棘阿米巴角膜炎致病虫株的超微结构观察

Ultrastructure study of pathogen of acanthamoeba keratitis

目的探讨氯己定（洗必泰）对棘阿米巴角膜炎患者角膜内分离培养虫株的作用，为临床治疗棘阿米巴角膜炎提供实验室依据。方法实验研究。利用扫描电镜观察分离培养虫株的形态特征以及0．02％氯己定作用后的结构变化；利用透射电镜观察角膜病变组织内棘阿米巴的超微结构特征。结果体外培养的棘阿米巴滋养体大小约15～45μm呈圆形、椭圆形、不规则形状，虫体体表粗糙，有棘状胞质突起，以二分裂方式繁殖。包囊大小约10～25μm，球形，表面见皱襞、壁孔及圆形孔盖。棘阿米巴自壁孔处逸出转变成滋养体，脱囊后遗留空囊。经0．02％氯己定作用24h后的滋养体和包囊结构被破坏，虫体崩解成残膜碎片或凝块、颗粒状。经过抗棘阿米巴治疗后的角膜病变组织内未见滋养体，仅见包囊。包囊内外壁结构基本保留，但细胞质蛋白凝固，亚细胞结构退变缺失，包囊处于变性失活状态。结论0．02％氯己定在体外可杀灭棘阿米巴滋养体和包囊，在组织内可杀灭棘阿米巴滋养体，致包囊变性失活。变性失活的棘阿米巴包囊仍可较长时间存留在角膜组织中，并可引发免疫病理性炎性反应，临床治疗中应引起注意。

Objective To observe the ultrastructure of the strains of acanthamoeba isolated from acanthamoeba keratitis （AK）, the morphologic changes of acanthamoeba after culture with 0. 02% chlorhexidine, and uhrastructure characteristics of acanthamoeba in corneal tissue of AK. Methods It was a experimental study. The uhrastructure of acanthamoeba strains cultured with 0.02% chlorhexidine was observed with scanning electron microscope （SEM）. The excited cornea tissues from AK were observed with transmission electron microscope （TEM）. Results Cultured acanthamoeba trophozoites were approximately 15-45 μm in diameter, appeared irregularly round or oval in shape, with rough surface and intrusion of cytoplasm. The trophozoite propagated by ways of binary division. The acanthamoeba cysts were approximately 10-25 μm in diameter, round in shape and with a plica-like surface. The acanthamoeba could change from trophozoite to cyst. The amoeba emerging through ostioles could turn into trophozoite and left an empty cyst. After cultured with 0.02% chlorhexidine for 24 hours, the trophozoite and cyst collapsed and distorted. However, after clinical treatment with 0. 02% chlorhexidine, only the cysts could be seen in corneal tissue of AK. Ectro-and endo-cystic walls were preserved, but the cytoplasma was aggregated and the sub-cytoarchitectures were degenerated or disappeared. Discussion Chlorhexidine at a concentration of 0.02% kills acanthamoeba trophozoites and cysts in vitro. Chlorhexidine （0. 02% ） also kills trophozoites and inhibits the activity of cysts in corneal tissues. However, it should be noticed that the inactive cysts can stay in the cornea for a long time and may cause an immuno-pathologic inflammation of the cornea.