In vitro evaluation of candidate probiotic bacteria against enterotoxigenic Escherichia coli (ETEC) isolated from post-weaning diarrhea in piglets.

Probiotics offer a promising alternative to antibiotics in animal husbandry. This study evaluated the inhibitory potential of live cells and cell-free supernatants (CFS) from 31 putative probiotic strains against two multidrug-resistant (MDR) enterotoxigenic Escherichia coli (ETEC) strains. Methods included antibiogram profiling, zone of inhibition assays, hemolytic activity, and auto-aggregation tests. Results highlighted strain-specific antimicrobial heterogeneity. Lactobacillus acidophilus ATCC 4356 and Pediococcus acidilactici CNCTC 6986 exhibited the strongest contact-dependent inhibition against SP11 and SP31, respectively, while Lactiplantibacillus plantarum FW0BV0887 displayed superior CFS-mediated activity. Notably, L. acidophilus ATCC 4356 and L. helveticus ATCC 15009 showed consistent efficacy in both assays. Safety assessments confirmed non-hemolytic phenotypes for most strains, excluding Enterococcus faecium. Furthermore, at the 24-h plateau, L. crispatus FB141-CAN-1 achieved the highest auto-aggregation capacity (88.03 ± 8.60%), followed closely by L. acidophilus ATCC 4356 (75.88 ± 2.62%), indicating putative adhesive potential. Overall, these findings identify specific probiotics with distinct antimicrobial mechanisms and preliminary safety profiles based on hemolytic activity, supporting their potential as biocontrol agents and warranting further in vivo validation.