日本血吸虫吡喹酮耐药虫体筛选及其超微结构观察

目的应用吡喹酮(PZQ)亚治疗剂量对感染小鼠体内日本血吸虫虫体进行药物压力下的耐药虫体筛选,并探讨经筛选后的虫体对PZQ的敏感性及其超微结构变化。方法应用日本血吸虫雄虫PZQ半数有效致死剂量(ED50)为亚治疗剂量,对感染6周后小鼠喂饲给药30d;肝门静脉灌注法收集雄性成虫体外培养,加入不同浓度PZQ连续培养5d,根据虫体活力,评价对PZQ的敏感性,同时用扫描电镜观察虫体超微结构的变化。结果经实验获得日本血吸虫雄虫PZQ的ED50为20.89mg/kg;应用该剂量对感染小鼠体内连续用药30d后,体外培养观察显示虫体对PZQ敏感性显著下降,扫描电镜观察表明皮层及抱雌沟损害较正常虫体明显减轻;筛选后虫体再用治疗剂量PZQ200mg/kg连续给药5d后,体外培养观察显示,虫体在不同浓度PZQ作用下存活率仍达100%,扫描电镜显示体表及抱雌沟损害比单纯用药30d的虫体更轻。结论在持续药物压力下,感染宿主体内的日本血吸虫可能对PZQ产生一定的耐受性。

Selected schistosomes of decreased praziquantel sensitivity and ultrastructural alterations of worms under drug pressure

Objective To select the Schistosoma japonicum of decreased praziquantel（PZQ）sensitivity and observe the ultrastructural alterations of the worms under the drug pressure.Methods The mice infected with S.japonicum 6 weeks after the infection were treated intragastrically with subcurative doses of PZQ for 30 consecutive days.The male adult worms were obtained by perfusion three weeks after the treatment,then these worms were subjected in vitro in the culture with different PZQ concentrations and the co-incubation continued overnight（16h）.Next morning the worms were washed and resuspended in drug-free medium and observed at the subsequent 5 days.At the incubation for 48 h,the ultrastructural alterations of male worms were observed by scanning electron microscopy（SEM）.Results The dose of PZQ required to kill 50% of adult male worms in vivo（i.e.ED50）was estimated to be 20.89 mg/kg,and the mice infected with S.japonicum were treated intragastrically with the subcurative doses for 30 consecutive days.The surviving worms had the lesser sensitivity to PZQ than the original unselected worms in vitro.The damages of ultrastructure in the tegument and gynecophoral canal in the selected-worms were slight compared with those of the control worms from untreated mice by SEM.While the selected-worms were repeatedly treated with 200 mg/kg PZQ for 5 consecutive days,the survived worms subjected in vitro in the culture of different PZQ concentrations were still 100% survived.The damages of ultrastructure in the tegument and gynecophoral canal in the repeated treatment selected-worms were slight compared with those of the worms from the mice after subjecting to drug pressure for 30 days.Conclusion The survived parasites subjected to repeated PZQ treatments in vivo have decreased their sensitivity to PZQ.