Downregulation of Salmonella Virulence Gene Expression During Invasion of Epithelial Cells Treated with Lactococcus lactis subsp. cremoris JFR1 Requires OppA.

Invasion of Salmonella into host intestinal epithelial cells requires the expression of virulence genes. In this study, cell culture models of human intestinal cells (mucus-producing HT29-MTX cells, absorptive Caco-2 cells, and combined cocultures of the two) were used to determine the effects of Lactococcus lactis subsp. cremoris treatments (exopolysaccharide producing and nonproducing strains) on the virulence gene expression of Salmonella Typhimurium and its mutant lacking the oligopeptide permease subunit A (ΔoppA). During the course of epithelial cell (HT29-MTX, Caco-2, and combined) infection by Salmonella Typhimurium DT104, improved barrier function was reflected by increased transepithelial electrical resistance in cells treated with both strains of L. lactis subsp. cremoris. In addition, virulence gene expression was downregulated, accompanied with lower numbers of invasive bacteria into epithelial cells in the presence of L. lactis subsp. cremoris treatments. Similarly, virulence gene expression of Salmonella was also suppressed when coincubated with overnight cultures of both L. lactis subsp. cremoris strains in the absence of epithelial cells. However, in medium or in the presence of cell cultures, Salmonella lacking the OppA permease function remained virulent. HT29-MTX cells and combined cultures stimulated by Salmonella Typhimurium DT104 showed significantly lower secretion levels of pro-inflammatory cytokine IL-8 after treatment with L. lactis subsp. cremoris cell suspensions. Contrarily, these responses were not observed during infection with S. Typhimurium ΔoppA. Both the exopolysaccharide producing and nonproducing strains of L. lactis subsp. cremoris JFR1 exhibited an antivirulence effect against S. Typhimurium DT104 although no significant difference between the two strains was observed. Our results show that an intact peptide transporter is essential for the suppression of Salmonella virulence genes which leads to the protection of the barrier function in the cell culture models studied.

Effect of fermented milk from Lactococcus lactis ssp. cremoris strain JFR1 on Salmonella invasion of intestinal epithelial cells.

The process of fermentation contributes to the organoleptic properties, preservation, and nutritional benefits of food. Fermented food may interfere with pathogen infections through a variety of mechanisms, including competitive exclusion or improving intestinal barrier integrity. In this study, the effect of milk fermented with Lactococcus lactis ssp. cremoris JFR1 on Salmonella invasion of intestinal epithelial cell cultures was investigated. Epithelial cells (HT29-MTX, Caco-2, and cocultures of the 2) were treated for 1 h with Lactococcus lactis ssp. cremoris JFR1 fermented milk before infection with Salmonella enterica ssp. enterica Typhimurium. Treatment with fermented milk resulted in increased transepithelial electrical resistance, which remained constant for the duration of infection (up to 3 h), illustrating a protective effect. After gentamicin treatment to remove adhered bacterial cells, enumeration revealed a reduction in numbers of intracellular Salmonella. Quantitative reverse-transcription PCR data indicated a downregulation of Salmonella virulence genes hilA, invA, and sopD after treatment with fermented milk. Fermented milk treatment of epithelial cells also exhibited an immunomodulatory effect reducing the production of proinflammatory IL-8. In contrast, chemically acidified milk (glucono delta-lactone) failed to show the same effect on monolayer integrity, Salmonella Typhimurium invasion, and gene expression as well as immune modulation. Furthermore, an oppA knockout mutant of Salmonella Typhimurium infecting treated epithelial cells did not show suppressed virulence gene expression. Collectively, these results suggest that milk fermented with Lactococcus lactis ssp. cremoris JFR1 is effective in vitro in the reduction of Salmonella invasion into intestinal epithelial cells. A functional OppA permease in Salmonella is required to obtain the antivirulence effect of fermented milk.

Control of Salmonella Newport on cherry tomato using a cocktail of lytic bacteriophages.

Bacteriophages have been envisioned as tools to control a variety of foodborne pathogenic bacteria. Salmonella is a foodborne pathogen that is a threat to public health around the world. Contaminated tomatoes have been associated with several Salmonella outbreaks. Hence, the objective of this work was to identify and characterize different lytic bacteriophages against Salmonella Newport, as one of top ten Salmonella serovars associated with human salmonellosis in North America, and then apply these phages to enhance the safety of cherry tomatoes. Four lytic phages against Salmonella Newport were selected based on their ability to lyse a majority of the 26 screened Salmonella serovars. The selected phages belong to Myoviridae (vB_SnwM_CGG4-1, vB_SnwM_CGG4-2) and Siphoviridae (vB_SnwM_CGG3-1, vB_SnwM_CGG3-2) families. They were found to be stable at different temperatures and pH, have latent periods ranging from 53 to 65 min and burst sizes from 92 to 177. In addition, the two Myoviridae phages have a lower frequency of developing bacteriophage insensitive mutants when compared with the Siphoviridae phages. No significant change in virulence gene expression was observed in the developed bacteriophage insensitive mutants when compared to the parental phage sensitive strain. Furthermore, the vB_SnwM_CGG4-1 genome revealed no homology to virulence or lysogenic genes. A phage cocktail was used to control the growth of S. Newport in broth medium and on contaminated cherry tomato. Complete inhibition of bacterial growth in broth medium was observed at 25 °C for 24 h. In addition, a 4.5 log10 unit reduction in the bacterial count was observed when applying the phage cocktail onto contaminated tomatoes stored at 22 °C for 3 days. These findings suggest that the isolated phages can be used for biocontrol of S. Newport to improve the safety of ready-to-eat (RTE) produce.

