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The effect of environmental stress and rosemary extract on Campylobacter virulence and pathogenesis

Campylobacter as a foodborne pathogen developed survival mechanisms to overcome extra-intestinal environmental stresses including food processing. Despite the prevalence of human campylobacteriosis, the pathogenesis of infection is still poorly understood. We studied stress-mediated resistance to evaluate the involvement of stress response mechanisms in survival and virulence modulation of campylobacters. We determined the presence of virulence gene (cdtB, cdtC, virB11, ceuEJ, ceuEC, cadF) and assessed the physiological and morphological changes upon stresses (culturability, viability, morphology). Beside physico – chemical stress conditions, also the activity of alternative antimicrobial agent was tested according to bacterial survival and morphology changes. In our previous work we confirmed environmental stress factors may have implications in the pathogenesis of campylobacteriosis. Using in vitro cell culture models for studying adhesion, invasion and intracellular survival by Caco-2 cells or J774 murine macrophages we indicated oxygen exposure may be involved. In this study we focus in animal model on the kinetics of bacterial clearance from different organs (liver, spleen), using campylobacters exposed to selected stresses and rosemary plant extract. BALB/c mice were intravenously injected with stressed campylobacters and bacterial invasion into their livers and spleens was followed. At different time points after infection, organs were aseptically removed, dissected and the number of CFU was determined. Bacteriological and histopathological analyses of mice organs were performed. Plasma from the infected animals was tested for systemic cytokine production (IL-6, IL-10, IL-12, TNF-alpha, IFN-gamma). The results will be discussed to point on the fact that understanding of involvement and interactions of different defense mechanism (stress response, resistance) on bacterial survival and infectivity is vital for quantitative microbial risk assessment purposes and improved food safety. Non-lethal stresses induce higher resistance to subsequent stresses and can eventually change also bacterial virulence properties.

Campylobacter jejuni; environmental stress; rosemary extract; virulence; pathogenesis

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