Pathogen exclusion from intestinal mucus and antimicrobial susceptibility of Bifidobacterium spp. strains from fecal donors

Aim: To study the ability of bifidobacterial strains isolated from fecal donors to prevent pathogens from adhering to intestinal mucus, along with their antimicrobial susceptibility. Methods: Pathogen prevention was assessed through an in vitro adhesion assay using immobilized porcine mucus. Subsequently, bifidobacterial RNA-Seq data were analyzed to pinpoint glycoside hydrolases and glycosyltransferases possibly involved in mucus degradation affecting pathogen adhesion. The antimicrobial susceptibility of bifidobacterial strains was evaluated using in vitro susceptibility testing, followed by analysis of whole-genome sequencing data to reveal antimicrobial resistance genes. Results: Bifidobacterial strains inhibited pathogen adhesion to intestinal mucus, with most strains reducing the adhesion levels of pathogens like Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium, and Staphylococcus aureus by at least 70%. None of the strains significantly affected Pseudomonas aeruginosa, but they moderately reduced the adhesion of Yersinia enterocolitica. Gene expression analysis indicated that the more effective strains expressed higher levels of glycoside hydrolases, correlating with their pathogen exclusion capabilities. Antimicrobial susceptibility testing revealed that most strains were sensitive to several antibiotics, though some exhibited resistance to tobramycin, trimethoprim, and ciprofloxacin. Notably, one strain carried the tetW gene, conferring resistance to tetracycline. Conclusion: The bifidobacterial strains characterized in this study show potential for bacteriotherapeutic applications due to their strong ability to interfere with the adhesion of pathogenic bacteria and their lack of alarming antimicrobial resistance patterns.