Evaluation of Probiotic Bacillus velezensis for the Control of Pathogens That Cause Post-Weaning Diarrhea in Piglets—Results from In Vitro Testing and an In Vivo Model Using Caenorhabditis elegans

We investigated the effect of probiotic <i>Bacillus velezensis</i> strains (LSSA01, 15AP4 and 2084) on pathogens causing post-weaning diarrhea in piglets (Enterotoxigenic <i>Escherichia coli</i>, <i>Clostridium perfringens</i>, <i>Salmonella</i> spp.). We studied the effect of <i>B. velezensis</i> and its cell-free supernatant on (1) pathogen growth; (2) IPEC-J2 cell cytokine and tight junction protein expression; (3) IPEC-J2 cell 'wound' recovery; (4) adhesion to IPEC-J2 cells and pathogen exclusion; and (5) <i>Caenorhabditis elegans</i> survival following pathogen exposure. Cell-free supernatant (CFS) from all strains inhibited the growth of ETEC F4 and F18 (by 36.9-53.2%; <i>p</i> < 0.05). One or more strains inhibited <i>C. perfringens</i> and <i>Salmonella</i> spp. (<i>p</i> < 0.05). Strain 2084 CFS increased IL-8 expression (+12.0% vs. control; <i>p</i> < 0.05; 6 h incubation), whereas LSSA01 CFS increased the expression of tight junction proteins (<i>p</i> < 0.05 vs. control; 6 h incubation) and accelerated 96 h 'wound' healing. Colony-forming units (CFUs) of all strains displayed a higher binding affinity to IPEC-J2 cells than 12 ETEC isolates, reduced adhesion of ETEC F4 and F18 and extended <i>C. elegans</i> survival over 30 d. The results indicate that probiotic <i>B. velezensis</i> strains have potential for use in the control of PWD pathogens.