医院获得性感染中出现携带SCCmec Ⅳ/Ⅴ的耐甲氧西林金黄色葡萄球菌（英文）

Emergence of methicillin-resistant Staphylococcus aureus SCCmec type Ⅳ/Ⅴ epidemic clones in a large teaching hospital in China

目的研究某院临床分离的医院获得性耐甲氧西林金黄色葡萄球菌(HA-MRSA)的葡萄球菌染色体mec盒(SCCmec)分型及分子流行病学特征。方法收集中南大学湘雅医院2012年1月~2012年12月临床分离的71株HA-MRSA,采用多重PCR进行SCCmec分型,PCR检测PVL毒素基因,并用脉冲场凝胶电泳(PFGE)分析菌株间的同源性。结果 71株HA-MRSA以SCCmecⅢ型为主,占69.0%(49/71),其次为SCCmecⅣ型、SCCmecⅤ型和SCCmecⅡ型,分别占14.1%(10/71)、4.2%(3/71)和4.2%(3/71),另有6株(8.5%)菌株未能分型。HA-SCCmecⅣ/ⅤMRSA感染者年龄显著低于HA-SCCmecⅠ/Ⅱ/ⅢMRSA感染者,携带PVL基因阳性率显著高于HA-SCCmecⅠ/Ⅱ/ⅢMRSA感染者,而两者入院至检出菌株的时间及住院天数均未见明显差异。HA-SCCmecⅣ/ⅤMRSA对左旋氧氟沙星、环丙沙星、利福平、庆大霉素、四环素等的耐药率均显著低于HA-SCCmecⅠ/Ⅱ/ⅢMRSA(P<0.05)。13株HA-SCCmecⅣ/ⅤMRSA菌株在55%的相似度水平形成一个大的组群。按照≥85%的相似度,这些菌株共形成3个PFGE簇以及4个单一菌株的PFGE型。结论在国内首次发现携带SCCmecⅤ型的HA-MRSA菌株,HASCCmecⅣ/ⅤMRSA已有在医疗机构传播的趋势,并成为医院内感染的重要来源。

Objective To investigate the staphylococcal cassette chromosome mec （SCCmec） genotype and molecular epidemiological characteristics of healthcare-associated methicillin-resistant Staphylococcus aureus （HA-MRSA） in a large teaching hospital in China. Methods From January 2012 to December 2012, a total of 71 nonduplicate HA-MRSA were collected in a teaching hospital in Changsha, China. SCCmec types were determined by multiplex PCR, and Panton-Valentine leukocidin （PVL） gene was detected by PCR. The homology among the tested isolates was determined using pulsed-field gel electrophoresis （PFGE）. Results Of the 71 HA-MRSA isolates, 49 （69.0%） carried SCCmec Ⅲ, 10 （14.1%） carried SCCmec IV, 3 （4.2%） carried SCCmec V and 3 （4.2%） carried SCCmec II;the remaining 6 isolates were not typeable by PCR. Compared with patients having SCCmec Ⅰ/Ⅱ/Ⅲ MRSA infections, those with SCCmec IV/V MRSA infections had a significantly younger age and a similar duration of hospital stay before the first MRSA-positive culture and total hospital stay. PVL genes were strongly associated with SCCmec type IV/V MRSA infections. HA-SCCmec IV/V MRSA strains showed a greater susceptibility to rifampicin, gentamicin, levofloxacin, ciprofloxacin, and tetracycline than HA-SCCmec Ⅰ/Ⅱ/Ⅲ MRSA strains. The 13 HA-SCCmec IV/V MRSA isolates formed one large group at the 55%similarity level. Three PFGE clusters with a similarity index of 85%or more were identified, and unique PFGE profiles were observed in 4 isolates. Conclusions This is the first report of HA-MRSA isolates carrying SCCmec V in Chinese hospitals. SCCmec types IV and V MRSA clones have emerged in Chinese hospitals, which urges more rigorous surveillance of their spread in healthcare facilities in China.