In VivoModulation ofCampylobacter jejuniVirulence in Response to Environmental Stress

Abstract

Campylobacters have developed a number of mechanisms for responding to environmental conditions, although the different virulence properties of these cells following exposure to stress are still poorly understood. We analyzed in vitro stress responses and the consequent in vivo modulation of Campylobacter jejuni pathogenicity in BALB/c mice, 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 was milder than that of heat shock, although the majority of the stress conditions influenced the survival of C. jejuni. During starvation, C. jejuni viability was maintained longer than its culturability. Additionally, starvation elicited transformation of stressed bacteria to coccoid forms. In contrast, bacteria exposed to oxygen remained culturable, but their viability decreased. Pre-starvation did not contribute to improved survival of C. jejuni cells during oxygen exposure. Changes in bacteria numbers and the levels of several cytokines (interleukins 6 and 10, tumor necrosis factor-α, interferon-γ) were followed in vivo, in liver homogenates from the mice intravenously infected with either control (untreated) or stressed C. jejuni. The systemic infection with the control or stressed C. jejuni occurred with different production dynamics of the cytokines investigated. Starvation was the most powerful stress factor, which significantly decreased infectious potential of C. jejuni during the first 3 days postinfection. The most pronounced differences in cytokine production were found in interferon-γ and interleukin-10 production, which indicates that these have roles in the immune response to C. jejuni infection. These in vivo studies of environmental impact on bacterial virulence reveal that microbial adaptation during stress challenge is crucial not just for pathogen survival out of the host, but also during host-pathogen interactions, and thus for the bacterial pathogenicity.

Virulence genes and cytokine profile in systemic murineCampylobacter coliinfection

“…This falling pattern of bacterial numbers isolated from the liver has also been seen previously in the liver of mice infected with C. jejuni. 44 In contrast, the CFU of C. coli isolated from the spleen of the infected mice in the present study was increasing toward the last day post-infection (day 8). This might be explained by the potentially lower number of macrophages in the liver.…”

“…44 Briefly, immediately before analysis, the livers were thawed on ice and homogenized in ice-cold phosphate-buffered saline (5 mL per 1 g tissue, wet weight) using a hand-held tissue homogenizer. Following homogenization, the liver samples were centrifuged (14,000 £ g, 10 min, 4 C) to precipitate the cell debris as a pellet.…”

“…The levels of IL-6, IL-10, IL-12, TNF-a and IFN-g were determined in duplicate, using mouse cytokine enzyme-linked immunosorbent assay kits (Thermo Scientific, EM2IL6, EM2IL10, EMIL12TOT2, EMTNFA5, ESS0020), and the data are expressed in pg/mL plasma or tissue homogenate, as described previously. 44 The sensitivity levels were: IL-6, 7 pg/mL; IL-10, 12 pg/mL; TNF-a, 9 pg/mL; and IFN-g, 10 pg/mL. Control mice of the same age and sex were injected with sterile saline.…”

Anti-adhesion activity of thyme (Thymus vulgarisL.) extract, thyme post-distillation waste, and olive (Olea europeaL.) leaf extract againstCampylobacter jejunion polystyrene and intestine epithelial cells

“…A suspension of C. jejuni in brain–heart infusion broth served as the growth control. The growth curves and kinetics of inhibition were evaluated using the macrodilution method, and the antimicrobial effectiveness was determined as the percentage of growth inhibition after 24 h, calculated as in Eqn : …”

“…Foodborne illnesses continue to present a public health challenge, and societal expectations increasingly call for less risk and even greater safety than the current systems provide. An alarming increase has been seen in the prevalence of antibiotic‐resistant bacterial strains, such as Campylobacter , which are highly sensitive to environmental stress but have evolved mechanisms for survival both inside and outside the host . Campylobacter jejuni is the most common bacterial gastrointestinal pathogen in the European Union .…”