Resistance in vivo of Plasmodium falciparum to co-trimoxazole in western Uganda

Safety and efficacy of co-trimoxazole for treatment and prevention of Plasmodium falciparum malaria: a systematic review

INTRODUCTION

Cotrimoxazole (CTX) has been used for half a century. It is inexpensive hence the reason for its almost universal availability and wide clinical spectrum of use. In the last decade, CTX was used for prophylaxis of opportunistic infections in HIV infected people. It also had an impact on the malaria risk in this specific group.

OBJECTIVE

We performed a systematic review to explore the efficacy and safety of CTX used for P.falciparum malaria treatment and prophylaxis.

RESULT

CTX is safe and efficacious against malaria. Up to 75% of the safety concerns relate to skin reactions and this increases in HIV/AIDs patients. In different study areas, in HIV negative individuals, CTX used as malaria treatment cleared 56%-97% of the malaria infections, reduced fever and improved anaemia. CTX prophylaxis reduces the incidence of clinical malaria in HIV-1 infected individuals from 46%-97%. In HIV negative non pregnant participants, CTX prophylaxis had 39.5%-99.5% protective efficacy against clinical malaria. The lowest figures were observed in zones of high sulfadoxine-pyrimethamine resistance. There were no data reported on CTX prophylaxis in HIV negative pregnant women.

CONCLUSION

CTX is safe and still efficacious for the treatment of P.falciparum malaria in non-pregnant adults and children irrespective of HIV status and antifolate resistance profiles. There is need to explore its effect in pregnant women, irrespective of HIV status. CTX prophylaxis in HIV infected individuals protects against malaria and CTX may have a role for malaria prophylaxis in specific HIV negative target groups.

In vitro activity of antifolate and polymorphism in dihydrofolate reductase of Plasmodium falciparum isolates from the Kenyan coast: emergence of parasites with Ile-164-Leu mutation

We have analyzed the activities of the antifolates pyrimethamine (PM), chlorcycloguanil (CCG), WR99210, trimethoprim (TMP), methotrexate (MTX), and trimetrexate (TMX) against Kenyan Plasmodium falciparum isolates adapted in vitro for long-term culture. We have also assessed the relationship between these drug activities and mutations in dihydrofolate reductase (dhfr), a domain of the gene associated with antifolate resistance. As expected, WR99210 was the most potent drug, with a median 50% inhibitory concentration (IC50) of <0.075 nM, followed by TMX, with a median IC50 of 30 nM. The median IC50 of CCG was 37.80 nM, and that of MTX was 83.60 nM. PM and TMP were the least active drugs, with median IC50s of 733.26 nM and 29,656.04 nM, respectively. We analyzed parasite dhfr genotypes by the PCR-enzyme restriction technique. No wild-type dhfr parasite was found. Twenty-four of 33 parasites were triple mutants (mutations at codons 108, 51, and 59), and only 8/33 were double mutants (mutations at codons 108 and 51 or at codons 108 and 59). IC50s were 2.1-fold (PM) and 3.6-fold (TMP) higher in triple than in double mutants, though these differences were not statistically significant. Interestingly, we have identified a parasite harboring a mutation at codon 164 (Ile-164-Leu) in addition to mutations at codons 108, 51, and 59. This quadruple mutant parasite had the highest TMP IC50 and was in the upper 10th percentile against PM and CCG. We confirmed the presence of this mutation by sequencing. Thus, TMX and MTX are potent against P. falciparum, and quadruple mutants are now emerging in Africa.

Feasibility and effectiveness of cotrimoxazole prophylaxis for HIV-1-infected adults attending an HIV/AIDS clinic in Uganda

BACKGROUND

Cotrimoxazole is recommended for prevention of opportunistic infections in symptomatic HIV patients in sub-Saharan Africa.

METHODS

We examined the feasibility and effectiveness of daily cotrimoxazole prophylaxis in a well-established cohort of HIV-infected adults attending clinics in Entebbe, Uganda. We compared mortality and morbidity rates for 12 months before and after the introduction of cotrimoxazole.

