In vitro activity of chloroquine, quinine, mefloquine and halofantrine against Gabonese isolates of Plasmodium falciparum

OBJECTIVES To determine the in vitro activity of antimalarial drugs against isolates of Plasmodium falciparum in Gabon. METHODS Plasmodium falciparum isolates were collected from symptomatic infections in the hospitals of Bakoumba and Franceville, south-east Gabon and in 2000. In vitro activity of chloroquine, quinine, mefloquine, halofantrine was measured by the isotopic microtest. RESULTS A total of 60 and 62 isolates gave interpretable data in Franceville and Bakoumba, respectively. In Franceville, 50.0% (mean IC50 = 111.7 nm), 0% (mean IC50 = 156.7 nm), and 21.2% (mean IC50 = 12.4 nm) of isolates, respectively, showed in vitro resistance to chloroquine, quinine and mefloquine. In Bakoumba, we saw resistance to chloroquine, quinine, mefloquine and halofantrine in 95.0% (mean IC50 = 325.8 nm), 10.2% (mean IC50 = 385.5 nm), 47.5% (mean IC50 = 24.5 nm) and 18.2% (mean IC50 = 1.9 nm) of isolates, respectively. Activities of chloroquine and mefloquine, chloroquine and quinine, and mefloquine and quinine were positively correlated. CONCLUSIONS Antimalarial drug resistance is high in this area of Gabon. The extent of resistance is disparate, as all tested drugs were less efficacious in Bakoumba than in Franceville.