probabilistic sensitivity analyses were performed. A threshold of willingness to pay (WTP) of three-time gross domestic product per capita (GDPpc) (US$ 15,795) and a discount rate of 3% was considered. The analysis perspective was the third payer (Health System). All costs were reported in American dollars as of 2015. PCR- kDNA was the cost-effective alternative in clinical suspicion levels: low, medium and high with ICERs of US$ 7,909.39, US$ 5,559.33 and US$ 4,458.92 per DALY avoided, respectively. ML diagnostic tests based on PCR are cost-effective strategies, regardless of the level of clinical suspicion. PCR-kDNA was the most cost-effective strategy in the competitive scenario with the parameters included in the present model.

Microbiological laboratory diagnostics of neglected zoonotic diseases (NZDs)

This review reports on laboratory diagnostic approaches for selected, highly pathogenic neglected zoonotic diseases, i.e. anthrax, bovine tuberculosis, brucellosis, echinococcosis, leishmaniasis, rabies, Taenia solium-associated diseases (neuro-/cysticercosis & taeniasis) and trypanosomiasis. Diagnostic options, including microscopy, culture, matrix-assisted laser-desorption-ionisation time-of-flight mass spectrometry, molecular approaches and serology are introduced. These procedures are critically discussed regarding their diagnostic reliability and state of evaluation. For rare diseases reliable evaluation data are scarce due to the rarity of samples. If bio-safety level 3 is required for cultural growth, but such high standards of laboratory infrastructure are not available, serological and molecular approaches from inactivated sample material might be alternatives. Multiple subsequent testing using various test platforms in a stepwise approach may improve sensitivity and specificity. Cheap and easy to use tests, usually called "rapid diagnostic tests" (RDTs) may impact disease control measures, but should not preclude developing countries from state of the art diagnostics.

Polymerase chain reaction-based method for the identification of Leishmania (Viannia) braziliensis and Leishmania (Viannia) guyanensis in mucosal tissues conserved in paraffin

INTRODUCTION

In the Americas, mucosal leishmaniasis is primarily associated with infection by Leishmania (Viannia) braziliensis. However, Leishmania (Viannia) guyanensis is another important cause of this disease in the Brazilian Amazon. In this study, we aimed at detecting Leishmaniadeoxyribonucleic acid (DNA) within paraffin-embedded fragments of mucosal tissues, and characterizing the infecting parasite species.

METHODS

We evaluated samples collected from 114 patients treated at a reference center in the Brazilian Amazon by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analyses.

RESULTS

Direct examination of biopsy imprints detected parasites in 10 of the 114 samples, while evaluation of hematoxylin and eosin-stained slides detected amastigotes in an additional 17 samples. Meanwhile, 31/114 samples (27.2%) were positive for Leishmania spp. kinetoplast deoxyribonucleic acid (kDNA) by PCR analysis. Of these, 17 (54.8%) yielded amplification of the mini-exon PCR target, thereby allowing for PCR-RFLP-based identification. Six of the samples were identified as L. (V.) braziliensis, while the remaining 11 were identified as L. (V.) guyanensis.

CONCLUSIONS

The results of this study demonstrate the feasibility of applying molecular techniques for the diagnosis of human parasites within paraffin-embedded tissues. Moreover, our findings confirm that L. (V.) guyanensisis a relevant causative agent of mucosal leishmaniasis in the Brazilian Amazon.

Molecular Epidemiological Survey of Cutaneous Leishmaniasis in Two Highly Endemic Metropolises of Iran, Application of FTA Cards for DNA Extraction From Giemsa-Stained Slides

Background:

PCR has been used for confirmation of leishmaniasis in epidemiological studies, but complexity of DNA extraction and PCR approach has confined its routine use in developing countries.

Objectives:

In this study, recent epidemiological situation of cutaneous leishmaniasis (CL) in two hyper-endemic metropolises of Shiraz and Isfahan in Iran was studied using DNA extraction by commercial FTA cards and kinetoplastid DNA (kDNA)-PCR amplification for detection/identification of Leishmania directly from stained skin scraping imprints.

