Confronting bacterial mastitis: From pathogen diversity to sustainable control in the post-antibiotic era

Bacterial mastitis (BM) is a purulent inflammatory disease caused by a variety of pathogenic microorganisms, which is common in dairy cows, posing a major threat to animal husbandry. This article reviews the pathogenic bacteria classification, pathogenesis and treatment progress of BM. The main pathogens included Staphylococcus aureus (SA), Streptococcus agalactiae or group B Streptococcus (GBS), Escherichia coli ( E. coli ), Klebsiella pneumoniae ( K. pneumoniae ), coagulase-negative Staphylococcus (CoNS), Enterococcus and Streptococcus uberis ( S. uberis ). These bacteria cause infections through mechanisms such as adhesion, colonization, immune escape and drug resistance evolution. SA is internalized into host cells through fibronectin binding proteins (FnBPs), GBS relies on capsular polysaccharides (CPS) and C5a peptidases to evade immune clearance, and E. coli forms an intracellular niche through a non-classical endocytic pathway. At present, antibiotics are the main treatment, but the problem of drug resistance is prominent. Dry cow therapy (DCT) and post-milking teat dip (PMTD) can effectively prevent and control mastitis in dairy cows, while emerging therapies such as antimicrobial peptides (AMPs), nanotechnology, bacteriophage, and traditional Chinese medicine extracts (such as polysatin and geniposide) have shown alternative potential. In the future, it is necessary to combine multidisciplinary strategies to optimize pathogen-specific treatment regimens to meet the challenge of drug resistance and ensure public health safety. BM research not only needs to explore the pathogenic mechanism, but also needs to promote clinical transformation to achieve efficient prevention and control.