Dissertation

Gut Feeling: Role of the Microbiome and Immune Response in Campylobacter Colonisation of the Chicken

Gilroy, Rachel Anne Jayne

2019

Overview

Campylobacter jejuni is the most frequent cause of bacterial foodborne gastroenteritis worldwide and is thought to affect ~ 600, 000 people in the UK each year alone. The preparation and consumption of poultry meat remains the single source of human Campylobacter infection. With over 60 % of UK retail chicken carcasses showing Campylobacter contamination, the poultry sector represents a crucial reservoir for human disease. Having been previously considered a commensal within avian species, infection biology of C. jejuni within the broiler chicken shows limited understanding. Despite numerous efforts to develop both on-farm and post-slaughter controls, these have all proven to be of limited efficacy. Therefore, an improved understanding of the infection biology of Campylobacter in the chicken and effective control methods are a priority Here we used in vivo experimental methods to develop our understanding of the complex infection dynamics and host-microbe interactions associated with prolonged Campylobacter infection within a commonly used broiler chicken breed. Sampled between 2 & 28 days post-infection (d.p.i), bacteriological analysis revealed rapid C. jejuni colonisation of the chicken gastrointestinal tract, persisting at a high burden within the caecal crypts once established. While infrequent, evidence of systemic spread of C. jejuni to liver and splenic tissues was observed in all experimental trials, further confirming the invasive ability within the chicken. Early C. jejuni colonisation was associated with early upregulation of pro-inflammatory and Th-17 immune mediators (IL-1β, IL-6, IL17A and CXCLi2) (p < 0.05) caecal and caecal tonsil tissue. Prolonged C. jejuni colonisation from 7 d.p.i onward was instead associated with regulatory immune mediators, IL-10 and TGFβ4 (p < 0.05). Modulation of the intestinal microbiome has been proposed as a potential control strategy for foodborne bacterial pathogens within poultry production, particularly as commercial chickens are reared in hatcheries with no maternal contact to develop an early or pioneer microbiome. We examined whether the at-hatch delivery of adult chicken caecal microflora (CMT) would lead to a more natural ‘avian’ microbiota which, in-turn, could drive an improvement in chicken gut health and reduce susceptibility to C. jejuni infection. Delivery of 0.1 - 0.2 ml CMT preparation (derived from 7-week old broiler chickens) within 4 hours post-hatch subsequently resulted in reduced within-flock transmission of C. jejuni and a reduced caecal C. jejuni burden (p < 0.05) following experimental infection compared to control birds. This response was consistently reproducible and sustained until commercial slaughter age. Compared to a commercial competitive exclusion microflora preparation (Aviguard® ), CMT administration was significantly more protective against C. jejuni colonisation of the caeca (p < 0.05). 16S rRNA Illumina MiSEQ analysis showed caecal content of birds treated with CMT had higher relative abundance of Firmicutestaxa – namely Ruminococcaceae (p < 0.05) compared to untreated control and Aviguard® treated birds. Caecal content of CMT treated chicks showed higher community richness compared to caecal content of both control (p < 0.001) and Aviguard® treated chicks (p < 0.001). These findings indicate that a novel, at-hatch transplantation of an adult chicken microbiota might prematurely drive successional development of the chick microbiota and reduce chicken susceptibility to experimental C. jejuni infection more effectively than a commercial competitive exclusion product.

• Publisher: ProQuest Dissertations & Theses
• Subject: Animal Diseases / Biology / Public health
• ISBN: 9798684620959