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The acute host-response of turkeys colonized with Campylobacter coli

ABSTRACT: Consumption of contaminated poultry products is one of the main sources of human campylobacteriosis, of which Campylobacter jejuni subsp. jejuni (C. jejuni) and C. coli are responsible for approximately 98% of the cases. The ceca of commercial turkeys are the main anatomical site where Campylobacter asymptomatically colonizes. We have previously colonized the ceca of commercial turkey poults with C. jejuni, and demonstrated acute changes in cytokine gene expression in cecal tissue and histologically scored intestinal lesions at 2 days post-inoculation (dpi). The host-response of turkeys to C. coli colonization is unknown. Cecal tonsils (CT) are an important part of the gastrointestinal-associated lymphoid tissue that function to sample material passing in and out of the ceca and generating immune responses against intestinal pathogens. The CT immune response towards Campylobacter is unknown. In this study, we generated a C. coli kanamycin-resistant construct (CcK) for enumeration from cecal contents after experimental challenge. In vitro analysis of CcK demonstrated no changes in motility when compared to the parent isolate, but in vitro growth rates were significantly different than the parent strain. Poults were inoculated by oral gavage with CcK (5x10^7 cfu) or sterile-media (mock-colonized), and euthanized at 1 and 3 dpi. At both time points, CcK was recovered from cecal contents, but not from the mock-colonized group. As a marker of acute inflammation, serum alpha-1 acid glycoprotein was significantly elevated at 3 dpi in CcK inoculated poults compared to mock-infected samples. Significant histological lesions were detected in cecal and CT tissues of CcK colonized poults at 1 and 3 dpi, respectively. RNAseq analysis identified 250 differentially expressed genes (DEG) in CT from CcK colonized poults at 3 dpi, of which 194 were upregulated and 56 were downregulated. From the DEG, 9 significantly enriched biological pathways were identified, including platelet aggregation, response to oxidative stress and negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway. These data suggest that C. coli induced an acute inflammatory response in the intestinal tract of poults, and that platelet aggregation and oxidative stress in the CT may affect the turkey’s ability to resist Campylobacter colonization. Results from this study provide insight into host-response of the turkey CT to Campylobacter colonization. These findings will help to develop and test Campylobacter mitigation strategies to promote food safety in commercial turkeys.

ORGANISM(S): Meleagris gallopavo

PROVIDER: GSE158639 | GEO | 2020/10/01

REPOSITORIES: GEO

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Project description:Background: The food-borne pathogen Campylobacter is one of the most important zoonotic pathogens. Compared to other zoonotic bacteria, Campylobacter species are quite susceptible to environmental or technological stressors. This might be due to the lack of many stress response mechanisms described in other bacteria. Nevertheless, Campylobacter is able to survive in the environment and food products. Although some aspects of the heat stress response in Campylobacter (C.) jejuni are already known, information about the heat stress response in the related species C. coli and C. lari are still unknown. Results: The stress response to elevated temperatures (46°C) was investigated by survival assays and whole transcriptome analyses for the strain C. jejuni NCTC11168, C. coli RM2228 and C. lari RM2100. While C. jejuni showed highest thermotolerance followed by C. lari and C. coli, none of the strains survived at this temperature for more than 24 hours. Transcriptomic analyses revealed that only 3 % of the genes in C. jejuni and approx. 20 % of the genes of C. coli and C. lari were differentially expressed after heat stress, respectively. The transcriptomic profiles showed enhanced gene expression of several chaperones like dnaK, groES, groEL and clpB in all strains, but differences in the gene expression of transcriptional regulators like hspR, perR as well as for genes involved in metabolic pathways, translation processes and membrane components. However, the function of many of the differentially expressed gene is unknown so far. Conclusion: We could demonstrate differences in the ability to survive at elevated temperatures for C. jejuni, C. coli and C. lari and showed for the first time transcriptomic analyses of the heat stress response of C. coli and C. lari. Our data suggest that the heat stress response of C. coli and C. lari are more similar to each other compared to C. jejuni, even though on genetic level a higher homology exists between C. jejuni and C. coli. This indicates that stress response mechanisms described for C. jejuni might be unique for this species and not necessarily transferable to other Campylobacter species.

Project description:Campylobacter jejuni (C. jejuni) is a zoonotic pathogen that causes human diarrhea worldwide. Chickens are a natural reservoir of C. jejuni. Understanding the host response to C. jejuni infection at the molecular level will lay the foundation to control human campylobacterosis by reducing food contamination. Two distinct genetic lines, resistant (line A) and susceptible (line B) to C. jejuni colonization, were utilized to profile the host response to C. jejuni infection using an Agilent chicken 44K microarray. Day-old chickens were challenged orally with C. jejuni and spleens collected for total RNA 7 days post-challenge. Twenty infected samples with highest (a) or lowest bacterial number (b) in cecal content and twenty non-infected (c) in each line were randomly pooled into four biological replicates. The pair comparisons among these three groups within each line were analyzed. The signal intensity of each gene was normalized using LOWESS method. A mixed model was used to identify differentially expressed genes by SAS (P < 0.001). This was opposite to previous cecal tonsil microarray result. There were 468, 743, and 939 genes differentially expressed between groups a and c, groups a and b, and groups b and c in line A, respectively, and 201, 37, 126 genes in line B, respectively. More differentially expressed genes in spleen in line A than in line B were found. The results indicated that significantly different response to C. jejuni infection occurred between resistant and susceptible chicken lines, and the effects of interaction between genetics and tissue should be considered. Chickens in two broiler lines were inoculated with 10^5 cfu C. jejuni on one day after hatch. The cecal content and cecal tonsil was collected and bacterial number in cecal content was counted on day 7 after inoculation. Twenty samples were separated into 3 groups (high burden, low burden, and control) based on bacterial burden of cecal content in each line, 5 samples were mixed randomly into one pool. A dual color, balanced design was carried on for all samples. Three comparisons were used in each line, non-infected/susceptible, susceptible/resistant, resistant/non-infected, totally, four biological replicates in each line. A Dye swap was used in each pair of comparisons including AN/AS, AS/AR, AR/AN; BN/BS, BS/BR, and BR/BN. Background subtracted signal intensity were collected from 24 arrays and normalized for data analysis.

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The acute host-response of turkeys colonized with Campylobacter coli

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