Polymorphic patterns of pfcrt and pfmdrl in Plasmodium falciparum isolates along the Thai-Myanmar border

Objective:To investigate the distribution and patterns of pfcrt and pfmdr1 polymorphisms in Plasmodium falciparum(P.falciparum)isolates collected from the malaria endemic area of Thailand along Thai-Myanmar border.Methods:Dried blood spot samples were collected from 172 falciparum malaria patients prior received treatment.The samples were extracted using chelex to obtain parasite DNA.PCR-RFLP was employed to detect pfert mutation at codons 76,220,271,326,3S6 and 371,and the pfmdr1mutation at codon 86.Pfmdr1 gene copy number was determined by SYBR Green 1 real-time PCR.Results:Mutant alleles of pfcrt and wild type allele of pfmdrl were found in almost all samples.Pfmdrl gene copy number in isolates collected from all areas ranged from 1.0 to S.0 copies and proportion of isolates carrying>1 gene copies was 38.1%.The distribution and patterns of pfcrt and pfmdrl mutations were similar in P.falciparum isolates from all areas.However,significant differences in both number of gfmdr1 copies and prevalence of isolates carrying>1 gene copies were observed among isolates collected from different areas.The median pfmdr1 copy number in P.falciparum collected from Kanchanaburi and Mae Hongson were 2.5 and 2.0,respectively and more than half of the isolates carried>1 gene copies.Conclusions:The observation of pfindr1 wild type and increasing of gene copy number may suggest declining of artesunate-mefloquine treatment efficacy in P.falciparum isolates in this border area.