Abstract: Objective：To investigate the distribution characteristics of group B Streptococcus(GBS) serotypes isolated from pregnant women in Xi′an and the resistance spectrum of GBS to conventional antibiotics. Methods：A total of 498 GBS strains were collected from cultures of vaginal swabs of pregnant women in late pregnancy who received prenatal GBS screening in obstetrics department of Northwest Women′s and Children′s Hospital from January 2015 to December 2017． The serotype of GBS was determined by multiple PCR and the antibiotics sensitivity test and phenotype screening test were carried out. Results：All GBS isolates were sensitive to penicillin, ceftriaxone, vancomycin and linezolid. The resistance rates of GBS to erythromycin, clindamycin and levofloxacin were 76.7%, 73.5% and 58.0% respectively, and the resistance rate of erythromycin was increasing year by year. The predominant resistance phenotype was cMLSB(88.2%) among erythromycin-resistant strains, while iMLSB and M type strains accounted for only 5.5% and 6.3%. The most common serotypes were serotype Ⅲ, followed by Ⅰa, Ⅴ, type Ⅰb, Ⅱ and Ⅵ. Conclusions：(1) The vaginal colonization prevalence of GBS of pregnant women in Xi′an was similar to or slightly lower than that in other areas of China; (2) Six serotypes were identified with type Ⅲ being predominant; (3) The resistance rates of erythromycin, clindamycin and levofloxacin were higher than those of other areas, and the resistance rates of erythromycin were increasing year by year.

Key words: Streptococcus agalactiae, Pregnant women, Serotyping, Drug resistance, bacterial