The Campylobacter jejuni Type VI Secretion System Enhances the Oxidative Stress Response and Host Colonization.

The role of the Type VI secretion system (T6SS) in Campylobacter jejuni is poorly understood despite an increasing prevalence of the T6SS in recent C. jejuni isolates in humans and chickens. The T6SS is a contractile secretion machinery capable of delivering effectors that can play a role in host colonization and niche establishment. During host colonization, C. jejuni is exposed to oxidative stress in the host gastrointestinal tract, and in other bacteria the T6SS has been linked with the oxidative stress response. In this study, comparisons of whole genome sequences of a novel human isolate 488 with previously sequenced strains revealed a single highly conserved T6SS cluster shared between strains isolated from humans and chickens. The presence of a functional T6SS in the 488 wild-type strain is indicated by expression of T6SS genes and secretion of the effector TssD. Increased expression of oxidative stress response genes katA, sodB, and ahpC, and increased oxidative stress resistance in 488 wild-type strain suggest T6SS is associated with oxidative stress response. The role of the T6SS in interactions with host cells is explored using in vitro and in vivo models, and the presence of the T6SS is shown to increase C. jejuni cytotoxicity in the Galleria mellonella infection model. In biologically relevant models, the T6SS enhances C. jejuni interactions with and invasion of chicken primary intestinal cells and enhances the ability of C. jejuni to colonize chickens. This study demonstrates that the C. jejuni T6SS provides defense against oxidative stress and enhances host colonization, and highlights the importance of the T6SS during in vivo survival of T6SS-positive C. jejuni strains.

Production and characterization of anti-Campylobacter jejuni IgY derived from egg yolks.

BACKGROUND: Campylobacter jejuni is a major cause of foodborne disease having chickens as an important reservoir. Its control at the farm would lower the contamination of the final products and therefore also lower the risk of transmission to humans. At the farm, C. jejuni is rarely found in chickens before they reach 2 weeks of age. Past studies have shown that maternal antibodies could hamper C. jejuni gut colonization. The objective of this study was to compare protocols to use in order to produce anti-C. jejuni antibodies derived from egg yolks in the perspective to be used as feed additives for the control of chicken C. jejuni colonization. Laying hens were naturally contaminated with four well-characterized strains or injected with either outer membrane proteins or formalin-killed whole bacteria derived from these same strains. Eggs were collected and IgYs present in the yolks were extracted. The amount and the specificity of the recovered antibodies were characterized. RESULTS: It was observed that injection yielded eggs with superior concentrations of both total and anti-C. jejuni antibodies. Equivalent performances for antibodies recovered from all protocols were observed for the ability of the antibodies to agglutinate the live C. jejuni homologous strains, to hinder their motility or to lyse the bacteria. Western blot analyses showed that proteins from all strains could be recognized by all IgY extracts. All these characteristics were strain specific. The characterization assays were also made for heterologous strains and weaker results were observed when compared to the homologous strains. CONCLUSIONS: Based on these results, only an IgY quantitative based selection can be made in regards to which protocol would give the best anti-C. jejuni IgY enriched egg-yolks as all tested protocols were equivalent in terms of the recovered antibody ability to recognized the tested C. jejuni strains.

Current and Potential Treatments for Reducing Campylobacter Colonization in Animal Hosts and Disease in Humans.

Campylobacter jejuni is the leading cause of bacteria-derived gastroenteritis worldwide. In the developed world, Campylobacter is usually acquired by consuming under-cooked poultry, while in the developing world it is often obtained through drinking contaminated water. Once consumed, the bacteria adhere to the intestinal epithelium or mucus layer, causing toxin-mediated inhibition of fluid reabsorption from the intestine and invasion-induced inflammation and diarrhea. Traditionally, severe or prolonged cases of campylobacteriosis have been treated with antibiotics; however, overuse of these antibiotics has led to the emergence of antibiotic-resistant strains. As the incidence of antibiotic resistance, emergence of post-infectious diseases, and economic burden associated with Campylobacter increases, it is becoming urgent that novel treatments are developed to reduce Campylobacter numbers in commercial poultry and campylobacteriosis in humans. The purpose of this review is to provide the current status of present and proposed treatments to combat Campylobacter infection in humans and colonization in animal reservoirs. These treatments include anti-Campylobacter compounds, probiotics, bacteriophage, vaccines, and anti-Campylobacter bacteriocins, all of which may be successful at reducing the incidence of campylobacteriosis in humans and/or colonization loads in poultry. In addition to reviewing treatments, we will also address several proposed targets that may be used in future development of novel anti-Campylobacter treatments.

Ex vivo proteomics of Campylobacter jejuni 81-176 reveal that FabG affects fatty acid composition to alter bacterial growth fitness in the chicken gut.

Campylobacter jejuni is one of the leading causes of foodborne gastrointestinal illness worldwide. Here we performed ex vivo proteomic analysis of C. jejuni 81-176 in chicken, a main reservoir for human infection. At 0, 1 and 4 weeks post-infection (p.i.) with the GFP-expressing 81-176 strain, inocula were recovered from chicken ceca by cell sorting using flow cytometry. iTRAQ-coupled 2D-LC-MS/MS analyses that detected 55 C. jejuni proteins, among which either 3 (FabG, HydB, CJJ81176_0876) or 7 (MscS, CetB, FlhF, PurH, PglJ, LpxC, Icd) proteins exhibited >1.4-fold-increased expression at 1 or 4 week(s) p.i. compared with those at 0 weeks p.i., respectively. Deletion of the fabG gene clearly decreased the proportion of bacterial unsaturated fatty acids (UFAs) and chicken colonization. The UFA proportion of the parental strain was not altered when grown at 42 °C. These findings suggest that FabG might play a pivotal role in UFA production, linked to bacterial adaptation in the poultry host. To our knowledge, this is the first example of ex vivo C. jejuni proteomics, in which fatty acid metabolism might affect bacterial adaptation to the chicken host.