血吸虫对吡喹酮抗药性的研究Ⅱ 曼氏血吸虫吡喹酮敏感株与抗性株虫卵和毛蚴对吡喹酮的反应性

STUDIES ON RESISTANCE OF SCHISTOSOMA TO PRAZIQUANTEL Ⅱ. RESPONSES OF EGGS AND MIRACIDIA OF PRAZIQUANTEL-RESISTANT AND -SUSCEPTIBLE SCHISTOSOMA MANSONI TO PRAZIQUANTEL

目的 比较曼氏血吸虫吡喹酮敏感株与抗性株虫卵和毛蚴对吡喹酮的反应性 ,旨在运用敏感株与抗性株反应性间的差异 ,建立简单快速吡喹酮敏感性检测方法。方法 将各株虫卵分别孵育于 5× 10 -6、10 -6、5× 10 -7mol/ L和 10 -7mol/ L吡喹酮溶液中 2 4h,后移至清水孵化 ,比较虫卵的孵化率。将各株毛蚴分别暴露于 10 -3 、10 -4 、10 -5、5× 10 -6、10 -6、5× 10 -7mol/ L和 10 -7mol/ L吡喹酮溶液中 ,0、1、5 min后观察比较毛蚴的运动及形态学变化。结果 经 10 -6mol/ L 和 5× 10 -7mol/L吡喹酮孵育 2 4h后 ,敏感株血吸虫虫卵的孵化率分别为 4.2 %和 3 0 .7% ,抗性株分别为 2 4.2 %和61.2 %。当毛蚴暴露于 5× 10 -6mol/ L吡喹酮中 ,敏感株 10 0 %毛蚴体中部立刻收缩变形 ,而抗性株仅见 13 .4%毛蚴变形 ;当暴露于 10 -6mol/ L 吡喹酮 0、1、5 min后 ,敏感株毛蚴的变形率分别为3 5 .5 %、63 .9%、91.2 % ;抗性株分别为 0、7.6%、14 .3 %。结论 曼氏血吸虫吡喹酮抗性株和敏感株虫卵与毛蚴阶段对吡喹酮的体外反应性的差异均非常显著。提示 ,将毛蚴移入 10 -6mol/ L吡喹酮溶液中 1min,镜下观察其变形率 ,作为曼氏血吸虫对吡喹酮敏感性的检测方法 。

Objective To develop a test in vitro to detect the susceptibility of Schistosoma mansoni to praziquantel and monitor for the presence of praziquantel resistance in the field, by comparing the responses of eggs and miracidia of praziquantel resistant and susceptible S. mansoni to praziquantel. Methods Eggs of various isolates of S. mansoni were incubated in 5×10 -6 ,10 -6 ,5×10 -7 and 10 -7 mol/L praziquantel for 24 hours, then the eggs were transferred to fresh water to hatch miracidia and the hatch rates were compared. Miracidia of various isolates of S. mansoni were exposed to 10 -3 ,10 -4 ,10 -5 ,5×10 -6 ,10 -6 ,5×10 -7 and 10 -7 mol/L praziquantel for 0, 1 and 5 min and then the swimming behavior and morphological changes were observed. Results Following the incubation in 10 -6 and 5×10 -7 mol/L praziquantel solutions for 24 h, the hatching rates of the eggs of all susceptible isolates were 4 2% and 30 7% respectively which were significantly lower than those of the all resistant isolates which were 24 2% and 61 2%. One hundred percent of miracidia from the susceptible isolates exposed to 5×10 -6 mol/L praziquantel immediately contracted in the middle part of their bodies, while only 13 4% of miracidia from the resistant isolates immediately changed shape. In 10 -6 and 5×10 -6 mol/L praziquantel the percentages of the susceptible isolates changed shape at 0, 1 and 5 min intervals by 35 5%, 63 9% and 91 2% respectively, which were significantly higher than those of the resistant isolates which changed shape by 0, 7 6% and 14 3%. Conclusion There were significant differences responses to praziquantel at the egg and miracidial stages of S. mansoni between praziquantel susceptible and resistant isolates in vitro. The differences of percentage change in shape of miracidia between resistant and susceptible isolates following exposure to 10 -6 M praziquantel for 1 minute may be used to determine whether failed therapy in patients infected with S. mansoni is due to the presence of praziquantel resistant worms.