The Yin and Yang of Pathogens and Probiotics: Interplay Between Sv. Typhimurium and During Co-infection

Probiotic bacteria have been proposed as an alternative to antibiotics for the control of antimicrobial resistant enteric pathogens. The mechanistic details of this approach remain unclear, in part because pathogen reduction appears to be both strain and ecology dependent. Here we tested the ability of five probiotic strains, including some from common probiotic genera and , to reduce binding of sv. Typhimurium to epithelial cells subsp. emerged as a promising strain; however, Typhimurium infection outcome in epithelial cells was dependent on inoculation order, with unable to rescue host cells from preceding or concurrent infection. We further investigated the complex mechanisms underlying this interaction between , Typhimurium, and epithelial cells using a multi-omics approach that included gene expression and altered metabolism via metabolomics. Incubation with repressed apoptotic pathways and induced anti-inflammatory cascades in epithelial cells. In contrast, co-incubation with increased in Typhimurium the expression of virulence factors, induced anaerobic metabolism, and repressed components of arginine metabolism as well as altering the metabolic profile. Concurrent application of the probiotic and pathogen notably generated metabolic profiles more similar to that of the probiotic alone than to the pathogen, indicating a central role for metabolism in modulating probiotic-pathogen-host interactions. Together these data imply crosstalk via small molecules between the epithelial cells, pathogen and probiotic that consistently demonstrated unique molecular mechanisms specific probiotic/pathogen the individual associations.