Prolonged extracellular development of Plasmodium falciparum and the favoring effect of carnitine

Abstract

Merozoites of Plasmodium falciparum placed in an erythrocyte sonicate medium under appropriate conditions have been found to develop extracellularly through a complete schizogonic cycle. Although 20–30% of the merozoites developed into rings at 14 h, only 1–2% went further to produce trophozoites and schizonts. This proportion was too small to permit extracellular maintenance through additional cycles. A series of 36-h experiments revealed a favoring effect of carnitine and of other modifications in culture medium, including a high level of magnesium. These improvements have permitted extracellular culture through three schizogonic cycles over a 6-day period with an approximately fivefold increase in parasite number at each schizogony at 48 and at 96 h and with infectivity to erythrocytes demonstrated at 144 h.