Biofilm formation and antibiotic susceptibility pattern of Streptococcus agalactiae isolated from pregnant women in the City of Ramadi, Iraq

Background: Streptococcus agalactiae (Group B Streptococcus, GBS) is a significant opportunistic pathogen associated with adverse maternal and neonatal outcomes. The ability of GBS to form biofilms contributes to its persistence and resistance to antimicrobial treatment. This study aimed to investigate the prevalence of GBS colonization among pregnant women in late gestation (35–39 weeks), to evaluate the biofilm-forming capacity of the isolates, and to assess their antibiotic susceptibility profiles. Methods: A total of 200 vaginal swabs were collected from pregnant women. GBS isolates were identified and tested for biofilm formation using the microtiter plate assay with crystal violet staining. Antimicrobial susceptibility was evaluated using the Kirby–Bauer disc diffusion method on Mueller–Hinton agar. Results: GBS was isolated from 41% of samples. Among the isolates, 53.62% exhibited moderate biofilm formation, 37.68% weak, 7.25% strong, and 1.45% showed no biofilm formation. High resistance rates were observed to clindamycin (94%), penicillin (91%), ampicillin and erythromycin (88% each), cefazolin (81%), and levofloxacin (71%). Conclusion: The high prevalence of biofilm-forming GBS isolates and their alarming resistance to first-line antibiotics highlight a major clinical concern. The findings suggest limited efficacy of commonly prescribed antibiotics and indicate that levofloxacin may still provide therapeutic potential. Continuous monitoring of resistance patterns and consideration of alternative therapeutic strategies are crucial for managing GBS infections in pregnant women.