Patients and Methods:

Fifty four and 30 samples were collected from clinically diagnosed CL patients referred to clinical laboratories of leishmaniasis control centers in Isfahan and Shiraz cities, respectively. The samples were examined by direct microscopy and then scrapings of the stained smears were applied to FTA cards and used directly as DNA source in a nested-PCR to amplify kDNA to detect and identify Leishmania species.

Results:

Fifty four of 84 (64.2%) slides obtained from patients had positive results microscopically, while 79/84 (94%) of slides had positive results by FTA card-nested-PCR. PCR and microscopy showed a sensitivity of 96.4% and 64.2% and specificity of 100% and 100%, respectively. Interestingly, Leishmania major as causative agent of zoonotic CL was identified in 100% and 90.7% of CL cases from Isfahan and Shiraz cities, respectively, but L. tropica was detected from only 9.3% of cases from Shiraz city. All cases from central regions of Shiraz were L. tropica and no CL case was found in Isfahan central areas.

Conclusions:

Filter paper-based DNA extraction can facilitate routine use of PCR for diagnosis of CL in research and diagnostic laboratories in Iran and countries with similar conditions. Epidemiologic changes including dominancy of L. major in suburbs of Shiraz and Isfahan metropolises where anthroponotic CL caused by L. tropica had been established, showed necessity of precise studies on CL epidemiology in old urban and newly added districts in the suburbs.

Molecular prevalence and estimated risk of cutaneous leishmaniasis in Libya

BACKGROUND/PURPOSE

Cutanoeus leishmaniasis (CL) is an endemic disease in the Mediterranean area including Libya. The aim of the present study is to detect the prevalent Leishmania species obtained from smeared cutaneous lesions in addition to studying the diverse sociodemographic risk factors of the reported cases from different provinces of Libya.

METHODS

A total of 250 archived microscopic slides from clinically suspected cases of CL attending the leishmaniasis clinic in the Dermatology Department, Tripoli Central Hospital, Tripoli, Libya, were microscopically examined. Leishmania-DNA was amplified using combined polymerase chain reaction (PCR) targeting kinetoplast-DNA (kDNA) and ribosomal internal transcribed spacer 1 (ITS1)-DNA with restriction fragment length polymorphism analysis for direct Leishmania species identification.

RESULTS

Using kDNA and ITS1-PCR, 22.5% and 20% of cases were positive, respectively. Only 14.4% of cases were positive using microscopy. Nominating ITS1-PCR as the reference standard, kDNA-PCR assay was highly sensitive while microscopy was 100% specific but of limited sensitivity (72%) with a substantial agreement and an overall accuracy of 94.4%. Leishmania major and Leishmania tropica were the predominant species reported from the north-western provinces including Tripoli, Zintan, and Gharyan with their related subprovinces; Asabaa, Mizdan, Alkawasem, and Alorban. CL prevailed more among men and residents of rural areas. House wives and students were the most affected professions. Children were the least affected, while the middle-aged were the most affected age group.

CONCLUSION

L. major and L. tropica are the predominant species in the north-western regions of Libya. ITS1-PCR-restriction fragment length polymorphism assay offered a sensitive, specific, and faster diagnostic method especially with negative parasitologic examination.

Polymerase chain reaction-miniexon: a promising diagnostic method for mucocutaneous leishmaniasis

BACKGROUND

Mucocutaneous leishmaniasis is a chronic disease caused mainly by Leishmania species that belong to Viannia subgenus. It affects upper respiratory airways and may lead to deformity, dysphagia, and even death in severe cases. Diagnosis is a challenge because clinical and histopathologic changes are easily confused with other diseases, and conventional methods for parasite identification and culture have a low sensitivity. Molecular methods have been used in the last two decades. In 2007, we published a validation study using internal transcript spacers and kinetoplast DNA as molecular targets with satisfactory results. In this research, we tested miniexon gene as the target.

