In vitro chloroquine susceptibility and PCR analysis of pfcrt and pfmdr1 polymorphisms in Plasmodium falciparum isolates from Senegal.

Chloroquine resistance has been linked to mutations in the pfcrt and pfmdr1 genes of Plasmodium falciparum. To estimate the prevalence of the pfcrt K76T, pfmdr1 N86Y, and pfmdr1 D1246Y polymorphisms, isolates of P. falciparum from Senegal, West Africa, were analyzed, and the results were compared to in vitro chloroquine susceptibility. By the in vitro DELI test, 31% of these samples were resistant to chloroquine. Polymerase chain reaction-based assays and confirmatory sequencing demonstrated the pfcrt T76, pfmdr1 Y86, and pfmdr1 Y1246 alleles in 79%, 31%, and 2% of the isolates, respectively. All three mutant alleles were present in both in vitro susceptible and resistant isolates. On the basis of these findings, it appears that these molecular markers are not consistently predictive of in vitro chloroquine resistance in Senegal.