Escherichia coli strains producing selected bacteriocins inhibit porcine enterotoxigenic Escherichia coli (ETEC) both under in vitro and in vivo conditions.

Enterotoxigenic Escherichia coli (ETEC) and Shiga toxin-producing E. coli (STEC) strains are the causative agents of severe foodborne diseases in both humans and animals. In this study, porcine pathogenic E. coli strains (n = 277) as well as porcine commensal strains (n = 188) were tested for their susceptibility to 34 bacteriocin monoproducers to identify the most suitable bacteriocin types inhibiting porcine pathogens. Under in vitro condition, the set of pathogenic E. coli was found to be significantly more susceptible to a majority of tested bacteriocins when compared to commensal E. coli Based on production of bacteriocins with specific activity against pathogen, three potentially probiotic commensal E. coli strains of human origin were selected. These strains were found to be able to outcompete ETEC strains expressing F4 or F18 fimbriae in liquid culture and also decrease severity and duration of diarrhea in piglets during experimental ETEC infection as well as pathogen numbers in the last day of in vivo experimentation. While the extent of the probiotic effect was different for each strain, the cocktail of all three strains showed the most pronounced beneficial effects suggesting synergy between tested E. coli strains.ImportanceIncreasing level of antibiotic resistance among bacteria increases also the need for alternatives to conventional antibiotic treatment. Pathogenic Escherichia coli represents a major diarrheic infection agent of piglets in their postweaning period, however, available measures to control the infections are limited. This study describes three novel E. coli strains producing antimicrobial compounds (bacteriocins) which actively inhibit a majority of toxigenic E. coli strains. Beneficial effect of three potentially probiotic E. coli strains was demonstrated both under in vitro and in vivo conditions. The novel probiotic candidates may be used as prophylaxis during piglets' postweaning period to overcome common infections caused by E. coli.