Swine-Derived Probiotic Lactobacillus plantarum Inhibits Growth and Adhesion of Enterotoxigenic Escherichia coli and Mediates Host Defense

Abstract

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 <i>Escherichia coli</i> (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 <i>Lactobacillus plantarum</i> ZLP001 against ETEC infection were investigated by different methods. We found that bacterial culture and culture supernatant of <i>L. plantarum</i> 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 <i>L. plantarum</i> ZLP001. In addition, adhesion capacity of <i>L. plantarum</i> ZLP001 to IPEC-J2 cells were observed using microscopy and counting. <i>L. plantarum</i> 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 <i>L. plantarum</i> ZLP001 upregulated the expression of host defense peptides (HDPs) but did not trigger an inflammatory response. In addition, <i>L. plantarum</i> ZLP001 induced HDP secretion, which enhanced the potential antimicrobial activity of IPEC-J2 cell-culture supernatant after incubation with <i>L. plantarum</i> ZLP001. Our findings demonstrate that <i>L. plantarum</i> ZLP001, an intestinal <i>Lactobacillus</i> species associated with piglet health, possesses anti-ETEC activity. <i>L. plantarum</i> ZLP001 might prevent ETEC growth, inhibit ETEC adhesion to the intestinal mucosa, and activate the innate immune response to secret antimicrobial peptides. <i>L. plantarum</i> ZLP001 is worth investigation as a potential probiotics.