Analysis of resistance to pyrimethamine/sulphadoxine of isolates of Plasmodium falciparum from Eastern Thailand.

The in vitro susceptibility of five field isolates of Plasmodium falciparum from the region of the Thai-Kampuchean border to pyrimethamine, sulphadoxine, and their combination, was determined using a microtitre test system and media deficient in p-aminobenzoic acid and folic acid. Two-fold serial dilutions of pyrimethamine ranging from concentrations of 8.0 to 0.