Acta tropica
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Cultures of insect forms of Trypanosoma congolense stocks and clones with different susceptibilities to trypanocidal drugs in vivo were initiated from bloodstream trypomastigotes harvested from mammalian hosts and maintained axenically in vitro at 27 degrees C. Growth inhibition of procyclic forms of susceptible and drug-resistant T. congolense occurred after incubation for 48 h with 0.1 ng isometamidium chloride ml or 500 ng diminazene aceturate/ml. ⋯ Concentrations of 1 or 10 ng isometamidium chloride/ml had an irreversible effect when the trypanosomes were exposed to the drug for 24 h. Both drugs used in this study thus showed antitrypanosomal activity on T. congolense procyclic forms but it was not possible to distinguish between drug-resistant and susceptible stocks or clones employing the criteria of growth inhibition or death of trypanosomes in culture.