儿童社区获得性耐甲氧西林金黄色葡萄球菌肺炎分离株分子及临床特征

Molecular and clinical characteristics of community-acquired methicillin-resistant Staphylococcus aureus isolated from Chinese children with pneumonia

目的研究儿童社区获得性耐甲氧西林金黄色葡萄球菌(CA-MRSA)肺炎临床分离株的分子特征、耐药性及Panton-Valentine杀白细胞素(PVL)基因携带情况。方法 2006—2012年国内8家儿童医院在CA-MRSA肺炎患儿中分离出76株菌株;用PCR方法检测PVL基因;对所有菌株进行MLST、spa和SCCmec分型;采用琼脂稀释法进行14种抗生素的体外药物敏感试验。结果 76株CA-MRSA分离株中有32株(42.1%)携带PVL基因。在11种MLST型中,ST59(44.7%)是最主要的ST型;在17种spa型中,以t437(46.1%)为主;共有2种SCCmec型,以Ⅳ(82.9%)为主。CA-MRSA对红霉素和克林霉素的耐药率分别为86.9%和72.4%。PVL阳性菌株对庆大霉素的耐药率高于PVL阴性菌株,差异有统计学意义(53.1%比25.0%,P=0.012)。5例坏死性肺炎中4例分离株为PVL阳性T910-MRSA-Ⅳa-t318,1例为PVL阴性ST398-MRSA-Ⅴ-t034。结论 ST59-MRSA-Ⅳa-t437是儿童CA-MRSA肺炎分离株的主要流行克隆,未发现PVL与坏死性肺炎有相关性,但PVL阳性ST910-MRSA-Ⅳa-t318菌株与坏死性肺炎有关。CA-MRSA肺炎分离株对红霉素和克林霉素有较高的耐药性。

Objectives To investigate the molecular characteristics, antimicrobial resistance and prevalence of panton-valentine leukocidin （PVL）-positive community-acquired methicillin-resistant Staphylococcus aureus （CA-MRSA） isolated from children with pneumonia. Methods A total of 76 strains were isolated from children with CA-MRSA pneumonia admitted to 8 children＇s hospitals from 2006-2012 and analyzed by multilocus sequence typing （MLST）, spa typing, and staphylococcus cassette chromosome mec （SCCmec） typing. The PVL gene was also examined by PCR method. Susceptibility to 14 antimi- crobials was determined by using the agar dilution method. Results 42.1% of isolates were PVL-positive. Overall, 11 STs were identified and ST59 （44.7%） was the most prevalent type. 17 spa types were identified and t437 （46.1%） was predominant type. 2 SCCmec types were identified and IV （82.9%） was the most predominant type. The resistance rates of the isolates to erythromycin and clindamycin were 86.9% and 72.4%, respectively. The resistance rate of PVL positive isolates to gentamicin was higher than that of PVL negative isolates （53.1% vs 25.0%, P=0.012）. Four of five necrotic pneumonia isolates belonged to PVL positive T910- MRSA-IVa-t318 and one belonged to PVL negative ST398-MRSA-V-t034. Conclusions ST59-MRSA-IVa-t437 is the most prevalent CA-MRSA clone. Necrotic pneumonia is not related to PVL but related to PVL positive ST910-MRSA-IVa-t318. CA-MRSA isolates have high resistance to erythromycin and clindamycin.