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

## TL;DR

This study examines how herbal essential oils and a postbiotic substance can reduce virulence in antibiotic-resistant E. coli from pigs in Serbia.

## Contribution

The study introduces a novel approach using herbal essential oils and postbiotics to combat virulent E. coli.

## Key findings

- Herbal essential oils inhibited E. coli with average inhibitory zones of 15–27 mm.
- The postbiotic PS412 showed activity up to 6400 AU/mL against E. coli strains.
- Most E. coli strains were multi-resistant to antibiotics but susceptible to the tested natural substances.

## Abstract

Antibiotic-resistant, biofilm-forming Escherichia coli 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 E. coli. 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 E. coli. It aimed to find a new tool for the prevention and/or elimination of virulent E. coli. Altogether, 16 pig-derived E. coli 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 fimA gene was detected in 62.5% of E. coli strains, and the crl gene in 87.5% of the strains. Ec3419/2 contained five analyzed genes. Five E. coli were found to form biofilm, as indicated by their growth on Congo red agar. The strains were mostly multi-resistant to antibiotics. Each E. coli 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 E. coli. This insight also contributes to the strategy behind the One Health Concept.