Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197 Ruijin ER Road, Shanghai, China.
Int J Antimicrob Agents. 2013 Jan;41(1):80-4. doi: 10.1016/j.ijantimicag.2012.08.011. Epub 2012 Nov 11.
Clostridium difficile is a predominant cause of antibiotic-associated diarrhoea. It is increasingly difficult to treat C. difficile infection efficiently owing to its multidrug resistance. In the present study, 60 clinical C. difficile isolates were collected and analysed for their genotype, antimicrobial susceptibility and resistance mechanisms. Tandem repeat sequence typing (TRST) generated 21 types, including the epidemic clone tr017. Antimicrobial susceptibility testing of eight antibiotics was performed by the agar dilution method. Rifampicin, metronidazole and vancomycin remained the most potent agents in vitro, whilst the resistance rates of other agents such as ciprofloxacin, cefoxitin, clindamycin, tetracycline and moxifloxacin varied from 30% to 100%. 73.33% of the strains were multiresistant to at least three classes of antibiotics, and tr017 strains made up the greatest proportion of multidrug resistance. By further investigating the resistance mechanisms, amino acid substitutions in target enzymes encoded by gyrA/gyrB and rpoB were observed in fluoroquinolone- and rifampicin-resistant strains, respectively. The erm(B) gene was the most prevalent in macrolide-lincosamide-streptogramin B (MLS(B))-resistant strains, and the ErmB determinant 'Erj2', a novel genetic organisation identified in this study, plays a central role in conferring resistance, especially in epidemic strains. Moreover, transposon Tn916 carrying the tet(M) gene is more common than Tn5397 in tetracycline resistance.
艰难梭菌是抗生素相关性腹泻的主要原因。由于其具有多种药物耐药性，因此越来越难以有效地治疗艰难梭菌感染。在本研究中，收集了 60 株临床艰难梭菌分离株，并对其基因型、抗菌药物敏感性和耐药机制进行了分析。串联重复序列分型（TRST）产生了 21 种类型，包括流行克隆 tr017。采用琼脂稀释法对 8 种抗生素进行了药敏试验。利福平、甲硝唑和万古霉素在体外仍然是最有效的药物，而其他药物如环丙沙星、头孢西丁、克林霉素、四环素和莫西沙星的耐药率从 30%到 100%不等。73.33%的菌株对至少三类抗生素具有多药耐药性，tr017 菌株构成了多药耐药的最大比例。通过进一步研究耐药机制，观察到氟喹诺酮类和利福平耐药株中靶酶编码基因 gyrA/gyrB 和 rpoB 的氨基酸替换。erm(B)基因是大环内酯-林可酰胺-链阳性菌素 B（MLS(B)）耐药株中最常见的基因，而 ErmB 决定簇 'Erj2'，是本研究中鉴定的一种新的遗传组织，在赋予耐药性方面发挥着核心作用，特别是在流行株中。此外，携带 tet(M)基因的转座子 Tn916 比 Tn5397 更常见于四环素耐药性。
