PLASMODIUM-FALCIPARUM - RECRUDESCENCE OF PARASITES IN CULTURE

The basis of recrudescence, the reappearance of malaria parasites afte r chemotherapy or after failure of immune suppressions of the parasite s, was studied in cultures of Plasmodium falciparum. When the cultured parasites were exposed eight rimes over a 4-day period to 5% D-sorbit ol, which destroyed infected RBCs containing trophozoites or schizonts , they showed recrudescence several days after cessation of treatment. Pyrimethamine-sensitive parasites were cleared by 10(-6) M pyrimetham ine; pyrimethamine-resistant parasites also were cleared by 10(-4) M p yrimethamine. Both groups of parasites underwent recrudescence in the same manner as those exposed to 5% D-sorbitol. These recrudescent para sites were found to be as susceptible to these treatments as were the parasites before treatment. Therefore, our results strongly suggest th at a subpopulation of the parasites escapes the effect of drugs by a m echanism other than drug resistance. (C) 1995 Academic Press, Inc.