耐甲氧西林金黄色葡萄球菌感染的流行病学研究

目的了解某院患者耐甲氧西林金黄色葡萄球菌（MRSA）的感染和医院环境中MRSA的污染情况，研究临床和相应环境标本中MRSA的同源性，寻找MRSA医院感染的传染源及传播途径。方法采用Vitek-2细菌鉴定系统鉴定金黄色葡萄球菌；以头孢西丁纸片琼脂扩散法和mecA基因聚合酶链反应（PCR）鉴定MRSA随机扩增多态性DNA（RAPD）技术进行同源性分析。结果临床标本分离的金黄色葡萄球菌中，MRSA占58．54％（24／41）；环境标本分离的金黄色葡萄球菌中，MRSA占38．10％（16／42）。MRSA菌株经RAPD扩增后均可见数量不等（4～6条）的条带，分型率达100％。经聚类分析，24株临床MRSA菌株分为4型，其中以RAPDⅠ型为主（14株）；16株环境MRSA菌株分为3型，亦以RAPDⅠ型为主（13株）。烧伤科与神经外科各有4例患者及其周围环境分离出同源菌。结论该院临床标本及医院环境标本中MRSA分离率较高，RAPDⅠ型MRSA为其主要流行株且存在RAPDⅠ型MRSA菌株克隆传播。外源性途径是MRSA医院感染的主要来源。

Epidemiological study on infection of methicillin resistant Staphylococcus aureus

Objective To investigate the infection of methicillin-resistant Staphylococcus aureus （MRSA） in patients in a hospital and environmental contamination of MRSA, and study the possible sources and transmission routes with homology analysis of MRSA isolates collected from patients and environment. Methods Staphylococcus aureus were identified by Vitek-2 system, MRSA were identified by cefoxitin disk diffusion method and mecA PCR, homology of MRSA isolates was analysed with randomly amplified polymorphic DNA （RAPD） analysis. Results A- mong all isolates of Staphylococcus aureus, the isolation rate of MRSA from clinical and environmental samples was 58. 54% （24/41）and 38. 10%（16/24） respectively. The numbers of amplified DNA fragments by RAPD were 4- 6, typing rate was 100%. Based on clustering analysis, 24 clinical strains were divided into 4 types,and the main type was type Ⅰ （14 strains） ; 16 environmental strains were divided into 3 types, and the main type was also type Ⅰ （13 strains）. 4 patients in burn unit and 4 patients in neurosurgical department and environment isolated homologous strains. Conclusion The isolated rate of MRSA in patients and environment in this hospital was high, the dominant epidemic strain of MRSA was type Ⅰ and clone spread might exist. Extrinsic route was the main source for nosocomial infection caused by MRSA.