Differences in host breed and diet influence colonization by Campylobacter jejuni and induction of local immune responses in chicken

Abstract

Background: Chickens are regarded as the main reservoir for human campylobacteriosis. Little is known about the interaction between Campylobacter jejuni (C. jejuni) and chickens. This interaction may be influenced by the stage of maturation of the immune system, developing gut microbiota composition and other factors including breed and diet. Our aim was to investigate the impact of breed, and diet on C. jejuni colonization and host immune responses in chickens. Birds were inoculated with 10⁴ colony forming units (CFU) of C. jejuni or diluent at one (Exp. 1) or 22 (Exp. 2) days post hatch. We compared local immune cell subpopulations, cytokine expression levels, and gut microbiota composition between broiler-type (BT) and layer-type (LT) birds fed with either commercial broiler feed (bf) or layer feed (lf).

Results: Lower colonization rates were observed in the older age group independent of breed and diet. Independent of breed, birds fed with bf showed higher CFU of C. jejuni compared to lf-fed groups. Campylobacter jejuni-inoculation had a significant effect on lymphocyte numbers and cytokine expression levels in BT birds independent of feeding strategy (p < 0.05). These effects were not detected in LT birds, only LT birds fed with bf showed a significant increase in IL-8-expression at 7 days post C. jejuni inoculation compared to LT-control birds (p < 0.05). Diet influenced gut microbiota composition in a comparable manner between BT and LT birds, but changes in microbiota composition associated with C. jejuni inoculation varied between breeds.

Conclusions: Diet and breed influenced C. jejuni colonization, immune responses and microbiota composition to a different extent comparing between LT and BT birds. The mechanisms behind these differences have to be elucidated further. Our results suggest that selection for more resistant breeds in combination with adapted feeding strategies may help to reduce Campylobacter colonization levels in commercial poultry in the future.

Keywords: Breed; Campylobacter jejuni; Diet; Gut microbiota; Immune response.

Fig. 1

Immunohistochemical detection of T and B lymphocytes in caecum of 1-day-old birds. Immunohistochemical detection of CD4+ (a, b), CD8β+ (c, d) and Bu1+ (e, f) lymphocytes in caecal lamina propria of birds, which had been inoculated with either C. jejuni or C. jejuni-free medium at 1 day post hatch (Experiment 1). Broiler-type (BT) (a, c, e) and layer-type (LT) (b, d, f) birds, which were fed with either broiler feed (bf) or layer feed (lf). Asterisk letters indicate significant differences between C. jejuni-inoculated (C. jejuni) and C. jejuni-free control (con) groups at the indicated days post C. jejuni inoculation (n = 6/group, p < 0.05)

Fig. 2

Immunohistochemical detection of T and B lymphocytes in caecum of 22-days-old birds. Immunohistochemical detection of CD4+ (a, b), CD8β+ (c, d) and Bu1+ (e, f) lymphocytes in caecal lamina propria of birds, which had been inoculated with either C. jejuni or C. jejuni-free medium at 22 day post hatch (Experiment 2). Broiler-type (BT) (a, c, e) and layer-type (LT) (b, d, f) birds, which were fed with either broiler feed (bf) or layer feed (lf). Asterisk letters indicate significant differences between C. jejuni-inoculated (C. jejuni) and C. jejuni-free control (con) groups at the indicated days post C. jejuni inoculation (n = 6/group, p < 0.05)

Fig. 3

Flow cytometric analysis of T lymphocytes. Flow cytometric analysis of the percentage of CD4+ intraepithelial lymphocytes (IEL) in caecum of broiler-type (BT) (a, c) and layer-type (LT) birds (b, d) fed with either broiler feed (bf) or layer feed (lf). Birds had been C. jejuni-inoculated at 1 (Exp. 1) (a, b) and 22 (Exp. 2) (c, d) days post hatch. CD4+ T cells were gated within the CD3+ IEL population. Asterisk letters indicate significant differences between C. jejuni-inoculated (C. jejuni) and C. jejuni-free control (con) groups at the indicated days post C. jejuni inoculation (n = 6/group, p < 0.05)

Fig. 4

mRNA expression levels in caecum of 1-day-old birds. IL-6 (a, b) and IL-8 (c–f) mRNA expression levels in caecum samples of broiler-type (BT; a, c, e) and layer-type (LT; b, d, f) birds fed with either broiler feed (bf) or layer feed (lf). Birds had been C. jejuni-inoculated at 1 day post hatch. Comparison of cytokine mRNA expression between C. jejuni-free control and C. jejuni-inoculated birds at 1 dpi (a–d). Comparison of cytokine mRNA expression between C. jejuni-free control and C. jejuni-inoculated birds at 7 dpi (e, f). Data are presented as the mean mRNA expression (40-Ct) normalized to 28S. Asterisk letters indicate significant differences between C. jejuni-inoculated (C. jejuni) and C. jejuni-free control (con) groups at the indicated days post C. jejuni inoculation (n = 6/group, p < 0.05)

Fig. 5

Microbiota diversity. Microbiota diversity in caecum of broiler-type (BT) and layer-type (LT) birds fed with either broiler feed (bf) or layer feed (lf). UniFrac analysis followed by PCoA indicates variability in the caecal microbiota composition based on different feeding strategy (a, b) and genetic background (c, d). “con” = C. jejuni-free control, “C. jejuni” = C. jejuni-inoculated. (Figures were generated from raw data but when we produced the figures from normalized data, these were essentially the same. We therefore used maximal data available for each sample in this figure)

Fig. 6

Gut microbiota composition. The composition of the main families present caecal microbiota in chicken. The sum of the appropriate families as indicated in the figure legend provides information on the microbiota distribution at the phylum level. Taxonomy summary and microbial diversity of the operational taxonomic units (OTU) from caecal samples collected at 7 days post inoculation from broiler-type (BT) and layer-type (LT) birds fed with either broiler feed (bf) or layer feed (lf), which had been C. jejuni-inoculated at 1 day post hatch (n = 6 per group). “con” = C. jejuni-free control, “C. jejuni” = C. jejuni-inoculation. (Figures were generated from raw data but when we produced the figures from normalized data, these were essentially the same. We therefore used maximal data available for each sample in this figure)