Plasmodium falciparum in Kinshasa, Zaire: in vitro drug susceptibility studies.

In June 1986, Plasmodium falciparum parasites were collected from 33 children presenting at the Mama Yemo Hospital in Kinshasa (Zaire) and were successfully tested in vitro by a 48-hr reinvasion test for their susceptibility to various antimalarial drugs. In vitro resistance to chloroquine was found in 82% of the isolates, a marked increase over findings obtained by the same technique 3 years ago in Kinshasa. In vitro chloroquine resistance was not associated with a history of previous drug intake. The inhibitory endpoints for quinine varied from 0.03 to 1 microM, and correlated with the chloroquine endpoints in the corresponding isolates (r = 0.64). Pyrimethamine resistance in vitro was demonstrated in 52% of the isolates tested.