Swine-Derived Probiotic Inhibits Growth and Adhesion of Enterotoxigenic and Mediates Host Defense.

Weaning stress renders piglets susceptible to pathogen infection, which leads to post-weaning diarrhea, a severe condition characterized by heavy diarrhea and mortality in piglets. Enterotoxigenic (ETEC) is one of typical strains associated with post-weaning diarrhea. Thus, prevention and inhibition of ETEC infection are of great concern. Probiotics possess anti-pathogenic activity and can counteract ETEC infection; however, their underlying mechanisms and modes of action have not yet been clarified. In the present study, the direct and indirect protective effects of ZLP001 against ETEC infection were investigated by different methods. We found that bacterial culture and culture supernatant of ZLP001 prevented ETEC growth by the Oxford cup method, and ETEC growth inhibition was observed in a co-culture assay as well. This effect was suggested to be caused mainly by antimicrobial metabolites produced by ZLP001. In addition, adhesion capacity of ZLP001 to IPEC-J2 cells were observed using microscopy and counting. ZLP001 also exhibited a concentration-dependent ability to inhibit ETEC adhesion to IPEC-J2 cells, which mainly occurred via exclusion and competition mode. Furthermore, quantitative real time polymerase chain reaction (qPCR) analysis showed that ZLP001 upregulated the expression of host defense peptides (HDPs) but did not trigger an inflammatory response. In addition, ZLP001 induced HDP secretion, which enhanced the potential antimicrobial activity of IPEC-J2 cell-culture supernatant after incubation with ZLP001. Our findings demonstrate that ZLP001, an intestinal species associated with piglet health, possesses anti-ETEC activity. ZLP001 might prevent ETEC growth, inhibit ETEC adhesion to the intestinal mucosa, and activate the innate immune response to secret antimicrobial peptides. ZLP001 is worth investigation as a potential probiotics.