Effects of exogenous protease supplementation of diets containing animal proteins or not on Campylobacter jejuni colonization and on the intestinal microbiota of broiler chickens.

BACKGROUND: Campylobacter jejuni, commonly present in the intestinal tract of poultry, is a major causative agent of human gastroenteritis. To successfully colonize the chicken gut, C. jejuni needs to have access to certain amino acids. However, the amino acid profile and its availability in the gut is dependent on the type of ingested protein and its digestibility. Therefore, manipulating the digestibility of different protein sources, using an exogenous protease, may be a promising way to control Campylobacter colonization in chickens. RESULTS: Chickens were fed with an exclusive vegetarian protein source diet (veggy diet) or a diet also containing animal proteins (animal diet), with or without exogenous protease from one day of age. At 14 days of age, all chickens were inoculated with two C. jejuni strains. At 7 days post infection (dpi) and 21 dpi, liver, ileal, and cecal contents were collected and used to enumerate C. jejuni by bacterial culture. Ileal and cecal contents were also used to analyze intestinal microbiota through 16S rRNA gene sequencing. The protease supplementation of the vegetarian protein source diet reduced cecal colonization levels of C. jejuni, increased its ileal amounts, and inhibited its hepatic dissemination. The addition of exogenous protease to the vegetarian protein source diet also altered alpha and beta diversities of the cecal microbiota but not of the ileal microbiota. The protease supplementation of the animal protein-based diet had no effect on Campylobacter colonization or on alpha diversity, unlike the beta diversity of the cecal content. Moreover, protease addition to the plant protein diet increased the cecal abundance of several genera such as UBA1819, Faecalibacterium, and Anaerostipes. In contrast, this supplementation decreased the cecal abundance of genera such as Tuzzerella, Monoglobus, and Fournierella. Using microbial co-occurrence networks, we observed that Campylobacter was positively linked to Negativibacillus in the vegetarian protein source diet group, while it was positively linked to Anaerotruncus and Tuzzerella and negatively linked to Faecalibacterium in the supplemented vegetarian protein diet group. CONCLUSIONS: Adding a commercially available protease to a vegetarian protein source diet appears to reduce C. jejuni colonization of the intestine, inhibit its translocation to the liver, and modify the cecal microbiota. These findings lead to further research questions on the interplay between C. jejuni strains, feed protein types, and commercial protease feed supplementation.