ABSTRACT
Objective To understand the antimicrobial susceptibility profiles,serotype distribution and virulence genes.Methods A total of 515 group B Streptococcus (GBS) including 108 virulence,112 non virulence,and 295 colonizing isolates were collected in four Shenzhen hospitals.Isolates were characterized by conventional and molecular serotyping.The virulence genes of scpB,lmb,hylB,cylE,bac,bca and rib of GBS isolates were detected by PCR.Antimicrobial susceptibility to penicillins,macrolides,lincosamides,quinolones and tetracyclines was tested using disk diffusion and the MICs for penicillin were determined by E test.Results Molecular serotyping for all eight serotypes (Ⅰa,Ⅰb,Ⅱ ～ Ⅵ,Ⅸ) was in full accordance with conventional serotyping.Taking MS and CS together,serotype Ⅲ was the most common capsular type (56.5 ％),followed by Ⅰb (17.5 ％),Ⅰa (12.6 ％),V (7.4 ％),Ⅱ (2.7 ％),Ⅵ (1.4 ％),Ⅳ (1.0 ％) and Ⅸ (1.0 ％).Serotype Ⅲ was the main serotype in different groups,serotype Ⅰ a was significantly more common among patients with invasive infections (11.1％) and no invasive infections (29.5％),serotype Ⅰb isolates were significantly more common among clone (19.3％).Virulence gene screening using PCR method showed the presence of cylE,lmb,scpB and hylB in almost all the isolates,while rib,bca and bac genes were found in 29.1％,14.6％ and 9.7％ of the isolates.Certain genes were significantly associated with specific serotypes,for example,rib with serotypes Ⅲ,Ⅰa and Ⅰb,bca and bac with serotypes Ⅲ and Ⅰb.Drug susceptibility results showed that GBS susceptibility to β lactam antimicrobials was prevalent (100 ％).Resistance rates for erythromycin,clindamycin and tetracycline were 67.0 ％,61.9 ％ and 86.0 ％,respectively.Conclusion Serotype distribution,virulence genes and antimicrobial susceptibility profiles of GBS contributes to the clinical therapy,epidemiological studies and design of Vaccines.