METHODS

Mucosal tissue samples from 60 Colombian patients with clinical signs of mucocutaneous leishmaniasis were included. A composite reference standard defined 30 cases and 30 controls. Two blind observers performed patient classification and test application independently. Miniexon gene amplification generated: 226-230 bp fragment for subgenus Viannia; 308 bp fragment for L. amazonensis; 340 bp fragment for L. mexicana; and 418 bp fragment for L. infantum-chagasi.

RESULTS

Polymerase chain reaction (PCR) sensitivity for fresh samples was 87.5% (95% confidence interval [CI] 72.2-100), specificity, 95% (95% CI 83.0-100), and positive likelihood ratio was 17.5 (95% CI 2.58-118.93), similar to results obtained with paraffin-embedded samples. Agreement between observers was 96% (kappa = 0.912; 95% CI 0.815-1.000) for both subgenus Viannia and Leishmania.

CONCLUSIONS

We consider PCR-miniexon as a diagnostic method of first choice for mucocutaneous leishmaniasis due to its excellent diagnostic performance and its ability to discriminate between Leishmania and Viannia subgenera as well as between species belonging to Leishmania subgenus.

Accuracy of mucocutaneous leishmaniasis diagnosis using polymerase chain reaction: systematic literature review and meta-analysis

The diagnosis of mucocutaneous leishmaniasis (MCL) is hampered by the absence of a gold standard. An accurate diagnosis is essential because of the high toxicity of the medications for the disease. This study aimed to assess the ability of polymerase chain reaction (PCR) to identify MCL and to compare these results with clinical research recently published by the authors. A systematic literature review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses: the PRISMA Statement was performed using comprehensive search criteria and communication with the authors. A meta-analysis considering the estimates of the univariate and bivariate models was performed. Specificity near 100% was common among the papers. The primary reason for accuracy differences was sensitivity. The meta-analysis, which was only possible for PCR samples of lesion fragments, revealed a sensitivity of 71% [95% confidence interval (CI) = 0.59; 0.81] and a specificity of 93% (95% CI = 0.83; 0.98) in the bivariate model. The search for measures that could increase the sensitivity of PCR should be encouraged. The quality of the collected material and the optimisation of the amplification of genetic material should be prioritised.

A FRET-based real-time PCR assay to identify the main causal agents of New World tegumentary leishmaniasis

In South America, various species of Leishmania are endemic and cause New World tegumentary leishmaniasis (NWTL). The correct identification of these species is critical for adequate clinical management and surveillance activities. We developed a real-time polymerase chain reaction (PCR) assay and evaluated its diagnostic performance using 64 archived parasite isolates and 192 prospectively identified samples collected from individuals with suspected leishmaniasis enrolled at two reference clinics in Lima, Peru. The real-time PCR assay was able to detect a single parasite and provided unambiguous melting peaks for five Leishmania species of the Viannia subgenus that are highly prevalent in South America: L. (V.) braziliensis, L. (V.) panamensis, L. (V.) guyanensis, L. (V.) peruviana and L. (V.) lainsoni. Using kinetoplastid DNA-based PCR as a gold standard, the real-time PCR had sensitivity and specificity values of 92% and 77%, respectively, which were significantly higher than those of conventional tests such as microscopy, culture and the leishmanin skin test (LST). In addition, the real-time PCR identified 147 different clinical samples at the species level, providing an overall agreement of 100% when compared to multilocus sequence typing (MLST) data performed on a subset of these samples. Furthermore, the real-time PCR was three times faster and five times less expensive when compared to PCR - MLST for species identification from clinical specimens. In summary, this new assay represents a cost-effective and reliable alternative for the identification of the main species causing NWTL in South America.

