부산대학교 도서관

ABSTRACTResistance to antimalarial drugs is a public health problem worldwide. Molecular markers for drug-resistant malaria, such as pfcrtand pfmdr1polymorphisms, could serve as useful surveillance tools. To evaluate this possibility, sequence polymorphisms in pfcrt(position 76) and pfmdr1(positions 86, 184, 1034, 1042, and 1246) and in vitro drug sensitivities were measured for 65 Plasmodium falciparumisolates from Thailand, Myanmar, Vietnam, and Bangladesh. The pfcrtThr76 polymorphism was present in 97% of samples, consistent with observations that chloroquine resistance is well established in this region. Polymorphisms in pfmdr1clustered into four specific patterns: the wild type (category I), a Tyr86 polymorphism only (category II), a Phe184 polymorphism only (category III), and Phe184 in combination with Cys1034 and/or Asp1042 (category IV). Isolates in categories I and III were more sensitive to chloroquine and more resistant to mefloquine, artesunate, and artemisinin than isolates in categories II and IV (P≤ 0.01). Mefloquine resistance was significantly more common in category I and III isolates than in category II and IV isolates, with a prevalence ratio of 14.95 (95% confidence interval, 3.88 to 57.56). These categories identified mefloquine resistance with a sensitivity and a specificity of 94 and 91%, respectively. The pfmdr1gene copy number was measured by real-time PCR as a ratio of the amount of pfmdr1DNA to the amount of lactate dehydrogenase (ldh) DNA. Eight samples had pfmdr1DNA/ldhDNA ratios ≥3. The isolates in all 8 samples fell into categories I and III and were significantly more resistant to mefloquine, quinine, artemisinin, and artesunate and more sensitive to chloroquine than the isolates in the 57 samples with <3 copies of the gene (P≤ 0.001). Thus, measurement of pfmdr1mutations and gene copy number may be useful for surveillance of mefloquine-resistant malaria in Southeast Asia.