Response of drug resistant isolates of Schistosoma mansoni to antischistosomal agents

Abstract

The susceptibility of four isolates of Schistosoma mansoni (BH, MAP, MPR-1 and K) to four multiple doses of anti-schistosomal agents (hycanthone, niridazole, oxamniquine, and praziquantel) were evaluated in infected female Swiss albino mice. These schistosomal isolates had been maintained in the laboratory without further drug pressure for 20 to 30 generations. Multiple dosage regimens were used for each drug against each isolate of S. mansoni to generate ED50 (effective dose 50%) values. Results demonstrated that the K isolate is resistant to niridazole, the MPR-1 isolate to oxamniquine, and the MAP isolate to both hycanthone and oxamniquine. The BH isolate was susceptible to all drugs and was used as the reference isolate. All isolates were susceptible to parziquantel. 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 demonstrate that the resistance of these isolates are stable over long periods of time without exposure to drugs.

Altered Response of Strain of Schistosoma mansoni to Oxamniquine and Praziquantel

“…This value was 34 mg/kg greater than that found by Drescher et al (1993) for the BH strain (Belo Horizonte, Brazil) but was closer to the value of 62 mg/kg obtained for the K strain (Kenya). Both strains are considered sensitive to OXA.…”

“…In the case of the Brazilian strains the efficacy is generally more than 95% and other parameters show a high susceptibility to these schistosomicides (Dias et al 1982, 1988, Drescher et al 1993. Recently, Araújo et al (1996) studied ten isolates of S. mansoni derived from patients in an endemic area in Bahia, Brazil.…”

“…Drescher et al (1993) worked with the strains BH, K, MAP and MPR-1, previously mentioned and obtained an ED 50 of 42, 36, 13 e 46 mg/kg/5 days, respectively, by oral route. Araújo et al (1996) worked with single doses of PZQ obtained in ED 50 that varied between 92 mg/kg and 640 mg/kg.…”

“…The oogram was considered altered when one of the five maturity degrees, based on the embryo size and morphology, was absent; (d) effective doses (ED) -dose response curves were generated where response was plotted as % efficacy on the y-axis against dose (total mg/kg) on the xaxis. The values of ED were obtained by observing the dose with intersected the curve dose (Drescher et al 1993).…”

Effect of praziquantel on adult Echinostoma paraensei worms in experimentally infected mice

“…The use of PZQ in experimental infection by E. caproni showed efficacy on adult worms (Keiser et al 2006). However, it has been demonstrated that the Schistosoma mansoni trematode strains circulating in Brazil and Africa are susceptible to different doses of praziquantel (Fallon et al 1997;Drescher et al 1993). The efficacy of a combined product containing praziquantel and other drugs has been determined against nematodes (Taweethavonsawat et al 2010) and trematodes (Xiao et al 2011a), which, in the latter, the antihelminthic properties of praziquantel in hamster was better understood (Xiao et al 2011a).…”