Flow cytometry to evaluate the parasitemia of Plasmodium falciparum.

The resistance of plasmodiums to the current antimalarial agents has spurred the search for new active molecules of vegetal origin or chemical synthesis. The screening of antimalarial molecules "in vitro" was done by simple but tedious techniques such as quantification of parasitemia through optical microscopy or by using radioactive markers. We have developed a new method to evaluate parasitemia by using the ODAM ATC 3000 flow cytometer and biological cell sorter. We selected the ethidium bromide for labelling the nucleic acids of Plasmodium falciparum, and we optimised the method by using a mathematical model: the design of Hadamar. This simple technique presents the advantage of being an objective and rapid count of large number of red cells (10(6) x 10(7)). This method is rapid, reliable, reproducible, devoid of subjectivity and provides more precise results than those of optical microscopy. The good correlation between paraitemia measured by optical microscopy and fluorescence obtained by flow cytometry allows us to recommend this technic for the screening of new antimalarial molecules.