RESULTS

Between August 2000 and February 2002, 94% of cohort members were enrolled onto cotrimoxazole prophylaxis. Revisits were scheduled every 4 weeks to replenish pills; patients attended 61% of revisits. The main reasons for nonenrollment and defaulting were lack of transport, being away from home, and sickness. Drug-related adverse events, mainly itching and rash, were seen in 4% of participants. Although bacterial resistance rate to cotrimoxazole was high, the adjusted mortality incidence rate ratio was significantly reduced after the introduction of cotrimoxazole (0.76; 95% confidence interval, 0.60-0.96; P = 0.020). Overall febrile events and morbidity rates were unchanged after the introduction of cotrimoxazole, but the incidence of malaria was reduced (incidence rate ratio, 0.31; 95% confidence interval, 0.13-0.72).

CONCLUSIONS

Cotrimoxazole prophylaxis can be introduced into routine HIV clinic activities and is associated with a reduction in overall mortality and malaria morbidity, even in an area with high bacterial resistance. These results reinforce the need for large-scale provision of cotrimoxazole prophylaxis for all HIV-positive patients in developing countries.

Effect of co-trimoxazole prophylaxis, antiretroviral therapy, and insecticide-treated bednets on the frequency of malaria in HIV-1-infected adults in Uganda: a prospective cohort study

BACKGROUND

HIV-1 and malaria are common infections in Africa, and cause substantial morbidity and mortality. HIV infection has been associated with an increased incidence of malaria, and more severe disease. Our aim was to assess the effect of antiretroviral treatment (ART) on the frequency of clinical malaria in people with HIV, and to measure the additive effects of co-trimoxazole (trimethoprim and sulfamethoxazole) prophylaxis, ART, and insecticide-treated bednets.

METHODS

In 2001, we enrolled 466 HIV-infected individuals aged 18 years or older in Uganda in a prospective cohort study that provided co-trimoxazole prophylaxis to 399 participants after 5 months of no intervention. In 2003, we enrolled 138 survivors from the initial study, and 897 new participants from the same community, to take antiretroviral therapy (ART) in addition to co-trimoxazole prophylaxis. The ART was in most cases a combination of stavudine, lamivudine, and nevirapine or efavirenz. In 2004, we also gave participants insecticide-treated bednets. Households were visited weekly by study staff to record fever, illness, or death in the preceding 7 days. In cases of reported fever in the previous 2 days, we took blood to test for malaria parasites. We compared the frequency of clinical malaria, adjusting for CD4-cell count, age, sex, and season.

FINDINGS

1035 individuals were given co-trimoxazole and ART (median age 38 years, 74% female, and median CD4-cell count 124 cells/microL); 985 of these, plus four new participants, received co-trimoxazole, ART, and bednets. There were 166 cases of clinical malaria in the study. Compared with a baseline malaria incidence of 50.8 episodes per 100 person-years, co-trimoxazole prophylaxis was associated with 9.0 episodes per 100 person-years (adjusted incidence rate ratio [IRR] 0.24, 95% CI 0.15-0.38); ART and co-trimoxazole with 3.5 episodes per 100 person-years (0.08, 0.04-0.17); and co-trimoxazole, ART, and bednets with 2.1 episodes per 100 person-years (0.05, 0.03-0.08). Malaria incidence was significantly lower during ART and co-trimoxazole than during co-trimoxazole alone (IRR 0.36 [95% CI 0.18-0.74], p=0.0056).

INTERPRETATION

A combination of co-trimoxazole, antiretroviral therapy, and insecticide-treated bednets substantially reduced the frequency of malaria in adults with HIV.

Impact of trimethoprim-sulfamethoxazole prophylaxis on falciparum malaria infection and disease

BACKGROUND

Trimethoprim-sulfamethoxazole (TS) prophylaxis is recommended for persons living with human immunodeficiency virus infection and acquired immunodeficiency syndrome in Africa. TS and the antimalarial combination sulfadoxine-pyrimethamine (SP) share mechanisms of action and resistance patterns, and concerns about the impact of TS resistance on SP efficacy have contributed to reluctance to implement TS prophylaxis in Africa.

