Enterococcus spp., including E. faecalis and E. faecium, pose risks to dairy farms as opportunistic pathogens. The study evaluates antimicrobial resistance (AMR) and virulence characteristics of Enterococcus spp. isolated from bovine milk. Bile esculin agar was used to assess 1471 milk samples, followed by colony identification, gram staining, catalase tests, and 45 °C incubation. PCR analysis targeted E. faecalis and E. faecium in characteristic Enterococcus spp. colonies, with MALDI-TOF used for negative samples. Multiple tests, including disk diffusion, chromogenic VRE agar for vancomycin resistance, Vancomycin Etest^® for MIC determination, and PCR for virulence factors (cylA, esp, efaA, ace, asa1, gelE, and hyl genes), were performed. Out of 100 identified strains, E. durans (30.66%), E. faecium (26.28%), and E. faecalis (18.25%) were predominant. AMR in Enterococcus spp. varied, with the highest rates against rifampicin (27%), tetracycline (20%), and erythromycin (18%). Linezolid (5%), vancomycin, ciprofloxacin, and teicoplanin (3% each) had lower prevalence. E. faecium and E. faecalis showed high AMR to rifampicin, erythromycin, and tetracycline. Thirty-two strains (18.98%) grew on VRE Chromoselect agar, while 4 (2 E. faecalis and 2 E. faecium) showed vancomycin resistance by MIC values. E. faecalis carried gelE (45.5%) and asa1 (36%), and E. gallinarum had 9.1% with the asa1 gene. Detecting resistant Enterococcus in bovine milk supports control strategies for enterococci on dairy farms, highlighting AMR concerns in the food chain.

The inappropriate use of antimicrobials in dairy animals can lead to residues in raw milk and in dairy products. Foods containing residues of this nature, whether in the short, medium, or long term, cause serious health harm. Absence of these compounds in foods should be a premise for declaring safety. This systematic review aimed to identify the antibiotic residues most frequently found in raw bovine milk and the methodologies used to detect such residues over the ten years from 2013 to 2023. PRISMA guidelines for systematic reviews were followed, by searching the Web of Science, PubMed Central, Scopus, and Springer databases. The search strategy identified 248 articles, and after applying the selection and quality assessment criteria, 16 studies were selected. The number of samples analyzed was 411,530, of which 0.21% tested positive for some type of antibiotic. Eight classes and 38 different types of antibiotics were identified. The most common class was tetracycline, with emphasis on sulfonamides and quinolones, which have shown increasing prevalence among residues in milk in recent years. A total of 56.25% of the studies employed rapid kits to detect residues, 18.75% chromatography, and 25% both techniques. Antibiotic residues in bovine raw milk should be a great concern for animal, environmental, and human health.