医院环境及临床分离MRSA分子流行病学研究

Study on the molecular epidemiology of MRSA isolated from hospital environment and clinical specimens

目的研究医院环境及临床分离耐甲氧西林金黄色葡萄球菌(MRSA)分子流行病特征,为MRSA的医院感染防控提供依据。方法使用MicroScan walkaway-40SI全自动微生物分析仪对医院环境与临床分离MRSA进行鉴定。通过多重PCR扩增特异基因片段进行SCCmec基因分型,并应用spa分型技术进行同源性分析。结果 SCCmec分型结果显示,环境分离的7株MRSA分为两型:其中SCCmecⅢ型6株;SCCmecⅣ型1株。临床分离44株MRSA分为四型:其中SCCmecⅡ型8株、Ⅲ型22株、Ⅳ型12株、Ⅴ型1株,未检出Ⅰ型菌株,并有1株未能分型。SCCmecⅢ型MRSA主要分布在新生儿监护病房(NICU)、呼吸内科、重症监护病房(ICU)和神经外科。对MRSA进行spa基因分型可见:NICU主要流行株为t437型,呼吸内科主要流行株为t030型,而ICU和神经外科流行株均为t034型,且上述科室环境与临床分离株高度同源。结论医院环境与临床分离的MRSA均以SCCmecⅢ型为主。spa分型结果显示两类MRSA同源性较高,科室之间存在同型MRSA的交叉传播。MRSA定植于医院环境是导致其医院感染流行传播的重要因素。

Objective To research the molecular epidemiology of MRSA isolated from hospital environment and clinical specimens, in order to provide the evidence for preventing and controling the nosocomial infection caused by MRSA. Methods The identified MRSA isolated from clinical specimens and hospital environment were performed by MieroScan walkaway-40SI automatic microbial analyzer. The SCCmee types were determined by amplifying the characteristics gene fragments using multiplex PCR. The homology of MRSA was analyzed basing on spa typing results. Results The SCCmec typing results showed that 7 strains of MRSA isolated from hospital environ- ment were divided into type Ⅲ （6 strains） and type Ⅳ （ 1 strain）. The 44 strains of MRSA isolated from clinical specimens were constituted with type Ⅱ （8 strains ）, type Ⅲ （22 strains）, type Ⅳ （ 12 strains ） and typeⅤ （ 1 strains）. The type Ⅰ was not detected and one strain had failed to type. The strains typed SCCmec m were distributed in department of neonatal intensive care unit （NICU）, department of respiratory, department of intensive care unit （ICU）, department of neurosurgery. The strains typed SCCmeclVwere distributed in department of emergency surgery, department of general surgery. To analyze the spa genotypes of the MRSA isolated from NICU, department of respiratory, ICU and department of neurosurgery, the data showed that the t437 was the predominant type in NICU, and the t030 was the predominant type in department of Respiratory, while the t034 was the predominant type both in ICU and in department of neurosurgery. Moreover, we found that the strains isolated from environmental and clinical were highly homologous in different departments described above. Conclusion The MRSA isolated from clinical specimens and hospital environment are primarily SCCmec m type. The spa typing shows that the MRSA have highly homology between clinical strains and environmental strains. The same type of MRSA isolated from different clinical departments may caused by cross-infection. MRSA colonized in hospital environment is an important factor in its nosoeomial spreading.