血流感染中分离的耐甲氧西林溶血葡萄球菌的药物敏感性、SCCmec基因分型及同源性分析

摘要：目的 调查分析本地区血流感染中分离耐甲氧西林溶血葡萄球菌(MRSH)的药物敏感性、葡萄球菌盒染色体mec(SCCmec)分型及分子流行病学特征。方法 收集2013年1月1日—2014年12月31日湖南省20家三甲医院血流感染患者的MRSH 78株，采用微量肉汤稀释法进行体外药敏试验；PCR扩增mecA基因及SCCmec基因；脉冲场凝胶电泳(PFGE) 检测MRSH的同源性。结果 78株MRSH中，96.1%的菌株存在mecA基因，MRSH对红霉素、左氧氟沙星和克林霉素的耐药率分别为94.9%、80.7%和53.8%，2株对利奈唑胺耐药，1株对替考拉宁耐药，没有菌株对万古霉素耐药。SCCmec可分型为50%(39/78)，不可分型为50%(39/78)。39株可分型菌株中，单个SCCmec类型以Ⅰ型为主(18/39，46.1%)，混合型SCCmec类型以Ⅰ+Ⅱ型为主(12/39，30.8%)。PFGE带型整体较为分散，但有6组菌株间存在100%同源性。结论 本地区血流感染中MRSH的耐药形势严峻；在SCCmec可分型的菌株中，以Ⅰ型SCCmec为主，SCCmec多样且不同SCCmec型别之间的耐药性存在差异；本地区MRSH以散发为主，但存在院间及院内交叉感染的可能性，应加强对其监测，减少MRSH的进一步传播。

Antimicrobial susceptibility,SCCmec typing,and homology analysis of methicillin-resistant Staphylococcus haemolyticus isolated from bloodstream infections

Abstract Objective To investigate and analyze the antimicrobial sensitivity, staphylococcal chromosome cassette mec (SCCmec) typing and molecular epidemiological characteristics of methicillin-resistant Staphylococcus haemolyticus (MRSH) isolated from bloodstream infections. Methods A total of 78 MRSH isolates were collected consecutively from bloodstream infection patients in 20 tertiary hospitals in Hunan province during 2013—2014. The antimicrobial sensitivity tests were performed in vitro using the microbroth dilution method. The mecA and SCCmec were amplified by PCR. All MRSH isolates were characterized by pulsed-field gel electrophoresis (PFGE). Results Of the 78 MRSH strains, 96.1% had mecA gene. The resistance rates of MRSH to erythromycin, levofloxacin, and clindamycin were 94.9%, 80.7% and 53.8% respectively, two strains were resistant to linezolid, one strain was resistant to teicoplanin, and no strain was resistant to vancomycin. The results of SCCmec genotyping showed that SCCmec can be classified as typeable (50%, 39/78) and untypeable (50%, 39/78). Among the 39 genotypeable strains, type I was the main type of single SCCmec (18/39, 46.2%), and type Ⅰ + Ⅱ was the main type of mixed SCCmec (13/39, 30.8%). The PFGE banding patterns were scattered as a whole, but there were 100% homology among six groups of strains. Conclusion The situation of drug resistance of MRSH in bloodstream infections in this area is serious. Among the strains that can be typed by SCCmec, type I SCCmec is dominant. SCCmec is diverse and drug resistance is different among different SCCmec types. MRSH in this area is mainly sporadic, but there is the possibility of inter-hospital and intra-hospital cross infections, and thus surveillance should be strengthened to reduce the further spread of MRSH.