Reduced Impact of Pyrimethamine Drug Pressure on Plasmodium malariae Dihydrofolate Reductase Gene

Abstract

ABSTRACTMolecular investigations performed following the emergence of sulfadoxine-pyrimethamine (SP) resistance inPlasmodium falciparumhave allowed the identification of the dihydrofolate reductase (DHFR) enzyme as the target of pyrimethamine. Although clinical cases ofPlasmodium malariaeare not usually treated with antifolate therapy, incorrect diagnosis and the high frequency of undetected mixed infections has probably exposed non-P. falciparumparasites to antifolate therapy in many areas. In this context, we aimed to assess the worldwide genetic diversity of theP. malariaedhfrgene in 123 samples collected in Africa and Asia, areas with different histories of SP use. Among the 10 polymorphic sites found, we have observed 7 new mutations (K55E, S58R, S59A, F168S, N194S, D207G, and T221A), which led us to describe 6 new DHFR proteins. All isolates from African countries were classified as wild type, while new mutations and haplotypes were recognized as exclusive to Madagascar (except for the double mutations at nucleotides 341 and 342 [S114N] found in one Cambodian isolate). Among these nonsynonymous mutations, two were likely related to pyrimethamine resistance: S58R (corresponding to C59R inP. falciparumand S58R inPlasmodium vivax; observed in one Malagasy sample) and S114N (corresponding to S108N inP. falciparumand S117N inP. vivax; observed in three Cambodian samples).