In vitro confirmation of chloroquine-resistant Plasmodium falciparum malaria in KwaZulu.

In May 1987 and January 1988 the chloroquine sensitivity of Plasmodium falciparum in the Ubombo and Ingwavuma districts of KwaZulu was determined by a modified in vitro microtest in which the patients' plasma was replaced with non-immune human AB serum and the test plates were incubated in an atmosphere of 3% oxygen, 4% carbon dioxide and 93% nitrogen. A success rate of 74% was achieved using this technique. All of 23 successfully tested isolates from malaria patients reporting to clinics and a hospital in these areas were found to be resistant to chloroquine, schizogony being inhibited at 32 pmol per well in the majority of tests. Seventy-five per cent of the isolates obtained through active surveillance in the Ubombo district were found to be resistant in varying degrees. Malarial parasites collected from clinics and a hospital in the endemic area did not change markedly in their in vitro response to chloroquine during the 8-month period May 1987-January 1988.