摘要目的:分析儿童血液感染（BSI）金黄色葡萄球菌（SA）分离株的分子特征、毒力基因及耐药性，以进一步了解血流感染患儿分离SA的分子流行病学特征。方法:收集2016—2021年上海市儿童医院临床血流感染患者的53株SA，采用仪器法和纸片法检测细菌药物敏感性，采用聚合酶链反应技术检测SA的32种毒力基因；并进行多位点序列分型、葡萄球菌蛋白A（spa）分型及耐甲氧西林金黄色葡萄球菌（MRSA）菌株的葡萄球菌盒式染色体（SCCmec）分型。计数资料采用χ2检验或Fisher确切检验进行统计学分析。结果:53株SA菌株中，MRSA分离率达50.94%（27/53），ST398-t034-SCCmecⅤ（6/27，22.22%）和ST59-t437-SCCmecⅣ（4/27，14.81%）是MRSA分离株最常见的克隆型；甲氧西林敏感的金黄色葡萄球菌（MSSA）分离率达49.06%（26/53），以ST22-t309（3/26，11.54%）和ST7-t091/t1685（各2/26，7.69%）为流行分型。53株SA均携带≥6个毒力基因，33株菌株（62.26%）携带≥10个毒力基因，其中18株MSSA（69.23%）和15株MRSA（55.56%）， pvl基因在MSSA的携带率高于MRSA（12/26，33.33%比6/27，22.22%；χ2=3.382， P=0.065）， sasX仅在MRSA中检出（4/53，7.55%）。53株SA对青霉素、红霉素和克林霉素耐药率分别为98.11%、49.06%和41.51%，MRSA对常用抗菌药物的耐药率普遍高于MSSA。 结论:儿童血流感染MRSA分离率较高，ST398-t034和ST59-t437是其最常见的克隆型。儿童BSI-SA毒力基因携带率较高，毒力基因 pvl在MSSA中的携带率高于MRSA， sasX仅在MRSA中检出。儿童BSI-SA的耐药现状及毒力基因特征应引起临床重视。

abstractsObjectives:To study the molecular characteristics, virulence gene and resistance profiles of Staphylococcus aureus ( S. aureus, SA) isolates from bloodstream infections (BSI), so as to further understand the molecular characteristics of S. aureus in pediatric patients. Methods:A total of 53 S. aureus strains in bloodstream infections from Shanghai Children′s Hospital between 2016 and 2021 were collected. Antimicrobial susceptibility test were adopted by instrumental and disk diffusion method. Thirty-two kinds of virulence genes were detected by PCR and underwent multi-locus sequence typing (MLST), Staphylococcus protein A (spa) typing and staphylococcal chromosome cassette (staphylococcal cassette chromosome mec, SCCmec) typing characterizing methicillin-resistant Staphylococcus aureus (MRSA). Statistical analysis was performed using χ 2 test or Fisher exact test. Results:MRSA isolates accounted for 50.94% of the total(27/53), with ST398-t034-SCCmecV (6/53, 11.32%) and ST59-t437-SCCmecIV (4/53, 7.55%) as the most common MRSA clones. Methicillin-sensitive Staphylococcus aureus (MSSA) isolates occupied 49.06% (26/53), among which typing ST22-t309 (3/53, 5.66%) and ST7-t091/t1685 (2/53, 3.77% each) were prevalent. Of the 53 strains, all carried ≥6 virulence genes, 33 strains (62.26%) carried ≥10 virulence genes, including 18 strains of MSSA (69.23%) and 15 strains of MRSA (55.56%). The carriage rate of pvl gene in MSSA was higher than that of MRSA isolates (12/26, 33.33% vs. 6/27, 22.22%), and sasX was only detected in MRSA isolates (4/53, 7.55%). The resistant rates of BSI-SA isolates to penicillin, erythromycin and clindamycin were 98.11%, 49.06% and 41.51%, respectively. MRSA were more resistant to clinical antimicrobial agents than MSSA. Conclusions:MRSA strains cover a high proportion in S. aureus bloodstream infection of children, with ST398-t034 and ST59-t437 being the most common clones. The virulence gene carrying rate for BSI-SA was high with a greater pvl gene carrying rate in MSSA isolates while sasX was only detected in MRSA isolates. More clinical attention should be paid to the high resistance status and virulence genes characteristics of BSI-SA.