Is allicin able to reduce Campylobacter jejuni colonization in broilers when added to drinking water?

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.