儿童社区获得性耐甲氧西林金黄色葡萄球菌感染研究

Study of community-acquired methicillin-resistant Staphylococcus aureus in children

目的探讨上海地区儿童社区获得性耐甲氧西林金黄色葡萄球菌(CA-MRSA)的流行状况、临床特征、耐药谱和分子学特征。方法总结2005年1月至2007年1月上海交通大学附属儿童医院收治社区发生MRSA感染的流行病学和临床资料,进行细菌耐药监测及分子学检测;分析本地区儿童CA-MRSA感染现状、发展趋势。结果在金黄色葡萄球菌感染患儿中MRSA检出率从7.5%增高至9.7%,其中CA-MRSA占MRSA的10.9%,而卫生保健相关性MRSA(HCA-MRSA)为65.2%。MRSA检出率有一定的季节分布。呼吸科和儿童重症监护病房的HCA-MRSA阳性最高(20%),CA-MRSA在外科较多(40%)。CA-MRSA皮肤软组织感染比例最高为40%,HCA-MRSA以肺炎和败血症为主(52%和36%)。HCA-MRSA危险因素主要是卫生保健机构接触和使用抗生素(64%),而医院获得性MRSA(HA-MRSA)以插管和机械通气为多见(4%)。30株MRSA mecA基因均为阳性。其基因型SCCmecⅡ型6株,SCCmecⅢ型15株,SCCmecⅣa型1株和SCCmecⅤ型2株,未能分型6株。PVL基因阳性11例,CA-MRSA均携带PVL基因。12株MRSA的spa基因中有3株(25.0%)完全相同。非多药耐药MRSA为17%,多药耐药MRSA对红霉素和克林霉素均达80%。结论上海地区儿童社区发生的MRSA感染增多,应引起儿科医师重视。儿童HCA-MRSA主要表现为呼吸道疾病和败血症;CA-MRSA除了可引起皮肤软组织感染外,也可引起重症肺炎和败血症。上海地区儿童MRSA菌株以SCCmec Ⅲ为主,CA-MRSA以SCCmecⅤ和未能分型株稍多。spa基因的多样性提示目前本地儿童MRSA并非流行株,需要作进一步连续耐药监测。

Objective To investigate the epidemiology, clinical status, antimicrobial resistance and molecular features of community-acquired methicillin-resistant Staphylococcus aureus （CA-MRSA） among children in Shanghai. Methods Data of patients with CA-MRSA infection admitted in Shanghai Children＇s Hospital Affiliated to Shanghai Jiaotong University between January 2005 and January 2007 were reviewed. A survey of etiology, clinical characteristics, prognosis, in vitro susceptibility test, and molecular features was done to analyze the current status and tendency of CA-MRSA infection. Results The MRSA infection increased from 7.5% to 9.7% during the period of study. CA-MRSA and health-care associated MRSA （HCA-MRSA） accounted for 11% and 65% of MRSA, respectively. The proportion of HCA-MRSA isolated from pulmonary wards and ICU was higher （20%） than that of other wards, while CA-MRSA was more common in the surgical department. CA-MRSA was more commonly found in skin and soft tissue infections （40%）, and HCA-MRSA was commonly associated with pneumonia （52%） and septicemia （36%）. Major risk factors for HCAMRSA infection were health care contact and previous antibiotic use （64%）, and risk factors for HA-MRSA were tracheal intubation and mechanical ventilation （12%）. All of the 30 MRSA isolates were mecA gene positive, 6 （20%） were SCCmec type Ⅱ , 15 （50%） were SCCmec type Ⅲ , 1 was SCCmec type Ⅳa, 2 were SCCmec typeV , 6 were untypeable. Eleven isolates were PVL gene positive, and all CA-MRSA carried PVL gene. Three （25%） of the MRSA strains shared the same spa gene. 17% （5 isolates） PVL-positive MRSA were non-muhidrug resistant. 80% muhidiug resistant MRSA were resistant to both erythromycin and clindamycin. Conclusions More attention should be paid on the increase of community-onset MRSA in children in Shanghai. HCA-MRSA was more likely to be invasive, while CA-MRSA could also cause severe pneumonia and septicemia beside skin and soft tissue infections. SCCmec type Ⅲ was the major type of MRSA in Shanghai. SCCmec type V and untypeable SCCmec were the more common types in CA-MRSA. The variety of spa genotypes in this study suggested that these isolates were not prevalent strains in Shanghai. More surveillance of antimicrobial resistance is needed.