Leishmaniasis is a neglected disease with more than two million new human infections annually worldwide. Tegumentary leishmaniasis, cutaneous and mucocutaneous, is mainly caused by five Leishmania species of the Viannia complex in South America. Different species can cause disease with similar symptoms but have dissimilar prognoses and may need different therapeutic regimens. Identification of Leishmania species traditionally relies on the multilocus enzyme electrophoresis (MLEE) assay, but it can only be applied to culture-positive samples and takes at least six weeks of intense laboratory work. A reliable and rapid assay for species identification can be a valuable tool. Molecular assays are the fastest and most accurate way to identify the etiological agents causing leishmaniasis. This paper describes a novel real-time PCR assay for identification of the five main species that cause tegumentary leishmaniasis in the New World. The assay correctly identified each of these five species of Leishmania directly from clinical samples. Because of its reliability, speed and simplicity, this assay could be used for species identification in routine laboratory diagnosis of leishmaniasis in endemic regions.

Evaluation of the performance of selected in-house and commercially available PCR and real-time PCR assays for the detection of Leishmania DNA in canine clinical samples

Protozoa of the genus Leishmania are the causative agents of leishmaniosis. Although the polymerase chain reaction (PCR) has proved very effective in the detection of Leishmania DNA, a standardized method does not exist. In this study we attempt a comparative evaluation between one real time PCR (Method D), two in-house (Methods A and C), and a commercially available PCR assay (Method B) for the detection of Leishmania DNA, in order to support reliable diagnostic investigation of leishmaniosis. This evaluation was performed in regard to relative specificity and sensitivity, minimum detection limit (MDL), repeatability and reproducibility using cultured isolates and clinical samples. All the methods under study produced the expected result with the positive and negative controls. However with regard to clinical samples, Method C showed a statistically significant higher level of positivity. Relative sensitivity and specificity of Methods A, B and D in comparison to C was calculated respectively at 50.7%, 43%, 40%, and 90.8%, 93.4% and 89.5%. The MDL for Methods A-D was defined respectively at 30.7, 5, 3.7, and 5 promastigotes/ml. Repeatability and reproducibility were excellent in all cases with only the exception of Method A regarding reproducibility with a different brand of PCR reagents. The results that were recorded indicate that evaluation of PCR assays before their application for research and clinical diagnosis can provide useful evidence for their reliable application. Within this context the use of internal amplification controls and the confirmation of the specificity of the amplification product is recommended.

Prevalence of canine leishmaniasis in Beichuan County, Sichuan, China and phylogenetic evidence for an undescribed Leishmania sp. in China based on 7SL RNA

BACKGROUND

Leishmaniasis is a vector-borne disease, which is still endemic in the west and northwest area of China. Canines are the major reservoirs of Leishmania, the etiological agent of human visceral leishmaniasis. Phlebotomus chinensis is the main transmission vector of zoonotic visceral leishmaniasis (ZVL).

METHODS

In this study, rK39 dip-stick, ELISA and PCR methods were used to investigate the prevalence of canine leishmaniasis (CanL) in Beichuan County, Sichuan Province, China.

RESULTS

Among the 86 dogs which were included in the study, 13 dogs were positive using the dip-stick test (15.12%), while 8 dogs were positive using ELISA (9.30%) and 19 dogs were positive for PCR (22.03%). In total, 32 dogs were positive for one or more tests (37.21%). Interestingly, phylogenetic analysis based on the partial 7SL RNA fragment provided evidence that an undescribed Leishmania species, which is clearly a causative agent of CanL and human visceral leishmaniasis, does exist in China. This result is consistent with our previous study.

CONCLUSIONS

Our work confirmed that canine leishmaniasis is still prevalent in Beichuan County. Further control is urgently needed, as canine leishmaniasis is of great public health importance. The phylogenetic analysis based on 7SL RNA segment provides evidence for the existence of an undescribed Leishmania sp. in China.

