Freeman Jane, Baines Simon D, Saxton Katie, Wilcox Mark H
Department of Microbiology, Leeds Teaching Hospital and University of Leeds, Leeds LS1 3EX, UK.
J Antimicrob Chemother. 2007 Jul;60(1):83-91. doi: 10.1093/jac/dkm113. Epub 2007 May 5.
We compared the behaviour of Clostridium difficile PCR ribotypes 001 and 027 in a human gut model, and compared the responses to metronidazole exposure.
Using a human gut model primed with pooled human faeces, gut flora bacterial counts, C. difficile total viable counts, spore counts and cytotoxin titres were determined, following exposure to clindamycin, in the absence or presence of metronidazole.
Duration of cytotoxin production by C. difficile ribotype 027 was markedly longer than that of ribotype 001 (23 versus 13 days, respectively), but peak toxin titres were similar. During toxin production, total C. difficile ribotype 027 populations had higher proportions of vegetative cells than did ribotype 001 (median 56.33 versus 23.54%). Similarly, total C. difficile ribotype 027 populations remained predominantly as vegetative cells for longer than did ribotype 001 (20 versus 9 days). The effects of metronidazole on C. difficile were markedly less than expected. Titres of C. difficile ribotype 001 cytotoxin were reduced but recurred following metronidazole administration. C. difficile ribotype 027 cytotoxin titres in the distal section of the gut model were unaffected by metronidazole. These observations correlated with poor metronidazole concentrations.
Duration of cytotoxin production by C. difficile ribotype 027 markedly exceeds that of ribotype 001. Sub-optimal gut concentrations of metronidazole, possibly due to inactivation by components of normal gut flora, are associated with continued toxin production. These findings may help to explain the increased severity of symptoms and higher case-fatality ratio associated with infections due to C. difficile ribotype 027.
我们在人体肠道模型中比较了艰难梭菌PCR核糖型001和027的行为，并比较了它们对甲硝唑暴露的反应。
使用接种了混合人粪便的人体肠道模型，在不存在或存在甲硝唑的情况下，测定暴露于克林霉素后肠道菌群细菌计数、艰难梭菌总活菌数、孢子数和细胞毒素滴度。
艰难梭菌核糖型027产生细胞毒素的持续时间明显长于核糖型001（分别为23天和13天），但毒素峰值滴度相似。在毒素产生期间，艰难梭菌核糖型027总菌群体中营养细胞的比例高于核糖型001（中位数分别为56.33%和23.54%）。同样，艰难梭菌核糖型027总菌群体以营养细胞为主的时间比核糖型001更长（分别为20天和9天）。甲硝唑对艰难梭菌的影响明显小于预期。艰难梭菌核糖型001细胞毒素滴度降低，但在给予甲硝唑后又复发。肠道模型远端部分的艰难梭菌核糖型027细胞毒素滴度不受甲硝唑影响。这些观察结果与甲硝唑浓度不足有关。
艰难梭菌核糖型027产生细胞毒素的持续时间明显超过核糖型001。甲硝唑在肠道中的浓度不理想，可能是由于被正常肠道菌群成分灭活，这与毒素持续产生有关。这些发现可能有助于解释与艰难梭菌核糖型027感染相关的症状加重和更高病死率。
