Drug resistance, serotypes, virulence-associated genes and genotypes of infection or colonization of group B streptococcus in perinatal pregnant women

Abstract

Objective To study the characteristics of drug resistance, serotypes, virulence-associated genes and genotypes of infection or colonization of group B streptococcus(GBS)in perinatal pregnant women. Methods We collected 60 GBS strains which were isolated from cervix, vagina, blood and urine in perinatal pregnant women who were infected or colonized of GBS in Shenzhen People′s Hospital from January 2008 to October 2015. We preliminarily identified the GBS by Gram staining and cAMP test.The final identification of GBS strains was VITEK system.The drug resistance of GBS strains were detected by Kirby-Baue and E-test methods, Serotypes were performed by capsular serotyping.Multiplex polymerase chain reaction(PCR) was conducted to detect antimicrobial genes including ermA, ermC, ermB, mefAE and ermTR of erythromycin; linB gene of clindamycin; tetL, tetK, tetT, tetS, tetO and tetM genes of tetracycline; also main GBS virulence-associated genes of bac, bca, scpB, lmb and hylB.GBS genotypes were analyzed by multilocus sequence typing(MLST). Results ①All the 60 GBS strains were sensitive to penicillin and vancomycin. GBS strains resistance rate of tetracycline, erythromycin, clindamycin and levofloxacin were 88.3%, 70.0%, 43.3% and 35.0%, respectively.②The main serotypes of type Ⅰb, followed by type Ⅰa, type Ⅲ and type Ⅸ in GBS strains were 36.7%(22/60), 28.3%(17/60), 18.3%(11/60)and 10.0%(6/60). ③The main virulence-associated genes were hylB, lmb and scpB. 100.0%(60/60) GBS have hylB gene, 78.3%(47/60) GBS have lmb gene, 75.0%(45/60) GBS have scpB gene. ④The 60 GBS strains represented mainly genotypes were 30.0%(18/60) of ST19, 11.7%(7/60) of ST23, 8.3%(5/60) of ST12 and ST103 for each, and 6.7%(4/60) of ST485.Other genotypes were ST1, 4, 10, 17, 27, 28, 86, 199, 221, 325, 651, 653 and unknown types. Conclusions With the high antimicrobial resistance rates of erythromycin and clindamycin, they were not recommended for the treatment of perinatal pregnant women who were infected or colonized of GBS in Shenzhen People′s Hospital.The penicillin was still the most appropriate antibiotic for GBS treatment.For pregnant women who were allergic to penicillin, could choose vancomycin or levofloxacin based on patient′s clinical symptoms.In this study, the main serotypes of GBS of pregnant women were serotype Ⅰb and Ⅰa, representing virulence-associated genes of hylB, lmb and scpB, the main genotypes were ST19 and ST23. Key words: Streptococcus agalactiae; Serogroup; Drug resistance, bacterial; Virulence factors; Genotype; Multilocus sequence typing