Schistosoma mansoni: genetic complementation analysis shows that two independent hycanthone/oxamniquine-resistant strains are mutated in the same gene.

Two drug-resistant strains of Schistosoma mansoni were compared in this study in order to decide whether they are both mutated in the same gene with respect to drug-sensitive schistosomes. One of the two strains was isolated in the laboratory, while the other one originated from a treated uncured patient and was subsequently drug selected in the laboratory. The approach consisted in a genetic complementation test performed essentially by crossing the two strains and assessing resistance in the progeny. Since no reappearance of drug sensitivity was detected in the progeny, it was concluded that the two strains failed to complement and were therefore mutated in the same gene. This finding suggests that a single step of drug activation operates in sensitive schistosomes and is ineffective in resistant worms.