We analyzed in vitro stress responses and the consequent in vivo modulation of Campylobacter pathogenicity as a result of the exposure of the C. jejuni to environmental stress (starvation, oxidative stress, heat shock). In vitro, the influence of starvation and oxidative stress has milder effect than that of heat shock, although all of the stress conditions influenced the survival of C. jejuni. Prestarvation did not contribute to improved survival of C. jejuni cells during oxygen exposure. Changes in bacteria numbers and the levels of several cytokines (IL6, IL10, IL12, TNFα in IFNγ) were followed in vivo, in liver homogenates from the mice intravenously infected with either control (untreated) or stressed C. jejuni. The most pronounced differences were in interferonγ and interleukin 10 productions, indicating their roles in the immune response to C. jejuni infection. The study of environmental impact on bacterial virulence reveals that microbial adaptation during tresschallenge is crucial not just for pathogen survival out of the host, but also during host–pathogen nteractions, and thus for the bacterial pathogenicity.
The increasing prevalence of intestinal bacteria Campylobacter and their increased antibiotic resistance is most likely due to the use of antibiotics in animal production. This is only in recent years restricted or prohibited, so natural phenolic compounds of plant origin can be further developed for potential use in controlling Campylobacter. Multiple mechanisms associated with antibiotic resistance have been identified in Campylobacter spp., while the mechanism involved in the resistance to phenolics is not known. Using mutants that lack the functional genes coding for the CmeB and CmeF efflux pump proteins and the CmeR transcriptional repressor; and EPIs, we demonstrated that complex efflux mechanisms are involved in the resistance of C. jejuni to phenolic compounds and extracts of plant phenolics. Particularly, the CmeABC efflux pump is a significant player in reducing the susceptibility to the phenolics, while CmeDEF plays a modest role in the resistance. Additionally, our results suggest that nonCmeABC and nonCmeDEF efflux systems also contribute to Campylobacter resistance to phenolic compounds. These findings represent the first comprehensive evaluation of the anti-Campylobacter activities of natural phenolics and suggest that alternative compounds can be further developed to control Campylobacter contamination in food production and processing, or as therapeutics for clinical treatment of campylobacteriosis.
The article was published among top 15 % group of food science & technology journals. We confirmed a direct link between stress response and infectivity of C. jejuni. We also established new functional model of the intestinal epithelium, which accords with the properties of normal, noncarcinogenic small intestinal epithelial cells (PSI). Heat stress increased only adhesion, while oxygen reduced their adhesion. Nutrient limitation reduced all virulence properties. There was no correlation between TER and the translocation capacity.
In the article, published in quality microbiological journal, we determined the impact of environmental stresses on bacterial cells. The comparison of different environmental stress conditions showed that starvation severely impaired Campylobacters physiology, VBNC formation and virulence. However, the lower metabolic activity of starved cells was not a dormant state, since they survived within Caco2 enterocites up to 4 days and caused systemic campylobacteriosis also in a mouse model. This indicates the connection between bacterial environmental stress response and their virulence properties.