Does Bovine Raw Milk Represent a Potential Risk for Vancomycin-Resistant Enterococci (VRE) Transmission to Humans?

<b>Background/Objectives</b>: Vancomycin-resistant enterococci (VRE) are significant nosocomial pathogens worldwide, potentially transmitted by food-producing animals and related products. This study investigates the epidemiological role of bovine raw milk in the transmission of VRE to humans. <b>Methods</b>: Bulk milk samples were screened for <i>van</i> gene presence using a multiplex PCR. Mastitogenic enterococci isolated from individual milk samples were tested for antimicrobial susceptibility using the broth microdilution method. Strains not susceptible to vancomycin were whole genome sequenced. <b>Results</b>: Overall, <i>vanC</i> genes were detected in 299/1026 (29.14%) bulk milk samples. Specifically, <i>vanC1</i> was found in 204 samples (19.88%) and <i>vanC2/3</i> in 57 samples (5.56%), with both detected simultaneously in 38 samples (3.70%). Clinically significant <i>vanA</i> and <i>vanB</i> genes were not identified. A total of 163 mastitogenic <i>Enterococcus</i> strains were isolated from individual milk samples. Eight different <i>Enterococcus</i> species were detected, with <i>E. faecium</i> (104/163, 63.80%) and <i>E. faecalis</i> (34/163, 20.86%) being the most common. Multidrug resistance was observed in 106/163 (65.03%) isolates. The most common resistance frequencies were to ciprofloxacin and erythromycin (102/163, 62.58% both), followed by quinupristin/dalfopristin (93/163, 57.06%), linezolid (65/163, 39.88%), tetracycline (58/163, 35.58%), daptomycin (46/163, 28.22%), chloramphenicol (33/163, 20.25%), ampicillin, tigecycline, and high-dosage gentamycin (8/163, 4.91% all). Resistance to teicoplanin was not observed. Two vancomycin non-susceptible strains were identified: one <i>vanC2/3 E. casseliflavus</i> and one <i>vanC1 E. gallinarum</i>. Whole genome sequencing confirmed the presence of the complete <i>vanC</i> gene cluster and several virulence genes in both strains. <b>Conclusions</b>: Our findings suggest that while raw milk is unlikely to be a source of vancomycin resistance genes of highest clinical importance (<i>vanA</i> or <i>vanB</i>), it may contribute to the spread of <i>vanC</i> enterococci, which are increasingly associated with human infections.