Drug resistance to sulphadoxine-pyrimethamine in Plasmodium falciparum malaria in Mlimba, Tanzania

BACKGROUND: Sulphadoxine-pyrimethamine (SP) has been and is currently used for treatment of uncomplicated Plasmodium falciparum malaria in many African countries. Nevertheless, the response of parasites to SP treatment has shown significant variation between individuals. METHODS: The genes for dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) were used as markers, to investigate parasite resistance to SP in 141 children aged less than 5 years. Parasite DNA was extracted by Chelex method from blood samples collected and preserved on filter papers. Subsequently, polymerase chain reaction (PCR) and restriction fragment length polymorphism (PCR-RFLP) were applied to detect the SP resistance-associated point mutations on dhfr and dhps. Commonly reported point mutations at codons 51, 59, 108 and 164 in the dhfr and codons 437, 540 and 581 in the dhps domains were examined. RESULTS: Children infected with parasites harbouring a range of single to quintuple dhfr/dhps mutations were erratically cured with SP. However, the quintuple dhfr/dhps mutant genotypes were mostly associated with treatment failures. High proportion of SP resistance-associated point mutations was detected in this study but the adequate clinical response (89.4%) observed clinically at day 14 of follow up reflects the role of semi-immunity protection and parasite clearance in the population. CONCLUSION: In monitoring drug resistance to SP, concurrent studies on possible confounding factors pertaining to development of resistance in falciparum malaria should be considered. The SP resistance potential detected in this study, cautions on its useful therapeutic life as an interim first-line drug against malaria in Tanzania and other malaria-endemic countries

Polymerase Chain Reaction To Determine Frequency Of Pyrimethamine (Daraprim) - Resistant Plasmodium falciparum In Volta And Greater Accra Regions Of Ghana

Treatment of malaria is being hampered by the emergence of drug resistant strains of malaria parasites. In this study, mutation specific polymerase chain reaction assays using 3\'-mismatched oligonucleotide primers which annealed to the wild or mutated parasites\' gene encoding dihydrofolate reductase-thymidylate synthase (DHFR-TS) were used to survey P. falciparum strains in two southern regions of Ghana (Volta and Greater Accra regions). Mutations were identified directly from blood samples obtained from patients attending out patient departments in hospitals. A DNA amplification product of 337 base pairs was obtained when reaction products were analysed by electrophoresis. Of 162 smear positive samples collected, 13 (8.0%) contained the Asn-108 codon AAC that confers pyrimethamine resistance, 139 (85.8%) samples contained only the wild-type Ser-108 codon AGC. Out of the 13 pyrimethamine resistant cases, 10 were found in samples obtained from the Volta Region while the rest (3) were from Korle-Bu Teaching Hospital in the Greater Accra Region. No PCR product was found in 10 (6.2%) of 162 samples. After second (nested) PCR, only one sample showed amplified product. Contamination was negligible. PCR amplification of the DHFR-TS could be used to determine frequency of pyrimethamine resistant P. falciparum strains in malaria blood.Plasmodium falciparum résistant dans les régions de Volta et de Greater Accra du Ghana. Le traitement du paludisme est en cours d\' être gêné par l\'émergence de souches de parasites de la malaria résistantes au médicament. Dans cette étude les essais de réaction en chaîne par polymérase (RCP) de mutation spécifique utilisant les primers oligonucléotide de 3\'-mal assortis qui recuisait le gène de parasite muté ou naturel le synthase thymidylate-dihydrofolate réductase (STDHFR) encodant étaient utilisés pour enquêter sur les souches de P. falciparum dans deux régions au sud du Ghana (les régions de Volta et de Greater Accra). Les mutations étaient identifiées directement dans les prélèvement de sang obtenus de malades qui visitent les hôpitaux pour les services de consultation externe. Un produit d\'amplification d\'ADN de 337 paire de base était obtenu quand les produits de réactions étaient analysées par électrophorèse. De 162 frottis positifs prélevés, 13 (8.0%) contenait Asn-108 Codon ACC qui confère la résistance pyriméthamine, 139 (85.8%) prélèvements contenait seulement le type-sauvage Ser- 108 Codon AGC. Ghana Journal of Science Vol. 47 2007: pp. 11-1

Antiplasmodial Activity of Extracts of Tridax Procumbens and Phyllanthus Amarus in in Vitro Plasmodium Falciparum Culture Systems

Background: Aqueous extracts of Tridax procumbens (TP) (Compositae) and Phyllanthus amarus (PA) (Euphorbiaceae) are used in traditional medicine in Ghana to treat malaria. Previous studies have demonstrated the anti-trypanosoma, anti-bacterial and anti-HIV effects of TP and PA.Objective: To assess the antiplasmodial activity of extracts of TP and PA.Method: Aqueous extracts of TP and PA were prepared. A portion of each was freeze-dried and the remaining extracted sequentially with ethyl acetate and chloroform. Ethanolic extracts were also prepared. The antiplasmodial activity of the extracts was assessed with the 3H-hypoxanthine assay using chloroquine-resistant (Dd2) Plasmodium falciparum parasites. Chloroquine was used as the reference drug. The modified tetrazolium-based colorimetric assay was also used to evaluate the red blood cell (RBC)-protective/antiplasmodial activities and cytotoxicities of the extracts.Results: Results showed that TP and PA have antiplasmodial activities. The aqueous and ethanolic extracts of PA were the most active, yielding EC50 values of 34.9ìg/ml and 31.2ìg/ml, respectively in the tetrazolium-based assay. The TP and PA produced and IC50 values of 24.8ìg/ml and 11.7ìg/ml, respectively in the hypoxanthine assay. Protection of human RBCs against P. falciparum damage by the extracts highly correlated with their antiplasmodial activities. None of the extracts, within the concentration range (1.9-500ìg/ml) studied produced any overt toxicity to human RBCs.Conclusion: The results indicate that both PA and TP have activities against chloroquine-resistant P. falciparum (Dd2) parasites. The antiplasmodial principles extracted into water and ethanol but not chloroform or ethyl acetate