LEISHMANIA RESISTANT TO SODIUM STIBOGLUCONATE - DRUG-ASSOCIATED MACROPHAGE-DEPENDENT KILLING

A total of 17 Leishmania isolates, 6 of them isolated from antimony-re sistant patients, were collected in the Sudan and tested for their sen sitivity to sodium stibo,oluconate (Pentostam) as promastigotes. Six o f those isolates were tested as amastigotes infecting a murine macroph age cell line. The results indicated that the conventional promastigot e screening assay did not correlate with the clinical picture, whereas the amastigote/macrophage system produced results that pertained to t he in vivo responses to the drug. A laboratory-generated resistant str ain of L. major was adapted to grow at a high concentration of Pentost am (1000 mu g/ml) as promastigotes but was quite sensitive to the drug at much lower concentrations in the amastigote/(macrophage system (20 mu g/ml), thus suggesting that Pentostam's inhibitory action is media ted through the macrophage rather than through a direct toxic effect e xerted on the parasite.