Abstract:

Abstract：Objective　To study the presence of virulence genes and associated mobile genetic elements in Staphylococcus aureus causing pediatric infections. Methods　A total of 109 Staphylococcus aureus strains collected between June 2005 and July 2009 were detected for the presence of 19 superantigen genes，2 exfoliative toxin genes and 3 adhesin genes by polymerase chain reaction. The distribution of virulence genes was analyzed between strains collected from different infections. Results　60 Staphylococcus aureus strains were isolated from children with pneumonia，49 from children with skin and soft tissue infections. Of the strains，90.8% harbored superantigen genes，with sek and seq as the most frequent genes （57.8%），followed by seb （45.9%） and sea （40.4%）. The sed and etd genes were not found in any of the strains tested. Thirty-seven superantigen genotypes were observed，of which the genotypes seb-sek-seq （ 20.2%） were the majority. About 78.4% （29/37） of the superantigen genotypes could be considered combinations of the superantigenic toxin gene-encoding profiles of mobile genetic elements. sek-seq without seb was found in 12 strains，Seb-seq without sek and seb-sek without seq was respectively found in 1 strain.10 of the tst-1-positive strains harbored seb. 4 of the sej-positive strains harbored ser.3 adhesin genes bbp、sdrE and cna were present in 91.7%、77.1%、30.3% of the strains，respectively. Seb，seq，bbp，sdrE were significantly associated with skin and soft tissue infections（P < 0.05）. Seg，sei，sen，seo and cna were significantly associated with pneumonia（P < 0.05）. Conclusion　The distribution of superantigen genes in Staphylococcus aureus isolated from children with pneumonia and skin and soft tissue infections implies the existence of new types or variants of mobile genetic elements in these strains. The frequencies of carriage of the 3 adhesin genes differ from other geographic areas. The roles of virulence genes in these two kinds of infections need further study.

Key words: staphylococcus aureus, pneumonia, skin and soft tissue infections, virulence gene, mobile genetic elements

摘要：

目的：研究儿童金黄色葡萄球菌（金葡菌）感染分离株中致病基因和相关可移动遗传元件的流行。方法　对2005年6月至2009年7月于北京、上海等国内8家医院收集到的109株金葡菌，通过聚合酶气边反应（PCR）方法检测19种超抗原基因、2种剥脱毒素基因和3种黏附基因，并比较致病基因在不同感染菌株中的分布。结果　60株金葡菌分离自肺炎患儿，49株分离自皮肤软组织感染患儿。90.8%的菌株携带超抗原基因，最常见的超抗原基因为sek（57.8%），seq（57.8%），其次为seb（45.9%），sea（40.4%）。未检测到sed和etd。发现了37种超抗原基因型，最常见的为seb-sek-seq（20.2%），78.4%的超抗原基因型可被认为是携带超抗原基因的可移动遗传元件组合。有12株菌携带sek-seq，但不携带seb，另有1株菌携带seb-seq但不携带sek，有1株携带seb-sek但不携带seq。在tst-1阳性的菌株中，有10株同时携带seb基因。在sej阳性的菌株中，有4株同时携带ser基因。3种黏附基因bbp、sdrE、cna分别存在于91.7%、77.1%、30.3%的菌株中。seb，seq，bbp，sdrE与皮肤软组织感染有显著相关性（P < 0.05），seg，sei，sen，seo，cna与肺炎有显著相关性（P < 0.05）。结论　引起儿童肺炎和皮肤软组织感染的金葡菌超抗原基因的分布特点提示，菌株可能携带新型可移动遗传元件或其变异体，3种黏附基因的携带率不同于其他地区，致病基因在肺炎及皮肤软组织感染中的作用尚需进一步研究。

关键词: 金黄色葡萄球菌, 肺炎, 皮肤软组织感染, 致病基因, 可移动遗传元件