Identification of Leishmania spp. by molecular amplification and DNA sequencing analysis of a fragment of rRNA internal transcribed spacer 2

Isoenzyme analysis of cultured parasites is the conventional approach for Leishmania species identification. Molecular approaches have the potential to be more sensitive and rapid. We designed PCR generic primers to amplify a segment of the rRNA internal transcribed spacer 2 (ITS2) from multiple Leishmania species. To validate the selected ITS2 fragment, we tested clinical specimens and compared the species results obtained by the molecular approach (PCR followed by DNA sequencing analysis) with those from the parasitologic approach (in vitro culture followed by isoenzyme analysis). Among the 159 patients with clinical specimens positive by both approaches, a total of eight Leishmania species were identified. The species results were concordant for all but two patients: for one patient, the results were Leishmania (Viannia) guyanensis by the molecular approach versus L. (V.) braziliensis by the parasitologic approach; for the other patient, the results were L. (Leishmania) tropica versus L. (L.) major, respectively. ITS2 PCR, followed by sequencing analysis, can be used to detect and discriminate among Leishmania species. The results confirmed our hypothesis that a region of the ITS2 gene can complement the characterization of Leishmania parasites at the species level. The approach we developed can be used as a diagnostic tool in reference laboratories with adequate infrastructure to perform molecular characterization of pathogens.

Mucosal Leishmaniasis caused by Leishmania (Viannia) braziliensis and Leishmania (Viannia) guyanensis in the Brazilian Amazon

Background

Leishmania (Viannia) braziliensis is a parasite recognized as the most important etiologic agent of mucosal leishmaniasis (ML) in the New World. In Amazonia, seven different species of Leishmania, etiologic agents of human Cutaneous Leishmaniasis, have been described. Isolated cases of ML have been described for several different species of Leishmania: L. (V.) panamensis, L. (V.) guyanensis and L. (L.) amazonensis.

Methodology

Leishmania species were characterized by polymerase chain reaction (PCR) of tissues taken from mucosal biopsies of Amazonian patients who were diagnosed with ML and treated at the Tropical Medicine Foundation of Amazonas (FMTAM) in Manaus, Amazonas state, Brazil. Samples were obtained retrospectively from the pathology laboratory and prospectively from patients attending the aforementioned tertiary care unit.

Results

This study reports 46 cases of ML along with their geographical origin, 30 cases caused by L. (V.) braziliensis and 16 cases by L. (V.) guyanensis. This is the first record of ML cases in 16 different municipalities in the state of Amazonas and of simultaneous detection of both species in 4 municipalities of this state. It is also the first record of ML caused by L. (V.) guyanensis in the states of Pará, Acre, and Rondônia and cases of ML caused by L. (V.) braziliensis in the state of Rondônia.

Conclusions/Significance

L. (V.) braziliensis is the predominant species that causes ML in the Amazon region. However, contrary to previous studies, L. (V.) guyanensis is also a significant causative agent of ML within the region. The clinical and epidemiological expression of ML in the Manaus region is similar to the rest of the country, although the majority of ML cases are found south of the Amazon River.

Molecular approaches for a better understanding of the epidemiology and population genetics ofLeishmania

Molecular approaches are being used increasingly for epidemiological studies of visceral and cutaneous leishmaniases. Several molecular markers resolving genetic differences betweenLeishmaniaparasites at species and strain levels have been developed to address key epidemiological and population genetic questions. The current gold standard, multilocus enzyme typing (MLEE), needs cultured parasites and lacks discriminatory power. PCR assays identifying species directly with clinical samples have proven useful in numerous field studies. Multilocus sequence typing (MLST) is potentially the most powerful phylogenetic approach and will, most probably, replace MLEE in the future. Multilocus microsatellite typing (MLMT) is able to discriminate below the zymodeme level and seems to be the best candidate for becoming the gold standard for distinction of strains. Population genetic studies by MLMT revealed geographical and hierarchic population structure inL. tropica, L. majorand theL. donovanicomplex. The existence of hybrids and gene flow betweenLeishmaniapopulations suggests that sexual recombination is more frequent than previously thought. However, typing and analytical tools need to be further improved. Accessible databases should be created and sustained for integrating data obtained by different researchers. This would allow for global analyses and help to avoid biases in analyses due to small sample sizes.