METHODS

To determine whether TS prophylaxis impairs SP efficacy for treatment of uncomplicated falciparum malaria, we conducted a randomized, controlled, open-label study of TS prophylaxis. Two hundred and forty children 5-15 years old were randomized in a 2 : 1 fashion to receive either thrice-weekly TS for 12 weeks or no prophylaxis and were treated with SP for subsequent episodes of malaria. The incidence of malaria, SP efficacy, and the prevalence of parasite mutations that confer antifolate drug resistance were measured.

RESULTS

TS prophylaxis had a 99.5% protective efficacy against episodes of clinical malaria, with 97% efficacy against infection. Four SP treatment failures occurred in the control group, and none occurred in the TS group. No evidence was seen for selection by TS of antifolate resistance-conferring mutations in parasite dihydrofolate reductase or dihydropteroate synthase during subclinical infections.

CONCLUSIONS

In this setting of low antifolate resistance, TS was highly effective in preventing falciparum malaria infection and disease and did not appear to select for SP-resistant parasites.

Effects of antifolates--co-trimoxazole and pyrimethamine-sulfadoxine--on gametocytes in children with acute, symptomatic, uncomplicated, Plasmodium falciparum malaria

Antimalarial drugs including the antifolate, pyrimethamine-sulfadoxine (PS), can modulate the prevalence and intensities of gametocytaemia following treatment of acute malaria infections. They may also directly influence the transmission and spread of drug insensitivity. Little is known of the effects of co-trimoxazole (Co-T), another antifolate antimalarial, on gametocytes in children with acute malaria infections. We compared the effects of Co-T and PS on the prevalence and intensities of gametocytaemia and gametocyte sex ratios in 102 children aged 0.5-12 years presenting with acute and uncomplicated falciparum malaria. Compared to pre-treatment, both drugs significantly increased gametocyte carriage post-initiation of treatment. However, gametocyte carriage was significantly lower on day 14 in those treated with Co-T than PS. Significant increase in gametocytaemia with time occurred in PS--but not Co-T-treated children. Kaplan-Meier survival curve of the cumulative probability of remaining gametocyte-free in children who were agametocytaemic at enrollment showed that by day 7 of follow up, children treated with PS had a significantly higher propensity to have developed gametocytes than in Co-T-treated children (Log-rank statistic 5.35, df = 1, P = 0.02). Gametocyte sex ratio changes were similar following treatment with both drugs. PS and Co-T treatment of acute malaria infections in children from this endemic area is associated with significant increases in prevalence and intensities of gametocytaemia but these effects are more marked in those treated with PS than Co-T.

Effect of co-trimoxazole prophylaxis on morbidity, mortality, CD4-cell count, and viral load in HIV infection in rural Uganda

BACKGROUND

Prophylaxis with co-trimoxazole (trimethoprim-sulphamethoxazole) is recommended for people with HIV infection or AIDS but is rarely used in Africa. We assessed the effect of such prophylaxis on morbidity, mortality, CD4-cell count, and viral load among people with HIV infection living in rural Uganda, an area with high rates of bacterial resistance to co-trimoxazole.

METHODS

Between April, 2001, and March, 2003, we enrolled, and followed up with weekly home visits, 509 individuals with HIV-1 infection and their 1522 HIV-negative household members. After 5 months of follow-up, HIV-positive participants were offered daily co-trimoxazole prophylaxis (800 mg trimethoprim, 160 mg sulphamethoxazole) and followed up for a further 1.5 years. We assessed rates of malaria, diarrhoea, hospital admission, and death.

