Prevalence and antimicrobial resistance of Streptococcus agalactiae associated with bovine mastitis in China: A meta-analysis

Background: A comprehensive understanding of the distribution of Streptococcus agalactiae, a major pathogen responsible for bovine mastitis, is critical for guiding therapeutic and control strategies. Aim: Thus, the objective of this meta-analysis is to investigate the prevalence and antimicrobial resistance (AMR) of S. agalactiae associated with bovine mastitis in China between 2004 and 2024. Methods: The relevant literature was retrieved from PubMed, Google Scholar, and the China National Knowledge Infrastructure database. Following the PRISMA guidelines, 33 studies were included in the final analysis, of which 14 reported AMR data. All analyses were performed using the STATA software. Results: The pooled S. agalactiae prevalence was 24%. Subgroup analyses revealed a higher prevalence in Central China, an upward trend over time (2019–2024 vs. before 2019), and a higher prevalence in clinical cases than in subclinical mastitis. The pooled AMR data indicated that sulfonamides had the highest resistance rates, followed by aminoglycosides, β-lactams, lincosamides, macrolides, tetracyclines, quinolones, and chloramphenicol. Conclusion: These findings highlight the need for continued surveillance and refinement of therapeutic protocols to effectively manage S. agalactiae-induced mastitis in Chinese dairy herds.