Microbiology, DIMES, University of Bologna, Bologna, Italy.
J Antimicrob Chemother. 2018 Feb 1;73(2):409-413. doi: 10.1093/jac/dkx392.
Rectal Chlamydia trachomatis infections represent one of the most common sexually transmitted infections in the MSM population. Although current treatment guidelines suggest the use of either azithromycin or doxycycline, several clinical studies reported on azithromycin treatment failures in the case of rectal C. trachomatis localizations. In this context, the biological reasons behind the lack of azithromycin efficacy for C. trachomatis infections at the rectal level are still poorly understood.
To evaluate the in vitro antimicrobial susceptibility of several C. trachomatis strains in two different cell lines, mimicking the urogenital localization and the rectal site of infection.
The susceptibility to macrolides (i.e. azithromycin and erythromycin), doxycycline and levofloxacin was assessed for 20 C. trachomatis strains, belonging to the most frequently reported genovars (D, E, F and G), both in human endocervical cells (HeLa cells) and in colorectal cells (Caco-2 cells). Moreover, a correlation between MIC values and C. trachomatis bacterial load was investigated in both cell lines.
For all the C. trachomatis strains, regardless of the genovar, macrolides showed higher MIC and MBC values (2-fold dilutions) in Caco-2 cells compared with HeLa cells, whereas for doxycycline and levofloxacin, no significant differences were found between the two cell lines. Moreover, azithromycin MICs were significantly higher with increasing levels of C. trachomatis elementary bodies on Caco-2 cells.
The higher azithromycin MICs observed in colorectal cells, together with the positive correlation between MICs and C. trachomatis loads found, could explain azithromycin treatment failure for C. trachomatis infections at the rectal site.
直肠沙眼衣原体感染是男男性行为者人群中最常见的性传播感染之一。尽管目前的治疗指南建议使用阿奇霉素或强力霉素，但一些临床研究报告了阿奇霉素治疗直肠沙眼衣原体局部感染失败的情况。在这种情况下，直肠水平沙眼衣原体感染缺乏阿奇霉素疗效的生物学原因仍知之甚少。
评估两种不同细胞系中几种沙眼衣原体株的体外抗菌药敏性，模拟泌尿生殖道定位和直肠感染部位。
对 20 株沙眼衣原体株（属于最常报告的 D、E、F 和 G 基因亚型）进行大环内酯类（即阿奇霉素和红霉素）、强力霉素和左氧氟沙星的药敏性评估，分别在人宫颈癌细胞（HeLa 细胞）和结直肠癌细胞（Caco-2 细胞）中。此外，还研究了两种细胞系中 MIC 值与沙眼衣原体细菌负荷之间的相关性。
对于所有沙眼衣原体株，无论基因亚型如何，大环内酯类药物在 Caco-2 细胞中的 MIC 和 MBC 值（2 倍稀释）均高于 HeLa 细胞，而对于强力霉素和左氧氟沙星，两种细胞系之间无显著差异。此外，在 Caco-2 细胞上，随着沙眼衣原体原体数量的增加，阿奇霉素的 MIC 值显著升高。
在结直肠细胞中观察到的阿奇霉素 MIC 值较高，以及 MIC 值与沙眼衣原体负荷之间的正相关关系，可能解释了阿奇霉素治疗直肠沙眼衣原体感染失败的原因。
