Prevalence of polymorphisms in antifolate drug resistance molecular marker genes pvdhfr and pvdhps in clinical isolates of Plasmodium vivax from Kolkata, India.

Sulfadoxine-pyrimethamine has never been recommended for the treatment of Plasmodium vivax malaria as the parasite is intrinsically resistant to pyrimethamine. The combination was introduced as a promising agent to treat Plasmodium falciparum malaria in many countries but was withdrawn after a few years due to development and spread of resistant strains. Presently, sulfadoxine-pyrimethamine is used as a partner drug of artemisinin-based combination therapy to treat uncomplicated falciparum malaria, and a combination of artesunate-sulfadoxine-pyrimethamine is currently in use in India. In countries like India, where both P. vivax and P. falciparum are equally prevalent, some proportion of P. vivax bacteria is exposed to sulfadoxine-pyrimethamine due to misdiagnosis and mixed infections. As reports on the in vivo therapeutic efficacy of sulfadoxine-pyrimethamine in P. vivax are rare, the study of mutations in the marker genes P. vivax dhfr (pvdhfr) and pvdhps is important for predicting drug selection pressure and sulfadoxine-pyrimethamine resistance monitoring. We studied the prevalence of point mutations and haplotypes of both the genes in 80 P. vivax isolates collected from urban Kolkata, India, by the DNA sequencing method. Point mutation rates in both the genes were low. The double mutant pvdhfr A15N50R58N117I173 (mutations are in boldface) and the single mutant pvdhps genotype S382G383K512A553V585 were more prevalent, while 35% of the isolates harbored the wild-type genotype. The triple mutant ANRNI-SGKAV was found in 29.9% isolates. No quintuple mutant genotype was recorded. The P. vivax parasites in urban Kolkata may still be susceptible to sulfadoxine-pyrimethamine. Hence, a combination of antimalarial drugs like artesunate-sulfadoxine-pyrimethamine introduced for P. falciparum infection might be effective in P. vivax infection also. Study of the therapeutic efficacy of this combination in P. vivax is thus strongly suggested. (The study protocol was registered in the Clinical Trial Registry-India [CTRI] of the Indian Council of Medical Research under registration number CTRI/2011/09/002031.).