A carvacrol-based product reduces Campylobacter jejuni load and alters microbiota composition in the caeca of chickens

Aim This study was conducted to test the ability of a carvacrol-based formulation (Phodé, France) to decrease the C. jejuni caecal load in inoculated broiler chickens and to study the impact of the C. jejuni inoculation alone or combined with the product, on the caecal microbiota. Methods and Results On day 1, chickens were either fed a control feed or the same diet supplemented with a carvacrol-based product. On day 21, the carvacrol-supplemented chickens and half of the non-supplemented chickens were inoculated with C. jejuni (108 CFU). Quantitative PCR was used to quantify C. jejuni in chicken caecal samples and 16S rRNA gene sequencing was carried out at 25, 31 and 35 days of age. A significant decrease of 1.4 log of the C. jejuni caecal load was observed in 35-day-old chickens supplemented with the product, compared to the inoculated and unsupplemented group (p < 0.05). The inoculation with C. jejuni significantly increased the population richness, Shannon and Simpson diversity and altered beta-diversity. Compared to the control group, the C. jejuni inoculation causes significant changes in the microbiota. The carvacrol-based product associated with C. jejuni inoculation increased the diversity and strongly modified the structure of the microbial community. Functional analysis by 16S rRNA gene-based predictions further revealed that the product up-regulated the pathways involved in the antimicrobial synthesis, which could explain its shaping effect on the caecal microbiota. Conclusions Our study confirmed the impairment of the caecal bacterial community after inoculation and demonstrated the ability of the product to reduce the C. jejuni load in chickens. Further investigations are needed to better understand the mode of action of this product to promote the installation of a beneficial microbiota to its host. Significance and Impact of the Study Results suggested that this product could be promising to control C. jejuni contamination of broilers.