下呼吸道标本MRSA耐药性及分子流行病学研究

目的了解下呼吸道标本中MRSA的耐药性及分子流行病学特点。方法采用Kirby-Bauer纸片扩散法，对我院2005年12月至2006年12月下呼吸道标本分离的107株MRSA药敏结果进行分析；采用脉冲场凝胶电泳（PFGE）对其中32株MRSA进行同源性分析。结果107株MRSA对14种抗菌药物的药敏结果显示对万古霉素、替考拉宁和利奈唑胺均敏感；对奎奴普丁-达福普汀和利福平显示较好的敏感性，敏感率分别为93．5％、70．1％；其次为对氯霉素敏感率54．2％；对四环素、庆大霉素、克林霉素和左氧氟沙星等显示高度耐药或全耐药。PFGE分析表明32株MRSA分为4个PFGE组（A～D型），25株为A型，A型又包括A1、A2、和A33个亚型，其中以A1亚型为主，共17株，A2亚型1株，A3亚型7株，B型5株，C型1株，D型1株。结论我院在2005年12月到2006年12月ICU、结核5科有MRSA暴发流行，主要流行株为A1、A3亚型；这些MRSA菌株为多重耐药菌，应引起临床医师及感染控制部门高度重视。

Antibiotic resistance and molecular epidemiology of methicillin-resistant Staphylococcus aureus isolated from lower respiratory tract

Objective To investigate the antibiotic resistance and molecular epidemiology profiles of methicillin-resistant Staphylococcus aureus （MRSA） isolated from lower respiratory tract. Methods A total of 107 MRSA strains were isolated from lower respiratory tract specimen at Shanghai Pulmonary Hospital between December 2005 and December 2006. The antibiotic resistance was determined by Kirby-Bauer agar dilution. We also performed homology analysis for 32 of the MRSA strains using pulsed-field gel electrophoresis （PFGE）. Results The susceptibility of the 107 MRSA strains to antibiotics was as follows： 100% susceptible to vancomycin, teicoplanin and linezolid; 93.5% and 70. 1 % susceptible to quinupristin-dalfopristin and rifampin respectively; 54. 2% susceptible to chloramphenicol： 100% resistant to tetracycline, gentamicin, clindamycin, levofloxacin. PFGE analysis identified 4 PFGE patterns from the 32 MRSA strains： pulsotype A （25 strains）, including subtype A1 （17 strains）, subtype A2 （1 strain）, subtype A3 （7 strains） ; pulsotype B （5 strains）, pulsotype C （1 strain）, and pulsotype D （1 strain）. Conclusions There may be outbreaks of MRSA in ICU and TB Ward 5 at Shanghai Pulmonary Hospital between December 2005 and December 2006, which deserves attention from both clinical staff and infection control department. The major causes of the epidemic genotypes are subtype A1 and subtype A3. Most of the MRSA strains were multi-drug resistant.