临床分离艰难梭菌188株的耐药性研究

Antimicrobial resistance in 188 clinical isolates of Clostridium difficile

目的了解艰难梭菌临床分离株对抗菌药物的耐药性及耐药机制。方法以琼脂稀释法测定甲硝唑等12种抗菌药物对2007年3月～2009年3月复旦大学附属华山医院临床分离的艰难梭菌的体外抗菌活性;PCR扩增及DNA测序比对检测耐药基因及耐药决定区突变。结果 188株菌株包括25种核糖型别,以核糖型017最为常见(25%),其次为001与012。未检测到核糖型027,但有1株细菌为核糖型078。所有菌株均对甲硝唑、万古霉素和哌拉西林-他唑巴坦敏感,对莫西沙星、环丙沙星、左氧氟沙星、红霉素、克林霉素、四环素、利福平、利福昔明和夫西地酸的耐药率分别为50.0%、100%、70.7%、77.7%、83.0%、47.9%、19.8%、19.8%和12.8%。主要核糖型菌株耐药性更高。耐药株中耐药基因或耐药决定区突变检出率分别为:ermB基因76%;tetM基因97.8%;gyrA基因突变59.6%;g了rB基因突变11.7%;g了rA与gyrB基因同时突变28.7%;rpoB基因突变100%。仅在2株夫西地酸耐药株中检测到fusA基因突变。结论艰难梭菌对甲硝唑与万古霉素仍呈现敏感,但对氟喹诺酮类药物及红霉素等呈现较高的耐药率。核糖型017等流行株对莫西沙星、利福平等抗菌药物耐药率更高。

Objective To investigate the antimicrobial susceptibility patterns and resistance mechanisms of Clostridiuzn difficile clinical isolates. Methods Toxigenic C. difficile isolates collected from Huashan Hospital of Fudan University between March 2007 and March 2009 were analyzed for their antibiotic susceptibility patterns using agar dilution method. The molecular basis of antibiotic resistance was investigated using polymerase chain reaction （PCR） and DNA sequencing. Results Of the 188 iso- lates, 25 different PCR ribotypes were identified with a dominant clone 017 accounting for 25 % of the isolates, followed by 001 and 012. Ribotype 027 was not found but 1 isolate belonged to ribotype 078. All the isolates were susceptible to metronidazole, vancomycin and piperacillin-tazobactam. Resistance to moxifloxacin, ciprofloxacin, levofloxacin, erythromycin, clindamycin, tetracycline, rifampin, rifaximin and fusidic acid was found in 50. 0%, 100%, 70. 7%, 77.7%, 83. 0%, 47.9%, 19.8%, 19.8% and 12.8% of the isolates, respectively. The isolates of common PCR ribotypes were more resistant than the uncommon ribotypes. The prevalence of resistance genes and mutations among the resistant isolates was as follows., errnB, 76%; terM, 97.8% ; gyrA mutation, 59.6% ; gyrB mutation, 11.7% ; gyrA and gyrB mutation, 28.7% ; rpoB mutation, 100%. The fusA mutation was only found in 2 isolates. Conclusions C. difficile isolates are still susceptible to metronidazole and vancomycin. However, high rates of fluoroquinolones and erythromycin resistance have been observed. Isolates of common PCR ribotypes are more resistant than uncommon ribotypes, especially the dominant strain 017.