Analysis of in vitro and in vivo effects of probiotics against Campylobacter spp

Campylobacter (C.) spp. are well recognised as the leading cause of bacterial food-borne diarrheal disease worldwide, with C. jejuni and C. coli as the most important species: C. coli is highly abundant in pigs and pork meat has often been implicated as a source for human infection. Intestinal colonisation of C. coli in pigs plays a role in carcass contamination during slaughter. Different pre-harvest intervention measures are proposed to reduce the C. coli burden in the porcine intestine. Among others, the use of probiotics to prevent or reduce the colonisation of intestinal pathogens is discussed. One aim of this study was to screen a variety of probiotics to evaluate their inhibitory activity against Campylobacter spp. in vitro. Therefore, cell-free culture supernatants of Lactobacillus spp., Bifidobacterium spp., Enterococcus (E.) faecium NCIMB 10415, and Escherichia coli Nissle 1917 were tested against C. jejuni and C. coli by a well-diffusion agar assay. Seven out of eleven Lactobacillus strains showed an inhibitory activity against at least one of the three tested Campylobacter strains. This antagonistic activity against Campylobacter spp. was caused by the production of organic acids that lowered the pH. Application with pH neutralised cell-free culture supernatants abolished this inhibitory effect. Other tested strains with probiotic properties showed no inhibitory activity against any Campylobacter spp. strain. The strain E. faecium NCIMB 10415 was chosen to test its inhibitory activity against C. coli in vivo. Twenty weaned piglets were allocated into two groups, a probiotic group and a control group.The diet of the probiotic group was supplemented with E. faecium NCIMB 10415 (10(9) cfu/kg feed, Cylactin) since weaning, whereas the control group received no probiotic treatment. All piglets were naturally colonised with C. coli. The excretion load of C. coli was monitored for 28 days. The results indicate that dietary supplementation of E. faecium NCIMB 10415 did not significantly affect C. coli excretion levels in pigs. In this study, E. faecium NCIMB 10415 showed no antagonistic activity against C. coli in vitro and in vivo and had no impact on the growth performance of weaned piglets.