<i>Lactobacillus reuteri</i> and <i>Enterococcus faecium</i> from Poultry Gut Reduce Mucin Adhesion and Biofilm Formation of Cephalosporin and Fluoroquinolone-Resistant <i>Salmonella enterica</i>

Non-typhoidal <i>Salmonella</i> (NTS) can cause infection in poultry, livestock, and humans. Although the use of antimicrobials as feed additives is prohibited, the previous indiscriminate use and poor regulatory oversight in some parts of the world have resulted in increased bacterial resistance to antimicrobials, including cephalosporins and fluoroquinolones, which are among the limited treatment options available against NTS. This study aimed to isolate potential probiotic lactic acid bacteria (LAB) strains from the poultry gut to inhibit fluoroquinolone and cephalosporin resistant MDR <i>Salmonella</i> Typhimurium and <i>S</i>. Enteritidis. The safety profile of the LAB isolates was evaluated for the hemolytic activity, DNase activity, and antibiotic resistance. Based on the safety results, three possible probiotic LAB candidates for in vitro <i>Salmonella</i> control were chosen. Candidate LAB isolates were identified by 16S rDNA sequencing as <i>Lactobacillus reuteri</i> PFS4, <i>Enterococcus faecium</i> PFS13, and <i>Enterococcus faecium</i> PFS14. These strains demonstrated a good tolerance to gastrointestinal-related stresses, including gastric acid, bile, lysozyme, and phenol. In addition, the isolates that were able to auto aggregate had the ability to co-aggregate with MDR <i>S.</i> Typhimurium and <i>S.</i> Enteritidis. Furthermore, LAB strains competitively reduced the adhesion of pathogens to porcine mucin Type III in co-culture studies. The probiotic combination of the selected LAB isolates inhibited the biofilm formation of <i>S.</i> Typhimurium FML15 and <i>S.</i> Enteritidis FML18 by 90% and 92%, respectively. In addition, the cell-free supernatant (CFS) of the LAB culture significantly reduced the growth of <i>Salmonella</i> in vitro. Thus, <i>L. reuteri</i> PFS4, <i>E. faecium</i> PFS13, and <i>E. faecium</i> PFS 14 are potential probiotics that could be used to control MDR <i>S</i>. Typhimurium and <i>S.</i> Enteritidis in poultry. Future investigations are required to elucidate the in vivo potential of these probiotic candidates as <i>Salmonella</i> control agents in poultry and animal feed.