无乳链球菌的分子分型及耐药特征分析

Molecular characteristics and antibiotic susceptibility of clinical strains of Streptococcus agalactiae

目的了解北京一家三级医院临床分离无乳链球菌的血清型、耐药性、毒力基因的特征及多位点序列分型(MLST)特征。方法收集2018年一家医院住院患者分离到的无乳链球菌,通过聚合酶链式反应方法进行分子血清型分型和毒力基因检测,用MLST方法进行分子分型,通过VITEK 2药敏分析仪对菌株耐药性进行分析。结果该院2018年分离到31株无乳链球菌,MLST以序列分型(ST)10为主,占29.03%,其次为ST17、ST19、ST1、ST12、ST24和ST485,另有2株菌为新的ST;血清型分型以Ⅰb为主,占45.16%,其次为Ⅲ、Ⅴ及Ⅰa型。31株无乳链球菌中对氨苄西林、奎奴普汀、利奈唑胺和万古霉素全敏感,对四环素耐药率最高(64.52%),其次为左氧氟沙星(58.06%)和克林霉素(38.71%)。克林霉素耐药仅发现于Ⅰb和Ⅴ型。本研究的31株无乳链球菌,hylB、cylE、cfb和lmb毒力基因检测均为阳性;毒力基因bac和fbsA在不同分型中携带率有差异,其中bac及fbsA在Ⅰb型中携带率较高。结论本研究基于MLST分型和血清分型,表明不同型别间耐药性和毒力基因的差异,提示Ⅰb和Ⅴ型的耐药性及Ⅰb型的毒力需要引起关注。

Objective To understand the serotypes, antibiotic susceptibility, virulence gene carriage and multi locus sequence typing(MLST) results of clinical isolates of Streptococcus agalactiae in a class Ⅲ(A) hospital in Beijing. Methods S. agalactiae strains were isolated from the hospitalized patients in 2018. The serotyping, MLST and virulence gene detection were conducted by using polymerase chain reaction(PCR). The susceptibility test of S. agalactiae strains to 7 antibiotics was conducted with VITEK 2 system. Results A total of 31 strains of S. agalactiae were isolated in the hospital in 2018. In the sequence types(STs), ST10(29.03%) was predominant, followed by ST17, ST19, ST1, ST12, ST24, ST485 and 2 new types.In the 4 identified serotypes, Ⅰb was predominant, accounting for 45.16%, followed by Ⅲ, Ⅴ and Ⅰa. The antibiotic susceptibility test showed that 31 strains were all sensitive to ampicillin, quinupristin, linezolid and vancomycin. The highest resistance rate was 64.52% for tetracycline, followed by 58.06% for levofloxacin and 38.71% for 1 clindamycin. Clindamycin resistance was only found in the Ⅰb and Ⅴ serotype strains. PCR detection of virulence genes showed that all the strains were positive for hylB, cylE, cfb and lmb genes. The carriage of bac and fbsA genes varied in strains with different serotypes, and these virulence genes were carried in almost all the Ⅰb serotype strains. Conclusion Based on MLST and serotyping, our study showed that different types of S. agalactiae had different antibiotic resistance and varied different virulence genes,suggesting that close attention should be paid to the antibiotic resistance of Ⅰb and Ⅴ serotypes and virulence genes of Ⅰb serotypes of S. agalactiae.