Thermotolerant Campylobacters are one of the most important bacterial causative agents of human gastrointestinal illness worldwide. In most European Union (EU) member states human campylobacteriosis is mainly caused by infection with Campylobacter jejuni or Campylobacter coli following consumption or inadequate handling of Campylobactercontaminated poultry meat. To date, no effective strategy to control Campylobacter colonization of broilers during rearing is available. In this review, we describe the public health problem posed by Campylobacter presence in broilers and list and critically review all currently known measures that have been researched to lower the numbers of Campylobacter bacteria in broilers during rearing. We also discuss the most promising measures and which measures should be investigated further. We end this review by elaborating on readily usable measures to lower Campylobacter introduction and Campylobacter numbers in a broiler flock.

Thermotolerant Campylobacter spp., specifically Campylobacter jejuni and Campylobacter coli, are the most common bacterial causes of human gastroenteritis in developed countries. Consumption of improperly prepared poultry products and cross contamination are among the main causes of human campylobacteriosis. The aim of this study was to identify lactic acid bacterial (LAB) strains capable of inhibiting C. jejuni growth in initial in vitro trials ('spot-on-lawn' method), as well as in batch fermentation studies mimicking the broiler caecal environment. These experiments served as an indication for using these strains to decrease the capability of Campylobacter to colonise and grow in the chicken caeca during primary production, with the aim of reducing the number of human campylobacteriosis cases. A total of 1,150 LAB strains were screened for anti-Campylobacter activity. Six strains were selected: members of the species Lactobacillus reuteri, Lactobacillus agilis, Lactobacillus helveticus, Lactobacillus salivarius, Enterococcus faecalis and Enterococcus faecium. After treatment with catalase, proteinase K and a-chymotrypsin, anti-Campylobacter activity of cell-free culture supernatant fluid (CSF) for all six strains was retained, which indicated that activity was probably not exerted by bacteriocin production. Based on the activity found in CSF, the compounds produced by the selected strains are secreted and do not require presence of live bacterial producer cells for activity. During initial in vitro fermentation experiments, the E. faecalis strain exhibited the highest inhibitory activity for C. jejuni and was selected for further fermentation experiments. In these experiments we tested for therapeutic or protective effects of the E. faecalis strain against C. jejuni MB 4185 infection under simulated broiler caecal growth conditions. The best inhibition results were obtained when E. faecalis was inoculated before the C. jejuni strain, lowering C. jejuni counts at least one log compared to a positive control. This effect was already observed 6 h after C. jejuni inoculation.

Bacterial gastroenteritis caused by thermotolerant Campylobacter species, mainly Campylobacter jejuni, has been the most reported zoonotic disease in many developed countries in recent years. Reducing Campylobacter shedding on the farm could result in a reduction of the number of campylobacteriosis cases. In 2 independent broiler seeder experiments, in which broiler chickens were orally inoculated with 2 amounts of Enterococcus faecalis MB 5259, we established whether a live E. faecalis strain was capable of reducing cecal Campylobacter colonization in broiler chickens. In previous in vitro experiments it has been demonstrated that this E. faecalis MB 5259 displays anti-Campylobacter activity. The effect of pH and bile salts on E. faecalis MB 5259 showed that growth and survival of E. faecalis MB 5259 can be impaired during passage through the gastrointestinal tract of broiler chickens. Despite these results E. faecalis MB 5259 was capable of colonizing the broiler ceca. Contrary to the in vitro experiments, in which E. faecalis MB 5259 inhibited C. jejuni MB 4185 growth, no inhibition was observed in the in vivo experiments independent of the inoculum size.

Reducing Campylobacter shedding on the farm could result in a reduction of the number of human campylobacteriosis cases. In this study, we first investigated if allicin, allyl disulfide, and garlic oil extract were able to either prevent C. jejuni growth or kill C. jejuni in vitro. Allyl disulfide and garlic oil extract reduced C. jejuni numbers in vitro below a detectable level at a concentration of 50 mg/kg (no lower concentrations were tested), whereas allicin reduced C. jejuni numbers below a detectable level at a concentration as low as 7.5 mg/kg. In further experiments we screened for the anti-C. jejuni activity of allicin in a fermentation system closely mimicking the broiler cecal environment using cecal microbiota and mucus isolated from C. jejuni-free broilers. During these fermentation experiments, allicin reduced C. jejuni numbers below a detectable level after 24 h at a concentration of 50 mg/kg. In contrast, 25 mg/kg of allicin killed C. jejuni in the first 28 h of incubation, but anti-C. jejuni activity was lost after 48 h of incubation, probably due to the presence of mucin in the growth medium. This had been confirmed in fermentation experiments in the presence of broiler cecal mucus. Based on these results, we performed an in vivo experiment to assess the prevention or reduction of cecal C. jejuni colonization in broiler chickens when allicin was added to drinking water. We demonstrated that allicin in drinking water did not have a statistically significant effect on cecal C. jejuni colonization in broilers. It was assumed, based on in vitro experiments, that the activity of allicin was thwarted by the presence of mucin-containing mucus. Despite promising in vitro results, allicin was not capable of statistically influencing C. jejuni colonization in a broiler flock, although a trend toward lower cecal C. jejuni numbers in allicin-treated broilers was observed.

In this study, we characterized 272 Shiga toxin-producing Escherichia coli (STEC) isolates from humans, food, and cattle in Belgium [O157 (n = 205), O26 (n = 31), O103 (n = 15), O111 (n = 10), O145 (n = 11)] for their virulence profile, whole genome variations and relationships on different genetic levels. Isolates of O157 displayed a wide variation of stx genotypes, heterogeneously distributed among pulsogroups (80% similarity), but with a concordance at the pulsosubgroup level (90% similarity). Of all serogroups evaluated, the presence of eae was conserved, whereas genes encoded on the large plasmid (ehx, espP, katP) occurred in variable combinations in O26, O103, and O145. The odds of having haemolytic uraemic syndrome was less for all genotypes stx2a, stx2c, stx1/stx2c, and stx1 compared to genotype stx2a/stx2c; and for patients aged >5 years compared to patients aged ≤ 5 years. Based on the genetic typing and by using epidemiological data, we could confirm outbreak isolates and suggest epidemiological relationships between some sporadic cases. Undistinguishable pulsotypes or clones with minor genotypic variations were found in humans, food, and cattle in different years, which demonstrated the important role of cattle as a reservoir of STEC O157, and the circulation and persistence of pathogenic clones.