Association between prevalence of pyrimethamine resistance and double mutation in pfdhfr gene in West Bengal, India

To find whether antifolate drug (pyrimethamine) resistance has occurred in the two malaria endemic zones (Kolkata and Purulia) of West Bengal, India. Parasitic bloods were collected from patients of Kolkata and Purulia, in vitro susceptibility test were performed in those 90 isolates. Now parasitic DNA was isolated by phenol chloroform extraction method and then polymerase chain reaction and restriction fragment length polymorphism analysis of different codons of pfdhfr gene (51, 59, and 108) were assessed in Plasmodium falciparum isolates from patients in India. Among 45 isolates from Kolkata dhfr mutant isolates at codons 108, 51 and 59 were found in 71.11%, 100% and 15.55% isolates respectively while in Purulia mutation found in those codons were 42.22%, 57.77% and 0%, respectively. In Kolkata, the isolate having double mutation (N108 + 51I) were resistant to pyrimethamine (P < 0.01) whereas in Purulia N108 mutation is occurred with both mixed and mutant 51I mutation. Our present findings implicate that due to enormous drug (pyrimethamine) pressure double mutation with dhfr S108N/T and N51I was highly correlated (P < 0.01) with in vitro pyrimethamine resistance in two malaria endemic region of West Bengal. The increase in the number of dhfr mutations was strongly correlated to resistance to pyrimethamine.