Antimicrobial resistance landscape of Streptococcus agalactiae isolates in sub- Saharan Africa: a systematic review and meta-analysis of prevalence

Abstract

Background: Streptococcus agalactiae (Group B Streptococcus, GBS) represents a major public health concern in sub-Saharan Africa due to its role in invasive neonatal infections. This systematic review and meta-analysis aimed to estimate the pooled prevalence of maternal GBS colonization between 2013 and 2025, and to describe the distribution of capsular serotypes and antimicrobial resistance profiles. Methods: In accordance with PRISMA 2020 guidelines (PROSPERO: CRD420261289510), a comprehensive search was conducted across PubMed/MEDLINE, Scopus, Web of Science, Google Scholar, and AJOL. A total of 742 records were identified, of which 24 observational studies met the inclusion criteria. The methodological quality of the included studies was generally moderate to high, with a low to moderate risk of bias. Results: The pooled prevalence of maternal GBS carriage was estimated at 20–25%, with substantial inter-study heterogeneity. Serotype III predominated (≈32%), followed by serotypes Ia and V, reflecting global epidemiological trends and the predominance of hypervirulent lineages such as CC17. β-lactams retained excellent efficacy (resistance <3%), supporting their continued use as first-line agents for intrapartum antibiotic prophylaxis. In contrast, high resistance rates were observed for tetracycline (~88%), erythromycin (~35%), and clindamycin (~30%), largely associated with the high prevalence of resistance genes such as tetM, erm, and mef. Variability in sampling methods and the limited use of molecular tools may have influenced the detection of hypervirulent clones and resistance determinants. Conclusion: GBS remains a major public health issue in sub-Saharan Africa. The high prevalence of maternal carriage, coupled with rising antimicrobial resistance and the predominance of invasive serotypes, highlights the urgent need to strengthen microbiological surveillance and to accelerate the development and implementation of maternal vaccination strategies.