FINDINGS

Co-trimoxazole was well tolerated with rare (<2% per person-year) adverse reactions. Even though rates of resistance in diarrhoeal pathogens were high (76%), co-trimoxazole prophylaxis was associated with a 46% reduction in mortality (hazard ratio 0.54 [95% CI 0.35-0.84], p=0.006) and lower rates of malaria (multivariate incidence rate ratio 0.28 [0.19-0.40], p<0.0001), diarrhoea (0.65 [0.53-0.81], p<0.0001), and hospital admission (0.69 [0.48-0.98], p=0.04). The annual rate of decline in CD4-cell count was less during prophylaxis than before (77 vs 203 cells per microL, p<0.0001), and the annual rate of increase in viral load was lower (0.08 vs 0.90 log(10) copies per mL, p=0.01).

INTERPRETATION

Daily co-trimoxazole prophylaxis was associated with reduced morbidity and mortality and had beneficial effects on CD4-cell count and viral load. Co-trimoxazole prophylaxis is a readily available, effective intervention for people with HIV infection in Africa.

Pyrimethamine-sulfadoxine resistance in Plasmodium falciparum: what next?

Chemotherapy remains the only practicable tool to control falciparum malaria in sub-Saharan Africa, where >90% of the world's burden of malaria mortality and morbidity occurs. Resistance is rapidly eroding the efficacy of chloroquine, and the combination pyrimethamine-sulfadoxine is the most commonly chosen alternative. Resistant populations of Plasmodium falciparum were selected extremely rapidly in Southeast Asia and South America. If this happens in sub-Saharan Africa, it will be a public health disaster because no inexpensive alternative is currently available. This article reviews the molecular mechanisms of this resistance and discusses how to extend the therapeutic life of antifolate drugs.

Co-trimoxazole compared with sulfadoxine-pyrimethamine in the treatment of uncomplicated malaria in Kenyan children

Sulfadoxine-pyrimethamine (SP) and co-trimoxazole were both effective in reducing fever, clearing parasitaemia and improving anaemia in children aged < 5 years with uncomplicated malaria in 2 Kenyan endemic sites, Oyugis in the west and Tiwi on the coast. We compared the efficacy of these 2 regimens (in May-July 1998) by evaluating clinical and parasitological responses over 14 days. The combined incidence of parasitological failure for the combined sites for co-trimoxazole was 14/123 (11%) and for SP 23/145 (16%) (RR 0.72, 95% confidence interval [CI] 0.31-1.46, P = 0.289). The 14-day clinical failure rate for the combined sites for co-trimoxazole was 4/123 (3.3%), and for SP 8/145 (5.5%), (RR 1.69, 95% CI 0.91-3.15, P = 0.129). The results indicate that the risk of treatment failure for the 2 regimens was similar. The antimalarial use of co-trimoxazole in uncomplicated malaria needs further investigation, since the 10-12-h elimination half-life of both components should reduce selective pressure for resistance. In addition, use of a 2-day high-dose course, tested previously, requires further study to demonstrate its efficacy.

Correlation of in vivo-resistance to chloroquine and allelic polymorphisms in Plasmodium falciparum isolates from Uganda

The efficacy of chloroquine in the treatment of uncomplicated falciparum malaria in Africa is heavily compromised by high levels of drug resistance. The occurrence of active site mutations in the Plasmodium falciparum multi drug resistance-gene 1 (pfmdr1) has been associated with development of resistance to chloroquine. This study investigates the occurrence of several mutations at codons 86, 1042 and 1246 of the pfmdr1-gene in infected blood samples taken from Ugandan children before treatment with chloroquine and their relationship to clinical and parasitological resistance. Even though a clear association of CQR to one certain pfmdr1 single point mutation could not be substantiated, the frequency of resistance was consistently higher for samples revealing any of the mutations than among wild type samples, and 90% of the clinically resistant samples did present a mutation. Thus detection of these allelic pfmdr1 polymorphisms is not a decisive factor for prediction of clinical chloroquine resistance, but an interplay of the different mutations with unknown cofactors is to be assumed and the possible role of other genetic alterations remains to be investigated.