新生儿金黄色葡萄球菌临床分离株分子分型及毒力基因研究

Molecular and virulence characteristics of Staphylococcus aureus isolated from neonates

目的明确新生儿金黄色葡萄球菌(Staphylococcus aureus,SA)临床分离株的分子分型及毒力基因的携带特点。方法 2013年1月—2019年10月从北京儿童医院共收集到189株新生儿SA临床分离株,对所有菌株进行多位点序列分型(multilocus sequence typing , MLST)、葡萄球菌染色体盒(staphylococcal cassette chromosomemec, SCCmec)分型、金黄色葡萄球菌蛋白A(Staphylococcus protein A, Spa)分型,并进行了杀白细胞毒素(Panton-valentine leucocidin, PVL)基因及21种超抗原毒力基因的检测。结果 189株SA临床分离株中,125株分离自呼吸道分泌物标本,55株分离自皮肤软组织感染的脓液,8株分离自血液,1株分离自胸腔积液。189株SA中有98株甲氧西林敏感SA(methicillin-susceptible SA,MSSA)及91株甲氧西林耐药SA(methicillin-resistant SA,MRSA)。MSSA克隆型较分散,共发现了42种克隆型,ST188-t189是主要的克隆型,占11%;MRSA共有26种克隆型,ST59-SCCmecⅣa -t437为主要的克隆型,占53%。MRSA中PVL的阳性率(32%)明显高于MSSA(10%)(P<0.01),有166株菌株(88%)至少携带一种超抗原毒素基因,其中携带率最高的为肠毒素基因seq和seb,分别为47%和43%,seb-sek-seq是最常见的超抗原基因谱型。MRSA、MSSA菌株超抗原基因携带率分别为85%(77/91)和90%(88/98),两者间无明显差异。结论新生儿MRSA与MSSA的主要克隆型不同,MRSA的主要克隆型为ST59-SCCmecⅣa -t437,MSSA的主要克隆型为ST188-t189, MSSA的克隆型更为分散。MRSA中的PVL阳性率(32%)明显高于MSSA的PVL阳性率(10%),两者超抗原毒力基因携带率分别为85%和90%,无明显差异。

Objective To analyze the molecular and virulence characteristics of Staphylococcus aureus(S.aureus)isolated from neonates.Methods A total of 189 S.aureus isolates were collected from Beijing Children′s Hospital from January 2013 to October 2019 and analyzed by multilocus sequence typing(MLST),staphylococcal cassette chromosome mec(SCCmec)typing and Spa typing.Panton-valentine leucocidin(PVL)-encoding gene(pvl)and 21 superantigen virulence genes were also detected.Results The 189 S.aureus strains were isolated from respiratory secretions(n=125),pus(n=55),blood(n=8)and pleural effusion(n=1).There were 98 methicillin-susceptible S.aureus(MSSA)belonging to 42 MSSA clones and 91 methicillin-resistant S.aureus(MRSA)belonging to 26 MRSA clones.ST188-t189 and ST59-SCCmecⅣa-t437 were the predominant MSSA and MRSA clones accounting for 11%and 53%,respectively.The prevalence of pvl gene in MRSA isolates was significantly higher than that in MSSA isolates(32%vs 10%,P<0.01).There were 166 isolates(88%)carrying at least one superantigen virulence gene and among the 21 genes,seq and seb were the most common genes accounting for 47%and 43%,respectively.The most common superantigen genotype was seb-sek-seq.The positive rates of superantigen genes in MRSA and MSSA isolates were 85%(77/91)and 90%(88/98),respectively(P>0.05).Conclusions The main clones of MRSA and MSSA were different in neonates.ST59-SCCmecⅣa-t437 was the most predominant MRSA clone,while ST188-t189 was the most predominant MSSA clone.MSSA clones were more dispersed.The prevalence of pvl gene in MRSA was higher than that in MSSA.No significant difference in the prevalence of superantigen genes was observed between MRSA and MSSA.