Sensitivity in vitro of Plasmodium falciparum to three currently used antimalarial drugs on the western border of Thailand

The sensitivity in vitro of Plasmodium falciparum to mefloquine, quinine an d artemisinin was assessed in an area of multi-drug resistance on the Thai- Myanmar border, using the World Health Organization's microtest, based on s chizont maturation inhibition. Participating individuals were exclusively t hose who had contracted their infections within Myanmar. A total of 34 succ essful tests were carried out for mefloquine and quinine, showing a marked decrease in sensitivity compared to previously published results. Ten artem isinin tests were successful, with many failures due to the poor storage st ability of the test plates. The implications of the shelf-life of the artem isinin plates is discussed. These results contribute to setting a base line of sensitivity to artemisinin in vitro.