Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001
Performing Department
Veterinary Science
Non Technical Summary
Campylobacter species are the most common culture-proven cause of bacterial gastroenteritis worldwide, accounting for 400 - 500 million cases of diarrhea each year. Birds are a primary environmental reservoir for C. jejuni, and most human infections are a result of direct or indirect contact with contaminated poultry products. Specifically, 50 to 90% of domestic chicken carcasses are contaminated with C. jejuni at the time of sale. A fundamental goal of this proposal is to better understand how C. jejuni is able to intensively colonize poultry to levels especially dangerous to the food supply. Current strategies to reduce C. jejuni contamination of poultry have been largely unsuccessful, highlighting a gap in our understanding of how this bacterium establishes residence in the intestine.Intestinal bile plays an important role in digestion, absorption of fats, and the excretion of waste products, while concurrently providing a critical barrier against colonization by harmful bacteria, including C. jejuni. Previous work has demonstrated that the components of bile are toxic to bacterial cells. More specifically, the alteration in cellular membrane components results in elevated levels of reactive oxygen species (ROS) that cause DNA damage. Bacteria growing in the presence of ROS require DNA repair systems to maintain chromosomal integrity.We recently found that growing C. jejuni in conditions mimicking the host-gut environment (medium supplemented with a bile salt) resulted in the production of intracellular ROS, which in turn caused DNA damage. Our overarching hypothesis is that C. jejuni growth in the presence of the bile results in the generation of intracellular ROS, leading to certain mutations that provide C. jejuni with enhanced fitness. The experiments outlined in the proposed work will yield a global picture of the mutations produced due to C. jejuni exposure to bile. The results of this study will set the foundation for future studies directed towards dissecting the molecular mechanism(s) that C. jejuni utilizes to generate genomic mutations.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Campylobacter jejuni is responsible for millions of cases of diarrhea per year and is associated with Guillain-Barré syndrome, the leading cause of flaccid paralysis in the post-polio era. Chickens are a primary reservoir for C. jejuni, and most human infections are the result of direct or indirect contact with contaminated poultry products.The fundamental goal of this proposal is to gain a better understanding of C. jejuni growth and adaptation in the intestine of the natural animal host (chickens). Our working hypothesis is that host-induced DNA damage results in mutations that provide C. jejuni with enhanced in vivo fitness. It is critical to gain insight into the mechanisms C. jejuni utilizes to achieve a high level of chicken colonization (host adaptation) to develop strategies to mitigate the adaptive processes associated with human infections.
Project Methods
We will determine the mutations that occur in the genomes of C. jejuni strains in response to exposure to bile in culture and in the chicken. We have determined appropriate sample sizes by experimentation and power analysis to assure that the groups of chickens used will provide statistically significant data. Chicken colonization levels will be compared by a nonparametric Kruskal-Wallis test followed by Dunn's multiple comparisons test. Significant enrichment in DNA motifs or gene categories will be tested using Fisher's Exact test, and significance will be determined using Benjamini-Hochberg adjusted P-values. Statistical significance will be defined by a maximum value of multiplicity-adjusted P < 0.05 for all experiments.