中文摘要：

目的 检测天津地区近年来大环内酯类抗生素对泌尿生殖道沙眼衣原体临床分离株的抗菌活性,筛查耐药株,从基因分子水平上探讨耐药机制.方法 将经McCoy细胞培养法检测出的42株沙眼衣原体临床株,传代培养至感染率达90%以上,收集标本进行3种常用大环内酯类抗生素的药敏试验,用RT-PCR、PCR方法分别扩增与大环内酯类耐药相关的23S核蛋白体RNA基因、核糖体蛋白L4基因,产物直接测序检测基因突变.结果 最小抑菌浓度（MIC）结果为红霉素0.5～2 mg/L,克拉霉素0.008～0.032mg/L,阿奇霉素0.125～0.5 mg/L.发现2株红霉素耐药株,MIC值为2 mg/L,2株耐药株的23SrRNA基因有C2452A、T2611C的突变（大肠杆菌序列编号）,红霉素耐药株及敏感株L4基因均发现脯氨酸113→亮氨酸、脯氨酸156→丙氨酸两个位点的突变.结论 沙眼衣原体对红霉素已产生一定的耐药性.C2452A、T2611C的突变导致红霉素低水平耐药,L4基因的点突变可能与红霉素耐药无关.

英文摘要：

Objective To test the in vitro susceptibility to macrolides of urogenital Chlamydia trachomatis （Ct） isolates, screen resistant Ct strains, and to explore resistance mechanism at the molecular level. Methods A total of 42 Ct strains were isolated from cervical or urethral swab samples and propagated in McCoy cells until the infection rate reached more than 90%. Then, susceptibility test was performed to evaluate the activity of three macrolides. Reverse transcription PCR and PCR were used to amplify two macrolide-resistance related genes, i.e., 23S rRNA gene and L4 gene, respectively in 2 erythromycin-resistant Ct strains and 4 erythromycin-sensitive strains followed by direct sequencing. Results The minimal inhibitory concentration （MIC） varied from 0.5 to 2 mg/L for erythromycin, 0.008 to 0.032 mg/L for clarithromycin, 0.125 to 0.5 mg/Lfor azithromycin. Erythromycin resistance was found in 2 isolates with the MIC value being 2 mg/L. Two mutations, C2452A and T2611A/C （Escherichia coli numbering） in the 23S rRNA gene, were detected in the resistant strains only, while the other 2 mutations, Pro113Leu and Pro156 Ala in L4 gene, were observed in all the tested strains. Conclusions Erythromycin-resistant Ct strains have emerged in clinical settings. The low-level erythromycin resistance may be associated with C2452A and T261 1C mutations in the 23S rRNA gene, whereas the point mutations in L4 gene is unlikely related to erythromycin resistance.