An in vitro micromethod for drug sensitivity testing of Leishmania.

We describe an in vitro microtest which is quantitative, rapid, and readily applicable to parasites isolated from all major forms of human leishmaniasis. It is based on drug-mediated inhibition of promastigote catabolism of a battery of simple 14C-substrates to 14CO2. Each test requires less than 1 microCi. The test is conducted in a serum-free, chemically defined medium containing 120 micrograms protein/ml, minimizing the possible interference of drug: serum protein interaction. Prior adaptation is not necessary to cultivate "difficult-to-grow" species. Leishmania sensitivity to pentavalent antimonials is detectable at micrograms levels below concentrations achievable in patients' sera.