kDNA minicircle signatures of Leishmania (Viannia) braziliensis in oral and nasal mucosa from mucosal leishmaniasis patients

Polymerase chain reaction (PCR) and low-stringency single-specific primer PCR (LSSP-PCR) analyses were used to detect Leishmania (Viannia) braziliensis DNA and investigate kDNA signatures of parasite populations present in oral and nasal mucosa lesions from mucosal leishmaniasis patients. A total of 25 samples from 22 patients were processed by specific PCR/hybridization assays. Parasite DNA was detected in all samples analyzed. The intraspecific polymorphism of the variable region of L. (V.) braziliensis kDNA minicircles was also investigated by LSSP-PCR. Similar kDNA signatures were observed in parasites recovered from nasal and oral mucosa lesions of the same patient. In contrast, genetically divergent profiles were detected in lesions from patients biopsied at different times within a period of 1 year. This is the first work to report genetic typing of L. (V.) braziliensis directly from human oral and nasal mucosal lesions.

Lesion aspirate culture for the diagnosis and isolation of Leishmania spp. from patients with cutaneous leishmaniasis

The detection of Leishmania spp. in skin lesion aspirates, using a puncture technique, was evaluated in 76 patients with cutaneous leishmaniasis (CL) who were referred to a Leishmaniasis Reference Centre in Brazil. CL was defined based on skin lesions suggestive of the disease and on a positive result of the Montenegro skin test or Giemsa-stained imprints of biopsy fragments. The aspirates were cultured using a vacuum tube device containing culture medium and evaluated for the presence of Leishmania spp. The biphasic medium culture was examined once a week for three weeks. Promastigotes were observed in 53/76 (69.7%) cultures. Stained smears from 60 of the 76 patients were evaluated using PCR-RFLP to detect the conserved minicircle region of Leishmania spp. and to classify the parasite. Of these patients, 45 (75%) showed positive results in aspirate culture and 15 presented negative results. The PCR was positive in 80% (53/60) samples. The PCR-RFLP profile was determined in 49 samples, of which 45 (92%) showed a pattern compatible with Leishmania (Viannia) braziliensis. The aspirate culture is a sensitive and feasible method for diagnosing CL and may be routinely adopted by health services for L. (V.) braziliensis isolation and identification.

Detection of Leishmania kDNA in human serum samples for the diagnosis of visceral leishmaniasis

The performance of PCR to detect Leishmania kDNA in serum for the diagnosis of visceral leishmaniasis (VL) was assessed in serum samples from 65 patients with VL, 17 non-infected individuals and 17 patients with other febrile hepatosplenic diseases. Serum PCR showed a sensitivity of 85%, specificity of 100% and efficiency of 90%. The sensitivity values obtained for blood PCR (97%) and rK39 ELISA (95%) were significantly higher (P=0.01) than the values observed for L. chagasi ELISA (88%) and serum PCR (85%), whilst no difference was observed among the specificity rates obtained with rK39 ELISA (94%; P=0.47) and L. chagasi ELISA (85%; P=0.06). This work suggests that the use of serum samples may be an alternative for the diagnosis of VL when peripheral blood samples are not available or require significant operational efforts.

Molecular diagnosis of Old World cutaneous leishmaniasis and species identification by use of a reverse line blot hybridization assay

