Chemosusceptibility analysis of Plasmodium falciparum imported from Comoros to Marseilles, France in 2001-2003

OBJECTIVES: The aim of this work was to study the chemosensitivity of Plasmodium falciparum strains isolated from patients presenting with malaria after having returned from Comoros Islands in 2002-2003, and hospitalized at the North University Hospital, in Marseilles, France. MATERIALS AND METHODS: In vitro drug susceptibility (for strains maintained in culture) and mutation-specific polymerase chain reaction (PCR) assays (for all strains) were performed. RESULTS: Out of 23 strains kept in culture, 50% were shown to be resistant in vitro to chloroquine, 50% were resistant to pyrimethamine, 40% to cycloguanil, 25% to atovaquone, and 7% to mefloquine. However all these strains were susceptible to quinine, halofantrine, and artemether. Moreover, 48 strains were tested by molecular methods. As a result, 69% were shown to have the Asp108 mutation in the dihydrofolate reductase gene (Pfdhfr), the basic mutation associated with antifolate resistance, and 54% had additional mutations Ile51 plus Arg59, associated with a high level of resistance. Furthermore, 90% of the 20 strains tested in 2003 were shown to have the point mutation Pfcrt76 in the P. falciparum chloroquine resistance transporter (Pfcrt) gene recently proposed as a molecular marker of chloroquine-resistance. CONCLUSION: Obtaining plasmodium strains from Comoros to be tested in Marseilles, where all laboratory facilities are available, is a unique opportunity to establish a surveillance of falciparum drug resistance in the Comoros islands.