Super- and low-shedding phenomena have been observed in genetically homogeneous hosts infected by a single bacterial strain. To decipher the mechanisms underlying these phenotypes, we conducted an experiment with chicks infected with Salmonella Enteritidis in a non-sterile isolator, which prevents bacterial transmission between animals while allowing the development of the gut microbiota. We investigated the impact of four commensal bacteria called Mix4, inoculated at hatching, on chicken systemic immune response and intestinal microbiota composition and functions, before and after Salmonella infection. Our results revealed that these phenotypes were not linked to changes in cell invasion capacity of bacteria during infection. Mix4 inoculation had both short- and long-term effects on immune response and microbiota and promoted the low-shedder phenotype. Kinetic analysis revealed that Mix4 activated immune response from day 4, which modified the microbiota on day 6. This change promotes a more fermentative microbiota, using the aromatic compounds degradation pathway, which inhibited Salmonella colonization by day 11 and beyond. In contrast, control animals exhibited a delayed TNF-driven pro-inflammatory response and developed a microbiota using anaerobic respiration, which facilitates Salmonella colonization and growth. This strategy offers promising opportunities to strengthen the barrier effect against Salmonella and possibly other pathogens.

• Keywords
• Salmonella, carrier-state, chicken, excretion, immune response, microbiota, super-shedder, virulence,
• MeSH
• Bacteria * immunology   classification   genetics   MeSH
• Chickens immunology   microbiology   MeSH
• Poultry Diseases * microbiology   immunology   prevention & control   MeSH
• Salmonella enteritidis * immunology   growth & development   physiology   MeSH
• Salmonella Infections, Animal * immunology   microbiology   prevention & control   MeSH
• Gastrointestinal Microbiome * immunology   MeSH
• Symbiosis MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH

Unlike in chickens, dynamics of the gut microbiome in turkeys is limitedly understood and no data were yet published in context of pathological changes following experimental infection. Thus, the impact of Histomonas meleagridis-associated inflammatory changes in the caecal microbiome, especially the Escherichia coli population and their caecal wall invasion in turkeys was investigated. Birds experimentally inoculated with attenuated and/or virulent H. meleagridis and non-inoculated negative controls were divided based on the severity of macroscopic caecal lesions. The high throughput amplicon sequencing of 16SrRNA showed that the species richness and diversity of microbial community significantly decreased in severely affected caeca. The relative abundances of operational taxonomic units belonging to Anaerotignum lactatifermentans, E. coli, and Faecalibacterium prausnitzii were higher and paralleled with a decreased abundances of those belonging to Alistipes putredinis, Streptococcus alactolyticus, Lactobacillus salivarius and Lactobacillus reuteri in birds with the highest lesion scores. Although the relative abundance of E. coli was higher, the absolute count was not affected by the severity of pathological lesions. Immunohistochemistry showed that E. coli was only present in the luminal content of caecum and did not penetrate even severely inflamed and necrotized caecal wall. Overall, it was demonstrated that the fundamental shift in caecal microbiota of turkeys infected with H. meleagridis was attributed to the pathology induced by the parasite, which only led to relative but not absolute changes in E. coli population. Furthermore, E. coli cells did not show tendency to penetrate the caecal tissue even when the intestinal mucosal barriers were severely compromised.

• Keywords
• Caecal microbiota, Escherichia coli, Histomonas meleagridis, Inflammation, Penetration, Turkeys,
• MeSH
• Escherichia coli physiology   MeSH
• Chickens * MeSH
• Poultry Diseases parasitology   MeSH
• Colony Count, Microbial veterinary   MeSH
• Protozoan Infections, Animal parasitology   MeSH
• Gastrointestinal Microbiome * MeSH
• Trichomonadida physiology   MeSH
• Typhlitis parasitology   veterinary   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH