聚乙二醇促进沙眼衣原体生长最适浓度的探讨及对药物敏感性的影响

Optimization of polyethylene glycol concentrations for the growth of Chlamydia trachomatis and evalu- ation of polyethylene glycol effects on drug susceptibilities

目的探讨聚乙二醇（PEG）促进沙眼衣原体D—UW-5／Cx型、E—UW-5／Cx型标准株生长的最适浓度及对4种常用抗菌药物体外药物敏感性的影响。方法在沙眼衣原体D、E型菌株接种于致密单层的McCoy细胞时，加入含有不同浓度PEG的离心液，离心后在孵箱中静置2h后换成衣原体感染液，48h后固定，碘染计数包涵体数量。将沙眼衣原体接种于McCoy细胞，接种过程中用0．7％（7g／L）PEG处理菌株，McCoy细胞感染率达90％以上确定沙眼衣原体接种量后进行药敏实验。采用微量稀释法测定体外4种抗菌药物对沙眼衣原体的作用。将取自31例衣原体细胞培养阳性且基因分型为D、E型的临床标本加入或者不加入0．7％PEG，接种于致密单层的McCoy细胞后计数第1代全孔包涵体数量。结果0．7％PEG能使沙眼衣原体E型包涵体数量提高3．44倍，D型包涵体数量提高3．56倍。在体外，PEG处理过的沙眼衣原体D、E型标准株对阿奇霉素、莫西沙星、多西环素、米诺环素的最低抑菌浓度与未经PEG处理的沙眼衣原体标准株药敏结果一致。0．7％PEG可以显著增加沙眼衣原体D、E型临床标本传代产生的包涵体数量。结论0．7％PEG可以显著促进沙眼衣原体D型、E型的生长，但对药敏结果无明显影响。

Objective To optimize the concentration of polyethylene glycol （PEG） for the growth of Chlamydia trachomatis （Ct） reference strains D-UW-5/Cx and E-UW-5/Cx, and to evaluate the effects of PEG on the sensitivity of Ct to 4 common antibiotics. Methods After the inoculation of Ct standard strains （D-UW-5/Cx and E-UW-5/Cx） into McCoy cell monolayer, different concentrations of PEG were added into the culture medium followed by centrifugation. After 2 hours of incubation at 37 %, the inoculum was removed and a complete culture medium containing 1 ~Lg/mL cycloheximide was added followed by another 48-hour culture. Subsequently, the culture was fixed and subjected to iodine staining for the calculation of Ct inclusions and optimization of PEG for the growth of Ct. Some Ct standard strains were used to infect McCoy cells, with PEG （0.7%, wt/vol） added to the culture medium after inoculation and before centrifugation process, and when the infection rate reached higher than 90%, a microdilution method was utilized to evaluate the minimal inhibitory concentration （MIC） of 4 antibiotics, including azithromycin, minocyline, moxifloxacin and doxycycline. Thirty-one clinical specimens, which had been confirmed to be positive for Ct serovar D or E strain, were inoculated into McCoy cell monolayer for the passage of Ct with or without the presence of 0.7% PEG. Results The optimal concentration of PEG was 0.7% for the growth of Ct, and this concentration of PEG could increase the number of inclusion bodies of Ct serovar E by 3.44 folds, and that of Ct serovar D by 3.56 folds. In vitro, the MICs of the 4 antibiotics were consistent between PEG-treated and untreated Ct reference strains. Moreover, PEG notably increased the quantity of inclusion bodies of Ct serovar E or D from clinical specimens after passages. Conclusions PEG （0.7%） can enhance the growth of Ct serovar D and E, but has no obvious influence on antimicrobial susceptibility of Ct.