Antimicrobial resistance patterns and polymicrobial co-detection characteristics of vaginal Group B Streptococcus in pregnant women: a retrospective study.

OBJECTIVE

This study aimed to describe antimicrobial resistance profiles, temporally proximate polymicrobial co-detection patterns, and clinical characteristics of Group B Streptococcus (GBS) in pregnant women, and to explore potential factors related to multidrug resistance (MDR) and pregnancy outcomes.

METHODS

A retrospective analysis was conducted on 508 pregnant women (gestational age ≥28 weeks) who underwent vaginal culture and antimicrobial susceptibility testing between January 2020 and December 2023 at a tertiary hospital in southern China. Pathogens were identified using the VITEK 2 system, and susceptibility testing was interpreted per CLSI 2023 criteria. Polymicrobial co-detection was operationally defined as the detection of ≥2 pathogens from the same anatomical site in the same specimen, on the same day, or within a predefined ±7-day interval. Clinical data and pregnancy outcomes were extracted from medical records.

RESULTS

GBS was detected in 23.6% (120/508) of participants. Based on the operational definition, 75.8% of GBS-positive women had temporally proximate detection of at least one additional pathogen, most commonly Candida albicans, Ureaplasma urealyticum, and Mycoplasma hominis. GBS isolates showed high susceptibility to penicillin (≥95%), whereas resistance to erythromycin (35.0%) and clindamycin (33.0%) was observed. Among isolates with complete susceptibility data, 9.0% (6/67) met the MDR definition. In exploratory analyses, gestational diabetes mellitus showed an elevated but imprecise association with MDR, while no robust evidence of association was observed for polymicrobial co-detection. Unadjusted comparisons indicated higher rates of cesarean delivery and premature rupture of membranes in GBS-positive women.

CONCLUSION

GBS colonization in pregnancy is frequently accompanied by temporally proximate detection of additional vaginal pathogens and macrolide/lincosamide resistance. MDR-related findings and clinical associations should be interpreted as exploratory and hypothesis-generating, and require confirmation in larger prospective studies.