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.


CONCLUSIONS
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.
Mbugi
Erasto V
EV
Department of Veterinary Physiology, Biochemistry, Pharmacology and Toxicology, Faculty of Veterinary Medicine, Sokoine University of Agriculture (SUA), Morogoro, Tanzania. rerasto@yahoo.com
Mutayoba
Benezeth M
BM
Malisa
Allen L
AL
Balthazary
Sakurani T
ST
Nyambo
Thomas B
TB
Mshinda
Hassan
H
D000818:Animals; D000962:Antimalarials / Q000494:pharmacology* / Q000627:therapeutic use; D002675:Child, Preschool; D004094:Dihydropteroate Synthase / Q000235:genetics*; D004338:Drug Combinations; D004351:Drug Resistance / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology; D008297:Male; D021261:Parasitic Sensitivity Tests; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000201:enzymology; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011739:Pyrimethamine / Q000494:pharmacology* / Q000627:therapeutic use; D013413:Sulfadoxine / Q000494:pharmacology* / Q000627:therapeutic use; D013636:Tanzania / Q000453:epidemiology; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*
D000962:Antimalarials; D004338:Drug Combinations; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D011739:Pyrimethamine