Reverse line blot hybridization assays (RLB) have been used for the rapid diagnosis and genotyping of many pathogens. The leishmaniases are caused by a large number of species, and rapid, accurate parasite characterization is important in deciding on appropriate therapy. Fourteen oligonucleotide probes, 2 genus specific and 12 species specific (2 specific for Leishmania major, 3 for L. tropica, 1 for L. infantum, 3 for L. donovani, and 3 for L. aethiopica), were prepared by using DNA sequences in the internal transcribed spacer 1 (ITS1) region of the rRNA genes. Probe specificity was evaluated by amplifying DNA from 21 reference strains using biotinylated ITS1 PCR primers and the RLB. The genus-specific probes, PP and PP3', recognized all Leishmania species examined, while the species-specific probes were able to distinguish between all the Old World Leishmania species. Titrations using purified parasite DNA showed that the RLB is 10- to 100-fold more sensitive than ITS1 PCR and can detect <0.1 pg DNA. The RLB was compared to kinetoplast DNA (kDNA) and ITS1 PCR by using 67 samples from suspected cutaneous leishmaniasis (CL) patients in Israel and the West Bank. The RLB accurately identified 58/59 confirmed positive samples as CL, a result similar to that found by kDNA PCR (59/59) and better than that by ITS1 PCR (50/59). The positive predictive value and negative predictive value of the RLB were 95.1% and 83.3%, respectively. L. major or L. tropica was identified by the RLB in 55 of the confirmed positive cases, a level of accuracy better than that of ITS1 PCR with restriction fragment length polymorphism (42/59). Thus, RLB can be used to diagnose and characterize Old World CL.

Biologia molecular aplicada às dermatoses tropicais

São apresentados conceitos básicos sobre célula, código genético e síntese protéica, e sobre algumas técnicas de biologia molecular, tais como PCR, PCR-RFLP, seqüenciamento de DNA, RT-PCR e immunoblotting. São fornecidos protocolos de extração de nucleotídeos e de proteínas, como salting out no sangue periférico e métodos do fenol-clorofórmio e do trizol em tecidos. Seguem-se exemplos comentados da aplicação de técnicas de biologia molecular para o diagnóstico etiológico e pesquisa em dermatoses tropicais, com ênfase na leishmaniose tegumentar americana e hanseníase.

Polymerase chain reaction with two molecular targets in mucosal leishmaniasis' diagnosis: a validation study

We validated the polymerase chain reaction (PCR) with a composite reference standard in 61 patients clinically suspected of having mucosal leishmaniasis, 36 of which were cases and 25 were non-cases according to this reference standard. Patient classification and test application were carried out independently by two blind observers. One pair of primers was used to amplify a fragment of 120 bp in the conserved region of kDNA and another pair was used to amplify the internal transcript spacers (ITS) rDNA. PCR showed 68.6% (95% CI 59.2-72.6) sensitivity and 92% (95% CI 78.9-97.7) specificity; positive likelihood ratio: 8.6 (95% CI 2.8-31.3) and negative likelihood ratio: 0.3 (95% CI 0.3-0.5), when kDNA molecular target was amplified. The test performed better on sensitivity using this target compared to the ITS rDNA molecular target which showed 40% (95% CI 31.5-42.3) sensitivity and 96% (95% CI 84.1-99.3) specificity; positive likelihood ratio: 10 (95% CI 2.0-58.8) and negative likelihood ratio: 0.6 (95% CI 0.6-0.8). The inter-observer agreement was excellent for both tests. Based upon results obtained and due to low performance of conventional methods for diagnosing mucosal leishmaniasis, we consider PCR with kDNA as molecular target is a useful diagnostic test and the ITS rDNA molecular target is useful when the aim is to identify species.

Oral leishmaniasis: a clinicopathological study of 11 cases

Leishmaniasis is a parasitic disease with diverse clinical manifestations, and considered a public health problem in endemic countries such as Brazil. Mucosal lesions usually involve the upper respiratory tract, with a predilection for nose and larynx. Oral involvement is unusual and in most cases it becomes evident after several years of resolution of the original cutaneous lesions. Oral lesions classically appear as mucosal ulcerations, mainly in the hard or soft palate. This report describes the clinicopathological data of 11 cases of mucocutaneous leishmaniasis with oral manifestations. Two cases of Leishmania (Viannia) braziliensis and one case of Leishmania (Leishmania) amazonensis were confirmed by polymerase chain reaction-restriction fragment length polymorphism or DNA sequencing in mucosal samples.

