Baseline in vitro efficacy of ACT component drugs on Plasmodium falciparum clinical isolates from Mali

In vitro susceptibility to antimalarial drugs of Malian Plasmodium falciparum isolates collected between 2004 and 2006 was studied. Susceptibility to chloroquine and to three artemisinin-based combination therapy (ACT) component drugs was assessed as a first, to our knowledge, in vitro susceptibility study in Mali. Overall 96 Malian isolates (51 from around Bamako and 45 collected from French travellers returning from Mali) were cultivated in a CO₂ incubator. Fifty percent inhibitory concentrations (IC₅₀s) were measured by either hypoxanthine incorporation or Plasmodium lactate dehydrogenase (pLDH) ELISA. Although the two sets of data were generated with different methods, the global IC₅₀ distributions showed parallel trends. A good concordance of resistance phenotype with pfcrt 76T mutant genotype was found within the sets of clinical isolates tested. We confirm a high prevalence of P. falciparum in vitro resistance to chloroquine in Mali (60–69%). While some isolates showed IC₅₀s close to the cut-off for resistance to monodesethylamodiaquine, no decreased susceptibility to dihydroartemisinin or lumefantrine was detected. This study provides baseline data for P. falciparum in vitro susceptibility to ACT component drugs in Mali.