The Strains Enterococcus faecalis as Contaminants of Raw Goat Milk and Their Treatment with Postbiotic Active Substances Produced by Autochthonous Lactococci

Enterococci from raw goat milk were taxonomically allotted in the species Enterococcus faecalis using sequencing (16S rRNA and BLASTn analysis) with a percentage identity up to 99.91%. The virulence factor gene gelE was found in the strains EE/K3, EE/G3, and EE/G6. The agg gene was detected in the strain EE/G6, and the esp gene was detected in the strains EE/K5 and EE/G7. Each strain possessed at least one virulence factor gene. In the strain EE/G6, the gelE and esp genes were found. The strains EE/G6 and EE/G3 showed resistance to tetracycline and vancomycin. EE/G7 was resistant to vancomycin and gentamicin. All strains possessed low-grade biofilm-forming ability (0.1 < A570 ≤ 1.0). They possessed genes for biofilm formation (bopD, srt, and/or ace). They also produced esterase (20–40 nmo/L), esterase lipase, and α-chymotrypsin (10–40 nmoL). The values of acid phosphatase reached 20–40 nmoL. The strains EE/G3, EE/G6, and EE/G7 were observed to possess the most pathogenicity. However, all strains were susceptible to postbiotic active substances produced by two autochthonous lactococci, MK2/8 and MK1/3 (inhibitory activity up to 400 AU/mL). These postbiotic substances provide a new potential alternative to reducing contaminants in milk.