Cellular effect of lactic acid bacteria and their metabolites against animal production bacteria

Salmonella and Escherichia coli are major pathogens in animal production, and the growing ineffectiveness of conventional antibiotics is contributing to a public health crisis. One promising approach for bacterial control is the use of bioprotective lactic acid bacteria (LAB). This study aimed to evaluate the efficacy of six LAB, Pediococcus acidilactici PUCPR 011, P. acidilactici PUCPR 012, P. acidilactici PUCPR 014, Limosilactobacillus fermentum PUCPR 005, Lacticaseibacillus paracasei paracasei PUCPR 013, and Lacticaseibacillus rhamnosus PUCPR 010, and their cell-free supernatants (CFS) in inhibiting Salmonella and E. coli in intestinal cell cultures. The LAB strains demonstrated adhesion potentials ranging from 8.70±2.01% to 11.39±2.07%, while their CFS, at concentrations ≤11.25 g/L, did not negatively impact cell viability; in fact, they led to a significant increase in cell viability ( P < 0.05), which may result in either negative or positive effects. Further studies in the area are needed to deepen the understanding of these outcomes. CFS treatments resulted in a significant reduction in Salmonella adhesion, decreasing from 2.75±0.56% to between 0.80±0.23% and 0.91±0.24% ( P < 0.05). E. coli adhesion decreased from 1.66±0.50% to between 0.62±0.19% and 0.79±0.21% ( P < 0.05). When LAB were co-inoculated with the pathogens, Salmonella adhesion decreased from 2.95±0.42% to between 0.61±0.32% and 0.77±0.25% ( P < 0.05), and E. coli adhesion was reduced from 1.83±0.50% to between 0.47±0.16% and 0.68±0.20% ( P < 0.05). These findings suggest that the application of LAB or their CFS effectively inhibits pathogen adhesion, highlighting their potential as bioprotective agents.