Temporal trends in Group B Streptococcus colonization, serotype distribution, and antimicrobial resistance among pregnant women in the Brazilian Amazon across the COVID-19 pandemic, 2018–2023

Group B Streptococcus (GBS) is a leading cause of preterm birth and neonatal infection. The COVID-19 pandemic substantially altered healthcare access, antibiotic use, and pathogen circulation. However, its influence on GBS remains poorly understood. This study evaluated temporal changes in GBS colonization, serotypes, and antimicrobial susceptibility among pregnant women in the Brazilian Amazon before, during, and after the COVID-19 pandemic. A total of 1,449 pregnant women at 35–37 weeks of gestation attending public health units in Porto Velho, Brazil, between February 2018 and November 2023 were included. Rectovaginal samples were cultured for GBS detection. Capsular serotyping and antimicrobial susceptibility testing were performed using standardized methods. Colonization prevalence, serotype distribution, and resistance profiles were compared across pre-pandemic, pandemic, and post-pandemic periods. Overall GBS colonization was detected in 20.7% (300/1,449) of participants, with variation across periods (22.6% before the pandemic, 21% during, and 19% after). Serotype Ia predominated (39%), followed by serotypes V (15.8%), II (14.1%), Ib (11.9%), III (10.2%), IV (5.1%), and VI (4%). Serotype distribution varied across periods without statistically significant differences. Non-susceptibility profiles differed significantly among serotypes. All isolates were susceptible to penicillin, ampicillin, cefazolin, and vancomycin. Increased non-susceptibility was observed for macrolides and levofloxacin, with multidrug-resistant (MDR) isolates rising from 5.7% to 15.9% post-pandemic. Together, these findings demonstrate temporal variation in GBS colonization, serotype distribution, and antimicrobial resistance across pre-, during-, and post-pandemic periods. While colonization, serotype distribution, and β-lactam susceptibility remained stable, significant increases in non-susceptibility to macrolides and levofloxacin, along with higher proportions of MDR profiles, were observed in later periods. These results highlight the importance of continued surveillance and provide relevant epidemiological insights to inform vaccine implementation and public health strategies in the post-pandemic era.