Assessing Virulence Factor Genes in Pig-Derived Escherichia coli from the Region of Vojvodina Treated with Postbiotic Substance and Herbal Essential Oils

Antibiotic-resistant, biofilm-forming <i>Escherichia coli</i> may constitute a reservoir of antibiotic resistance and other determinants that can be transmitted to pathogenic bacteria for animals and humans. Therefore, it is crucial to reduce the incidence of these types of <i>E. coli</i>. The aim of this study was to determine whether essential oils from oregano, thyme, sage, and coriander, as well as the postbiotic substance PS412, can inhibit virulence factor genes possessing pig-derived <i>E. coli.</i> It aimed to find a new tool for the prevention and/or elimination of virulent <i>E. coli</i>. Altogether, 16 pig-derived <i>E. coli</i> from a pig farm in the region of Vojvodina (Serbia) were taxonomically identified using MALDI-TOF mass spectrometry; 14 strains (87.5%) with secure genus identification/probable species identification and 2 with highly probable genus identification. The <i>fimA</i> gene was detected in 62.5% of <i>E. coli</i> strains, and the <i>crl</i> gene in 87.5% of the strains. Ec3419/2 contained five analyzed genes. Five <i>E. coli</i> were found to form biofilm, as indicated by their growth on Congo red agar. The strains were mostly multi-resistant to antibiotics. Each <i>E. coli</i> strain produced the damaging enzyme, such as β-glucuronidase and/or α-chymotrypsin. However, they were susceptible to herbal essential oils (HEOs) with average inhibitory zones from 15 to 27 mm in diameter. They were also (6) susceptible to the PS412 (activity to 6400 AU/mL). The results contribute to the practical effectiveness of postbiotic substances, HEOs, and their combination as a novel approach to combating the virulence factors of <i>E. coli</i>. This insight also contributes to the strategy behind the One Health Concept.