Comparison of PCR assays for diagnosis of cutaneous leishmaniasis

Three PCR assays for diagnosing leishmaniasis were compared and validated against parasite cultures and microscopic evaluation of stained tissue smears using 92 specimens from suspected cases of cutaneous leishmaniasis (CL) in Israel and the West Bank. Samples from imported and locally acquired disease were examined. The kinetoplast DNA (kDNA) PCR showed the highest sensitivity (98.7%) of any assay, correctly diagnosing 77/78 of the confirmed positive samples, followed by the rRNA gene internal transcribed spacer 1 (ITS1) PCR (71/78 positive, 91.0% sensitivity) and then the spliced leader mini-exon PCR (42/78 positive, 53.8% sensitivity). Either parasite culture or microscopy alone detected 62.8% (49/78) or 74.4% (58/78) of the positive specimens, respectively, while culture and microscopy together improved overall sensitivity to 83.3% (65/78). Except for the kDNA PCR that had six false positives, all other assays were 100% specific. Further, restriction enzyme analysis of the ITS1 PCR product enabled identification of 74.6% of the positive samples, which included strains of Leishmania major (50.9%), Leishmania tropica (47.2%), and the Leishmania braziliensis complex (1.9%). This suggests that a PCR using kDNA should be used for the diagnosis of CL and that an ITS1 PCR can be reliably used for the diagnosis of CL when rapid species identification is needed.

Single-step duplex kDNA-PCR for detection of Leishmania donovani complex in human peripheral blood samples

A duplex polymerase chain reaction (PCR) assay was performed using a sense Leishmania genus-specific oligonucleotides to amplify the conserved region of 120 bp of minicircle kDNA and an additional antisense Leishmania donovani oligonucleotide that amplifies a complex-specific fragment of 90 bp. All 12 tested reference isolates of the L. donovani complex yielded a complex-specific amplification product of 90 bp concurrently with a genus-specific 120-bp product. All 17 tested reference isolates pertaining to other complexes presented only the genus-specific 120-bp product. Peripheral blood samples of twenty patients with visceral leishmaniasis positive by the genus-specific PCR presented both fragments with the duplex assay. This duplex PCR can be applied as a 1-step diagnostic tool where discrimination of L. donovani complex species is relevant for clinical and epidemiologic purposes.

Use of PCR-restriction fragment length polymorphism analysis to identify the main new world Leishmania species and analyze their taxonomic properties and polymorphism by application of the assay to clinical samples

At least 13 characterized Leishmania species are known to infect humans in South America. Five of these parasites are transmitted in the sylvatic ecotopes of the whole French Guianan territory and responsible for cutaneous leishmaniasis. For the diagnosis of cutaneous leishmaniasis, restriction fragment length polymorphism (RFLP) analyses have shown promising results. Thus, the end of the small subunit and internal transcribed spacer 1 of the rRNA genes were sequenced and targeted by PCR-RFLP analysis in the 10 main New World (NW) Leishmania species from the two subgenera. Then, the procedure was tested on 40 samples from patients with cutaneous leishmaniasis, and its results were compared with those of conventional methods. (i) The results of this simple genus-specific method were in agreement with those of previous isoenzyme analyses. (ii) This method distinguished the most medically relevant Leishmania species with only one enzyme (RsaI). (iii) This method could be performed directly on human biopsy specimens (sensitivity of 85.7%). Performing NW Leishmania species typing rapidly and easily in the field constitutes a very valuable improvement for detection of Leishmania spp. Revealing great diversity with several enzymes, this method could also be useful for taxonomic, ecological, and epidemiological studies in space and time.

Response to Silva et al.: Usefulness of PCR-based methods for screening Leishmania in epidemiological studies

The detection of Leishmania in naturally infected rodents in endemic areas is of fundamental importance for defining these rodents as possible reservoir hosts of infection. The use of polymerase chain reaction in conjunction with molecular hybridization has provided important results that could lead to a better understanding of the natural history of leishmaniasis.