2005-2008年上海分离肺炎支原体对抗菌药物的敏感性及对大环内酯类的耐药机制研究

In vitro antimicrobial susceptibility of Mycoplasma pneumoniae and mechanism of macrolide resistance for isolates obtained in Shanghai from 2005 to 2008

目的了解目前上海分离肺炎支原体对常用抗菌药的敏感性，明确对红霉素耐药株的耐药机制。方法采用微量稀释法测定102株肺炎支原体对大环内酯类、四环素类和氟喹诺酮类的药物敏感性。对肺炎支原体核糖体23SrRNA全序列进行扩增及测序。采用限制性片段长度多态性分析（PCR—RFLP）对肺炎支原体进行分型。结果四环素类及氟喹诺酮类对肺炎支原体具有良好活性。肺炎支原体临床分离株对红霉素敏感性低，MIC50和MIC90均〉128μg/ml。81．4％（83／102）临床株对红霉素耐药（MIC均〉128mg/L）。红霉素耐药肺炎支原体均存在A2063G的核苷酸位点突变。85．3％（87／102）临床分离株属于RFLP1型。结论上海分离肺炎支原体对红霉素耐药率高，核糖体23SrRNA的A2063G核苷酸点突变是导致耐药的原因。

Objective To learn the current in vitro antimicrobial susceptibility of Mycoplasma pneumoniae in Shanghai and to understand the mechanisms of resistance to macrolides. Methods M. pneumoniae was isolated from pediatric patients with low respiratory tract infections （RTI） using broth and PPLO agar medium. PCR amplification and sequence analysis of P1 adhesion gene were performed to identify all M. pneumoniae strains. Susceptibility testing was carried out for macrolides, tetracyclines and fluoroquinolones using broth microdilution method with SP4 broth. PCR amplification and sequence analysis of 23S rRNA genes were performed for all M. pneumoniae strains. P1 gene PCR-RFLP typing was performed to subtype the M. pneumoniae strains. Results One hundred and two M. pneumoniae strains were isolated in Shanghai from Oct 2005 to Dee 2008. All M. pneumoniae isolates were susceptible to the tetracyclines and fluoroquinolones tested. Of 102 clinical isolates, 83（81.4% ） was resistant to erythromycin and all 83 erythromycin-resistant strains had MIC 〉 128 mg/L. An increasing trend of resistance rates were showed： 16.7% （1/6） in 2005, 76.5% （13/17） in 2006, 100.0% （24/24） in 2007 and 81, 8% （45/55） in 2008. All macrolide-resistant M. pneumoniae strains harbored an A2063G transition mutation in domain V of 23S rRNA genes. The P1 gene RFLP type 1 is predominant （85.3% , 87/102） in M. pneumoniae clinical isolates. Conclusion The macrolide resistance rate of M. pneumoniae is very high in Shanghai. The mechanism of macrolide resistance is associated with transition mutation on the 23S rRNA gene.