中国七城市儿童耐甲氧西林金黄色葡萄球菌感染分离株分子学特征的研究

目的 探讨我国7个城市儿童耐甲氧西林的金黄色葡萄球菌(MRSA)感染分离株的分子特征.方法 收集2005至2009年全国7个城市(北京、上海、深圳、广州、温州、沈阳、重庆)9所三级儿童医院分离的134株MRSA.采用PCR和测序对MRSA进行多位点序列分型(MLST)和spa分型,采用多重PCR进行SCCmec分型,同时检测pvl基因.结果 MRSA大多数来源于肺炎和皮肤软组织感染分离株,占82.1％;共检测到16个MLST型,最主要的ST型是ST59 (44.8％),其次是ST239(16.4％);SCCmec分型共有Ⅱ、Ⅲ、Ⅳ和Ⅴ型4型,其中Ⅳ型是最常见的SCCmec型(50.0％),其次是Ⅴ型(23.9％)和Ⅲ型(23.9％),Ⅳ型中最常见的亚型是Ⅳa(77.6％);检测到26种spa分型,最重要的spa型是t437 (47.8％);菌株的pvl携带率与菌株SCCmec分型有关,SCCmecⅣ和Ⅴ型菌株的pvl携带率大于Ⅱ和Ⅲ型(58.6％ vs.14.3％,P＜0.05),且差异有统计学意义.不同疾病来源和不同地区来源的菌株,其流行克隆不同.结论 2005至2009年我国儿童MRSA感染分离株的流行克隆为ST59-MRSA-Ⅳa(t437)和ST239-MRSA-Ⅲ(t037),可能分别属于社区获得性MRSA与医院获得性MRSA.因此,开展对于MRSA临床流行病学监测和分子生物学的研究十分必要,能够为制定本地区防治措施提供循证依据,从而有效降低MRSA在社区和医院内的发病.

Molecular characteristics of methicillin resistant Staphylococcus aureus isolated from Chinese children

Objective To investigate the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates from Chinese children in seven cities. Method A total of 134 MRSA isolates were collected from nine hospitals.Multilocus sequence typing and spa typing were analyzed by polymerase chain reaction (PCR),and staphylococcal chromosomal cassette mec (SCCmec) type was analyzed by multiplex PCR.The Panton-Valentine leukocidin (pvl) gene was also detected.Result Most MRSA strains were isolated from pneumonia and skin and soft tissue infection (SSTIs) patients,accounting for 82.1％.Overall,16 sequence types (STs) were obtained,and CC59 (51.7％) was found to be the most prevalent,which included ST 59 and ST 338,followed by ST239 ( 16.4％ ).SCCmec types Ⅱ,Ⅲ,Ⅳ,and Ⅴ were also identified in the current study. SCCmec type Ⅳ was the most predominant type at 50.0％,followed by SCCmec type Ⅴ at 23.9％ and Ⅲ at 23.9％.SCCmec subtypes Ⅳa,Ⅳc,and Ⅳg were found among SCCmec type Ⅳ strains,whereas Ⅳ a was the main subtype at 77.6％.Twenty-six spa types were also identified,among which the predominant type was t437 (47.8％).The prevalence of pvl genes and the SCCmec type of strain was relevant,and the pvl gene positive rate was higher in SCCmec type Ⅳ and Ⅴ-type strains than in SCCmec type Ⅱ and Ⅲ strains (58.6％ vs.14.3％,P ＜0.05) ; there was a significant difference between them. In the strains isolated from pneumonia and SSTIs,ST59-MRSA-Ⅳa (t437) was the predominant clone. There were five clones detected from the strains isolated from septicemia,with ST59-MRSA-Ⅳ a(t437) and ST59-MRSA-Ⅴ (t437) as the main clones (57.1％ ).Various predominant clones existed in different regions.ST59-MRSA-Ⅳa(t437) was the prevalent clone in the Guangzhou,Beijing,Chongqing,and Shenzhen areas,whereas ST239-MRSA-Ⅲ (t037)was the prevalent clone in the Shanghai area.Fifty percent of the isolates from the Wenzhou area belonged to ST910- MRSA-Ⅴ (t318),whereas three clinical strains isolated from the Shenyang region belonged to three different types.Conclusion The results indicate that MRSA isolates from Chinese children are largely associated with the ST59-MRSA-Ⅳ (t437) and ST239-MRSA-Ⅲ (t037) clones.These two may belong to communityacquired MRSA and hospital-acquired ones, respectively. Different prevalent clones were detected in different diseases and different regions. Therefore,there is a need to conduct further research on clinical isolates,which can guide the choice of antibiotic treatment and the examination of MRSA prevalence.