Influence of the asexual parasite biomass on in vitro susceptibility of Plasmodium falciparum to antimalarial drugs in Abidjan

Abstract

The in vitro activities of artemisinin, dihydroartemisinin (the biologically active metabolite of artemisinin derivatives), chloroquine and pyronaridine were assessed in 32 isolates of Plasmodium falciparum from Abobo in the northern of Abidjan district (Cote dfIvoire) using a test based on the standard microtechnique recommended by the World Health Organization (WHO). The parasites densities were ranged between 8,000 and 540,000 rings/ƒÊl of blood. The geometric means 50% inhibitory concentration (GMIC50) values for chloroquine, pyronaridine and artemisinin were 145.5 nM (95% confidence interval (CI) =65-226 nM), 17.69 nM (95% CI=9.1-26.3 nM) and 5.72 nM (95% CI=2.3-9.1 nM), respectively. Dihydroartemisinin was the most potent drug against chloroquine-sensitive and chloroquine-resistant isolates with a geometric mean of 2.72 nM. There was no correlation between the parasite densities and the responses to chloroquine (r2=0.01, p<0.5), pyronaridine (r2=0.13, p<0.05), artemisinin (r2=0.13, p<0.05) and dihydroartemisinin (r2=0.07, p<0.1).