Bassères Eugénie, Endres Bradley T, Khaleduzzaman Mohammed, Miraftabi Faranak, Alam M Jahangir, Vickers Richard J, Garey Kevin W
University of Houston College of Pharmacy, 1441 Moursund Street, Houston, TX 77030, USA.
Summit Therapeutics, 85b Park Drive, Milton Park, Abingdon, Oxfordshire OX14 4RY, UK.
J Antimicrob Chemother. 2016 May;71(5):1245-51. doi: 10.1093/jac/dkv498. Epub 2016 Feb 18.
Ridinilazole (SMT19969) is a narrow-spectrum, non-absorbable antimicrobial with activity against Clostridium difficile undergoing clinical trials. The purpose of this study was to assess the pharmacological activity of ridinilazole and assess the effects on cell morphology.
Antibiotic killing curves were performed using the epidemic C. difficile ribotype 027 strain, R20291, using supra-MIC (4× and 40×) and sub-MIC (0.125×, 0.25× and 0.5×) concentrations of ridinilazole. Following exposure, C. difficile cells were collected for cfu counts, toxin A and B production, and morphological changes using scanning electron and fluorescence microscopy. Human intestinal cells (Caco-2) were co-incubated with ridinilazole-treated C. difficile growth medium to determine the effects on host inflammatory response (IL-8).
Treatment at supra-MIC concentrations (4× and 40× MIC) of ridinilazole resulted in a significant reduction in vegetative cells over 72 h (4 log difference, P < 0.01) compared with controls without inducing spore formation. These results correlated with a 75% decrease in toxin A production (P < 0.05) and a 96% decrease in toxin B production (P < 0.05). At sub-MIC levels (0.5× MIC), toxin A production was reduced by 91% (P < 0.01) and toxin B production was reduced by 100% (P < 0.001), which resulted in a 74% reduction in IL-8 release compared with controls (P < 0.05). Sub-MIC (0.5×)-treated cells formed filamentous structures ∼10-fold longer than control cells. Following fluorescence labelling, the cell septum was not forming in sub-MIC-treated cells, yet the DNA was dividing.
Ridinilazole had robust killing effects on C. difficile that significantly reduced toxin production and attenuated the inflammatory response. Ridinilazole also elicited significant cell division effects suggesting a potential mechanism of action.
瑞地那唑（SMT19969）是一种窄谱、不可吸收的抗菌药物，对艰难梭菌具有活性，正在进行临床试验。本研究的目的是评估瑞地那唑的药理活性并评估其对细胞形态的影响。
使用流行的艰难梭菌核糖体分型027菌株R20291，采用高于最低抑菌浓度（4倍和40倍）以及低于最低抑菌浓度（0.125倍、0.25倍和0.5倍）的瑞地那唑浓度绘制抗生素杀菌曲线。暴露后，收集艰难梭菌细胞进行菌落形成单位计数、毒素A和B的产生检测，并使用扫描电子显微镜和荧光显微镜观察形态变化。将人肠道细胞（Caco-2）与经瑞地那唑处理的艰难梭菌生长培养基共同孵育，以确定其对宿主炎症反应（IL-8）的影响。
与未诱导孢子形成的对照组相比，用高于最低抑菌浓度（分别为4倍和40倍最低抑菌浓度）的瑞地那唑处理72小时后，营养细胞显著减少（相差4个对数，P<0.01）。这些结果与毒素A产生减少75%（P<0.05）和毒素B产生减少96%（P<0.05）相关。在低于最低抑菌浓度（0.5倍最低抑菌浓度）水平时，毒素A产生减少91%（P<0.01），毒素B产生减少100%（P<0.0），与对照组相比，IL-8释放减少74%（P<0.05）。经低于最低抑菌浓度（0.5倍）处理的细胞形成的丝状结构比对照细胞长约10倍。荧光标记后，经低于最低抑菌浓度处理的细胞中细胞隔膜未形成，但DNA仍在分裂。
瑞地那唑对艰难梭菌具有强大的杀伤作用，可显著降低毒素产生并减轻炎症反应。瑞地那唑还引发了显著的细胞分裂效应，提示了一种潜在的作用机制。
