Serotype distribution, antimicrobial resistance, and molecular characterization of group B Streptococcus isolates from Chinese pregnant woman

Abstract

Objective

This study was aimed to investigate the serotypes, antibiotic susceptibilities, and multi-locus sequence type (MLST) profiles of group B Streptococcus (GBS) in the Beijing area.

Methods

Lower vaginal and rectal swabs were obtained from pregnant women of 35–37 gestational weeks (GWs) who attended the Beijing Obstetrics and Gynecology Hospital. All GBS isolates were identified with Gram staining, catalase reaction assays, and CAMP tests, followed by antibiotic susceptibility testing, serotype identification, multilocus sequence typing and erythromycin resistance gene analysis (ermB and mefE).

Results

From July 2020 to June 2022, 311 (5.17%) of 6012 pregnant women that were screened for GBS colonization were detected positive. Of the eight serotypes identified (III, Ia, Ib, IV, II, VIII, V, and NT), serotypes III (43.09%), Ia (34.08%) and Ib (17.04%) were the predominant species. In the antimicrobial susceptibility experiments, the resistant rates measured for erythromycin, clindamycin, levofloxacin, and tetracycline were 76.21%, 63.99%, 50.80%, and 81.03%, respectively, and 7.6% of GBS isolates showed inducible clindamycin in resistance (D-test phenotype). Meanwhile, the multilocus sequence typing analysis showed that sequence type 19 (ST19) (30.34%) and ST10 (18.62%) were the dominant sequence types. Among the 237 erythromycin-resistant isolates, 176 harbored ermB (128, 54.00%) or mefE (48, 20.30%) gene alone.

Conclusion

The infection rates, serotypes or MSLT distribution, and antimicrobial resistance of GBS in Beijing area were investigated, which may be applied in analyses of the epidemiological characteristics of GBS. This contributes to the basic knowledge required for successful GBS vaccine development suited for disease prevention and treatment in China, as well as the implementation of effective clinical antimicrobials.

Keywords:

• GBS
• serotyping
• mLST
• susceptibility
• pregnancy

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Raw data were generated at Beijing Obstetrics and Gynecology Hospital, Capital Medical University. Derived data supporting the findings of this study are available from the corresponding author ZC and YZ on request.

Additional information

Funding

This work was supported by Beijing Health Technologies Promotion Program (BHTPP2022017), Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital ‘Discipline Backbone’ Plan Special Funds (XKGG201802) and Beijing Hospitals Authority Clinical Medicine Development of Special Funding Support (ZYLX202120). The funding body did not take part in the design of the study, the collection, analysis and interpretation of the data, or manuscript writing.