Staphylococcus aureus in bovine intramammary infections: A global systematic review and meta-analysis of prevalence and antimicrobial resistance patterns

Background: Staphylococcus ( S. ) aureus is a globally pervasive and economically significant pathogen in bovine intramammary infections (IMIs) and is responsible for both clinical and subclinical mastitis. Objectives: This study systematically investigated the global epidemiology of S. aureus from bovine IMIs, addressing antimicrobial resistance (AMR) among S. aureus isolates through a meta-analysis. Methods: A total of 143 studies published between 2000 and 2025 were identified through comprehensive searches, which were based on predefined inclusion criteria. The data were systematically extracted, and the statistical analyses were performed in R (v4.5.2). Results: The meta-analysis included 143 studies (145,457 samples), with a pooled S. aureus prevalence of 24.78% and high heterogeneity (I 2  = 99.51%). Subgroup analyses demonstrated significant heterogeneity in prevalence by study design, publication year, and region, with greater heterogeneity in cross-sectional studies (I 2 >95%, p  < 0.001). Meta-regression identified sample size as a significant source of heterogeneity (β = −0.00002, p  = 0.02; R 2  = 3.41%). The highest prevalence was reported in Cameroon (67%), Sri Lanka (64.3%), Indonesia (57%), and India (44%), with the lowest prevalence reported in Poland (0.7%), Taiwan (2.0%), Australia (5.5%), and New Zealand (5.3%). AMR was highest for doxycycline (70.7%), penicillin (65.2%), and ampicillin (62.8%); moderate to oxacillin (44.6%) and vancomycin (40.2%); and lowest for gentamicin (27.5%) and amikacin (18.3%). Conclusion: S. aureus is highly prevalent in bovine IMIs worldwide, with marked regional heterogeneity and substantial resistance to commonly used antimicrobials, emphasizing the urgent need for targeted surveillance, prudent antimicrobial use, and improved mastitis control strategies at the global and regional levels.