Population structure of recrudescent Plasmodium falciparum isolates from Western Uganda

A field study on in vivo drug resistance against chloroquine sulphadoxine/pyrimethamine (S/P) and cotrimoxazole in West Uganda is presented. Polymorphic regions of the genes coding for the merozoite surface protein 1 (MSP1) and MSP2 and of the glutamate rich protein (GLURP) gene were used as markers for genotyping of field populations of Plasmodium falciparum. A total of 549 patients aged 6 months to 80 years were investigated with regard to chloroquine (n = 263) S/P (n = 127) and cotrimoxazole (n = 159). Thick blood films were prepared from a fingerprick for genotyping. Results showed that 59 of 81 P. falciparum samples (72.8%) isolated at day 0 revealed multiclonal infection with 2-7 different bands for any allelic families. The plasmodial population within patients consisted of resistant clones in the occurrence of in vivo drug resistance. Among the isolates the presence of the allelic family MAD20 of MSP1 at day 0 was significantly (P = 0.0041; t-test) associated with increased susceptibility to antimalarials especially to chloroquine and S/P. Thus the use of this method in a field study on in vivo drug resistance demonstrates another potential application of genotyping as a tool for epidemiological investigations.