Gene Amplification of the Multidrug Resistance 1 Gene of Plasmodium vivax Isolates from Thailand, Laos, and Myanmar

Plasmodium vivax mdr1 gene amplification, quantified by real-time PCR, was significantly more common on the western Thailand border (6 of 66 samples), where mefloquine pressure has been intense, than elsewhere in southeast Asia (3 of 149; P = 0.02). Five coding mutations in pvmdr1, independent of gene amplification, were also found.