In vitro development of suramin-resistant clones of Trypanosoma evansi.

By exposure to gradually increasing concentrations of suramin in modified Baltz's cell free culture system, suramin-resistant clones of Trypanosoma evansi, JGcl-160, JX-lcl-160 and ZJcl-140, were derived from suramin-sensitive clones JGcl, JX-lcl and ZJcl, respectively, over a period of 550 days. In vitro tests showed that the IC50 values of JGcl-160, JX-lcl-160 and ZJcl-140 were 358.5, 412.3 and 246.4 micrograms/ml respectively, which were 1792.5, 1874.1 and 1760.0 times higher than those of their parent clones. The values for the curative dose CD100 for intact mice infected with JGcl-160, JX-lcl-160 and ZJcl-140 were 80, 120 and 30 mg/kg respectively, which were 5.3, 8.0 and 3.0 times higher than those of each parent clone. The CD100 values for immunosuppressed mice infected with these clones were 250, 300 and 100 mg/kg, respectively, which were 3.1, 2.5 and 3.3 times higher those for intact mice infected with the same clones.