Bovine mastitis is the most common infectious disease in dairy herds and causes important economic losses. Various pathogens can cause the disease, with Staphylococcus aureus being one of the most significant. S. aureus can cause clinical, subclinical, and chronic forms of the disease due to a variety of virulence factors, including protein A, coagulase, toxins, and adhesins. The presence of methicillin-resistant S. aureus strains complicates treatment protocols and raises concerns about antimicrobial resistance. The genetic characterization of these strains, utilizing techniques such as molecular typing by pulsed-field gel electrophoresis (PFGE), reveals the existence of different genetic and virulence profiles, as well as the geographical variations in the distribution of these genotypes. The role of next-generation sequencing (NGS) technologies, functional genomics, and multi-omics approaches in the genetic research of bovine mastitis are highlighted, providing a complete understanding of its genetic basis and opening opportunities for targeted interventions and improved disease control strategies in the dairy industry. This review highlights the importance of understanding the genetic diversity and pathogenic mechanisms of S. aureus in bovine mastitis to develop effective disease management strategies and reduce economic losses in the dairy sector globally.

Streptococcus uberis is a bovine mastitis pathogen with a demonstrated ability to form biofilms. However, the dynamics of this process remain poorly characterized. This study aimed to comprehensively characterize biofilm formation in four S. uberis strains that differed in their biofilm-forming capacity, from weak to strong producers, and in the presence of key virulence-associated genes, such as sua, hasA and hasC. To achieve this, we integrated structural, biochemical, physiological and transcriptional analyses using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), spectral flow cytometry and qRT-PCR. The multi-faceted analysis revealed a coordinated maturation peak at 48 h, characterized by a structured architecture with water channels, a distinct biochemical signature rich in polysaccharides and proteins, and a predominantly viable bacterial population. This peak coincided with a marked upregulation of key virulence-associated genes, with sua expression increasing 2.5-fold and hasA increasing 3-fold at 48 h. This mature biofilm conferred high tolerance to antibiotics, with eradication concentrations (>256 µg/mL) exceeding planktonic MICs, although tetracycline was notably effective. At 72 h, the biofilm entered a dispersion phase characterized by structural collapse and reduced viability. These findings establish S. uberis biofilm maturation as a highly coordinated process, providing new insights into the biofilm lifecycle of this important pathogen and identifying key temporal and molecular targets for future interventions.

Enterococcus lactis is increasingly recognized as an emerging mastitis pathogen, yet the functional basis of its virulence and associated health risks remain poorly defined. This study presents an integrated genomic and phenotypic characterization of E. lactis strain EL-A150 isolated from bovine subclinical mastitis. Whole-genome sequencing revealed a 2.49 Mb circular chromosome encoding multiple genes associated with adhesion (acm, bepA, fms, sagA), biofilm formation (empB, empC) and antimicrobial resistance, including determinants related to aminoglycosides and macrolides. Phenotypic assays demonstrated rapid growth, strong biofilm-forming capacity and high adhesion to bovine mammary epithelial cells, while internalization remained low and intracellular persistence was transient. Comparative genomic analyses confirmed the taxonomic placement of the strain within the E. lactis clade (ANI up to 99.5% against reference genomes) and revealed a limited resistome composed of chromosomally encoded genes, with no detectable plasmids or major mobile genetic elements. Collectively, these findings demonstrate that E. lactis EL-A150 possesses a coordinated set of traits conducive to intramammary colonization, supporting its classification as an opportunistic pathogen. The convergence of virulence potential and clinically relevant antimicrobial resistance within a single isolate underscores a One Health concern and highlights the need for surveillance frameworks that integrate functional validation with genomic risk assessment.