# Bioprotective Effect of a Bacteriocin-Producing Lactococcus lactis Strain Against Enterococcus faecium Isolated from Egyptian Tallaga Cheese

## TL;DR

A Lactococcus lactis strain producing bacteriocins effectively inhibits harmful Enterococcus faecium in traditional Egyptian cheese.

## Contribution

Identification of Lactococcus lactis as a bioprotective agent against antimicrobial-resistant Enterococcus faecium in dairy products.

## Key findings

- Enterococcus faecium was found to dominate in Tallaga cheese, raising food safety concerns.
- Two Lactococcus lactis strains reduced E. faecium by up to 3.6 log units in a cheese model.
- Bacteriocin-producing L. lactis shows promise as a natural biopreservative in dairy.

## Abstract

Background/Objectives: Tallaga cheese is an artisanal form of traditional Egyptian soft white Damietta cheese, characterized by high moisture, elevated salinity, and a limited shelf life, which collectively increase its vulnerability to microbial contamination. Typically produced from raw or minimally heated cow or buffalo milk, Tallaga cheese represents a relevant model for studying emerging food safety challenges. Methods/Results: This study revealed marked variability among commercial samples and, unexpectedly, a general absence of typical lactic acid bacteria (LAB) such as Lactococcus spp. Instead, enterococci, microorganisms increasingly associated with antimicrobial resistance and virulence traits, emerged as the dominant LAB group, with the detection of Enterococcus faecium strains posing particular concern for dairy safety. To address these challenges, the antimicrobial potential of isolated LAB was evaluated against Latilactobacillus sakei (CECT 906). Twelve bacteriocin-producing strains were identified: ten Enterococcus faecalis, one E. faecium, and one Lactococcus lactis. Enterococci demonstrated robust tolerance to stress conditions, including high salt concentrations, emphasizing their persistence in dairy environments. Given the relevance of controlling resistant and potentially virulent strains such as E. faecium, the bioprotective capacity of two bacteriocinogenic L. lactis strains (IPLA 1064 and AHRI ST9) was assessed using a laboratory-scale cheese model. Both strains effectively inhibited E. faecium AHRI CH4, achieving reductions of 2.6 and 3.6 log units (99.9%). Conclusions: These findings underscore the relevance of bacteriocin-producing L. lactis as natural biopreservatives to mitigate emerging threats related to antimicrobial-resistant food-borne pathogens in dairy products.