RESPONSE OF DRUG-RESISTANT ISOLATES OF SCHISTOSOMA-MANSONI TO ANTISCHISTOSOMAL AGENTS

The susceptibility of four isolates of Schistosoma mansoni (BH, MAP, M PR-1 and K) to four multiple doses of anti-schistosomal agents (hycant hone, niridazole, oxamniquine, and praziquantel) were evaluated in inf ected female Swiss albino mice. These schistosomal isolates had been m aintained in the laboratory without further drug pressure for 2 0 to 3 0 generations. Multiple dosage regimens were used for each drug agains t each isolate of S. mansoni to generate ED50 (effective dose 50%) val ues. Results demonstrated that the K isolate is resistant to niridazol e, the MPR-1 isolate to oxamniquine, and the MAP isolate to both hycan thone and oxamniquine. The BH isolate was susceptible to all drugs and was used as the reference isolate. All isolates were susceptible to p raziquantel. The significance of the difference in response of the MPR -1 and MAP isolates is discussed. These results confirm the resistance of these isolates of S. mansoni to three schistosomicides and demonst rate that the resistance of these isolates are stable over long period s of time without exposure to drugs.