Intestinal colonization and acute immune response in commercial turkeys following inoculation with Campylobacter jejuni constructs encoding antibiotic-resistance markers

Authors: Sylte, Matthew; JOHNSON, TIMOTHY - Purdue University; MEYER, ELLA - Iowa State University; Inbody, Matt; Trachsel, Julian; Looft, Torey; LEONARDO, SUSTA - University Of Guelph; WU, ZUOWEI - Iowa State University; ZHANG, QIJING - Iowa State University

Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2019
Publication Date: 3/1/2019
Citation: Sylte, M.J., Johnson, T.A., Meyer, E.L., Inbody, M.H., Trachsel, J., Looft, T., Leonardo, S., Wu, Z., Zhang, Q. 2019. Intestinal colonization and acute immune response in commercial turkeys following inoculation with Campylobacter jejuni constructs encoding antibiotic-resistance markers. Veterinary Immunology and Immunopathology. 210:6-14. https://doi.org/10.1016/j.vetimm.2019.02.003.
DOI: https://doi.org/10.1016/j.vetimm.2019.02.003

Interpretive Summary: Campylobacter jejuni remains the main bacterial foodborne pathogen in humans. Ingestion of contaminated poultry products is the most common route by which humans are infected. Reducing the amount of Campylobacter in turkeys can lessen the amount of Campylobacter in retail turkey products and decrease human infection. In order to begin developing strategies to reduce the amount of Campylobacter in commercial turkeys, we must first understand the turkey’s immune response of Campylobacter. Turkeys were colonized with different Campylobacter jejuni. We discovered that different C. jejuni isolates colonize the intestine of starter and grower age commercial turkeys, but not all isolates colonize for the same amount of time. Campylobacter colonization induced a brief inflammatory immune response in the intestine that quickly resolved. Our results provide vital information for scientists to develop and test strategies that reduce the amount of Campylobacter in turkeys, which will promote a safe food supply and benefit consumers of retail turkey products.

Technical Abstract: Consumption of contaminated poultry products is one of the main sources of human campylobacteriosis, of which Campylobacter jejuni subsp. jejuni (C. jejuni) is responsible for approximately 90 percent of the cases. At slaughter, the ceca of commercial chickens and turkeys are the main anatomical site where C. jejuni asymptomatically colonizes. We have previously colonized commercial turkey poults with different isolates of C. jejuni and evaluated different media to best enumerate Campylobacter from intestinal samples, but the host-response is unknown in turkeys. Enumeration of Campylobacter (colony forming units (cfu)/gram of intestinal contents) can be challenging, and can be confounded if animals are colonized with multiple species of Campylobacter. In order to precisely enumerate the C. jejuni isolate used to experimentally colonize turkeys, constructs of C. jejuni (NCTC 11168) were tagged with different antibiotic resistance markers at the CmeF locus (chloramphenicol (CjCm) or kanamycin (CjK)). We sought to examine the kinetics of intestinal colonization using the antibiotic resistant constructs, and characterize the immune response in cecal tissue of turkeys. In vitro analysis of the tagged antibiotic-resistant constructs demonstrated no changes in motility, morphology, or adherence and invasion of INT-407 cells compared to the parent isolate NCTC 11168. Two animal experiments were completed to evaluate intestinal colonization by the constructs. In experiment 1, three-week old poults were colonized after oral gavage for 14 days, and CjCm and CjK cfu were recovered from cecal, but not ileal contents. In experiment 2, nine-week old poults were orally inoculated with CjCm, and the abundance of CjCm cfu/g of cecal contents significantly decreased beyond 14 days after inoculation. Significant lesions were detected in CjCm colonized poults at day 2 post-colonization. Using immunohistochemistry, Campylobacter antigen was detected in between cecal villi by day 7 of CjCm colonized poults. Quantitative RT-PCR of CjCm-colonized cecal tissue demonstrated significant down-regulation of IL-1b, IL-10 and IL-13 mRNA, and significant up-regulation of IL-6, IL-8, IL-17A, IL-22 and IFNg mRNA on day 2, and for some on day 7 post-colonization. All differentially expressed genes were similar to mock-infected poults by day 14. These data suggest that C. jejuni induced a brief inflammatory response in the cecum of poults that quickly resolved. Results from this study provide valuable insight into host-response and persistent colonization of the turkey cecum. These findings will help to develop and test strategies to promote food safety in commercial turkeys.