In vitro susceptibility of plasmodium falciparum isolates to chloroquine and other antimalarial drugs in Ghana

Abstract

The ill vitro susceptibilities of Plasmodium falciparum to chloroquine, Mefloquine and quinine were investigated in three distinct Eco epidemiological zones in Ghana using a modification or the World Health Organisation (WHO) micro-test technique. In vitro drug-sensitivity-tests were based on the movement of the effect of the drugs on the growth and development or malaria parasites. Parasites were cultured in the presence of a range of concentration of antimalaria drugs for one life cycle or part thereof. Sensitivity was then assessed by measuring the quantity of" radiolabelled hypoxantine incorporated into the Parasites in drug Containing wells compared to drugfree wells. The concentrations of the various drugs achieving 50% inhibition were determined. Of the 64 P falciparum isolates tested, overall chloroquine resistance of 37.5% was observed. Though all the isolates were fully sensitive to mefloquine and quinine. four showed reduced sensitivity to quinine. The overall mean IC50 determined for these antimalarial drugs were 1.1 x 10-6 (mol/litre. 1.02 x 10·6mol litre and 2.3 x l0·6mol/ litre for chloroquine, mefloquine and quinine respectively. Findings from this study indicate increasing; levels or P falciparum resistance to chloroquine compared to levels that were seen about a decade ago in the country.