Evaluation of protective effect of Lactobacillus acidophilus La-5 on toxicity and colonization of Clostridium difficile in human epithelial cells in vitro.

Clostridium difficile infection is a range of toxin - mediated intestinal diseases that is often acquired in hospitals and small communities in developed countries. The main virulence factors of C. difficile are two exotoxins, toxin A and toxin B, which damage epithelial cells and manifest as colonic inflammation and mild to severe diarrhea. Inhibiting C. difficile adherence, colonization, and reducing its toxin production could substantially minimize its pathogenicity and lead to faster recovery from the disease. This study investigated the efficacy of probiotic secreted bioactive molecules from Lactobacillus acidophilus La-5, in decreasing C. difficile attachment and cytotoxicity in human epithelial cells in vitro. L. acidophilus La-5 cell-free supernatant (La-5 CFS) was used to treat the hypervirulent C. difficile ribotype 027 culture with subsequent monitoring of cytotoxicity and adhesion. In addition, the effect of pretreating cell lines with La-5 CFS in protecting cells from the cytotoxicity of C. difficile culture filtrate or bacterial cell attachment was examined. La-5 CFS substantially reduced the cytotoxicity and cytopathic effect of C. difficile culture filtrate on HT-29 and Caco-2 cells. Furthermore, La-5 CFS significantly reduced attachment of the C. difficile bacterial cells on both cell lines. It was also found that pretreatment of cell lines with La-5 CFS effectively protected cell lines from cytotoxicity and adherence of C. difficile. Our study suggests that La-5 CFS could potentially be used to prevent and cure C. difficile infection and relapses.

From Bits and Pieces to Whole Phage to Nanomachines: Pathogen Detection Using Bacteriophages.

The innate specificity of bacteriophages toward their hosts makes them excellent candidates for the development of detection assays. They can be used in many ways to detect pathogens, and each has its own advantages and disadvantages. Whole bacteriophages can carry reporter genes to alter the phenotype of the target. Bacteriophages can act as staining agents or the progeny of the infection process can be detected, which further increases the sensitivity of the detection assay. Compared with whole-phage particles, use of phage components as probes offers other advantages: for example, smaller probe size to enhance binding activity, phage structures that can be engineered for better affinity, as well as specificity, binding properties, and robustness. When no natural binding with the target exists, phages can be used as vehicles to identify new protein-ligand interactions necessary for diagnostics. This review comprehensively summarizes many uses of phages as detection tools and points the way toward how phage-based technologies may be improved.

Optimizing Generic Cerambycid Pheromone Lures for Australian Biosecurity and Biodiversity Monitoring.

The cerambycid beetles comprise a diverse family that includes many economically important pests of living and dead trees. Pheromone lures have been developed for cerambycids in many parts of the world, but to date, have not been tested in Australia. In this study, we tested the efficacy of several pheromones, identified from North American and European species, as attractants for cerambycids at three sites in southeast Queensland, Australia. Over two field seasons, we trapped 863 individuals from 47 cerambycid species. In the first season, racemic 3-hydroxyhexan-2-one was the most attractive compound among the eight pheromones tested. Subsequently, we aimed to optimize trapping success by combining this compound with other components. However, neither the addition of other pheromone components nor host plant volatiles improved the efficacy of 3-hydroxyhexan-2-one alone. We also tested a generic pheromone blend developed for North American cerambycids, and found that only the combination of this blend with host plant volatiles improved trapping success. The Australian cerambycid fauna is not well known, and effective lures for use in trapping beetles would greatly assist in the study of this important group. Effective semiochemical lures would also have implications for biosecurity through improved monitoring for invasive species.

In vitro screening of mare's milk antimicrobial effect and antiproliverative activity.

The aims of this study were to examine the effect of mare's milk on virulence gene expression of Salmonella Typhimurium and observe its potential activity on proliferation of adenocarcinoma Caco-2 cells. Different supernatants of mare's milk, raw or heat-treated at 65°C for 15 s or 30 min, were studied. The changes in hilA gene expression of Salmonella Typhimurium in presence of mare's milk supernatants were assessed using a reporter luminescent strain. A significant decrease in hilA gene expression was observed with all tested supernatants. Virulence gene expression was then assessed using qPCR on a wild-type strain of Salmonella Typhimurium. A significant decrease of hilA and ssrB2 gene expression was observed with raw milk supernatants but not with heat-treated supernatants. The same supernatants were administered to Caco-2 cells to measure their proliferation rate. A significant reduction of proliferative effect was observed only with raw milk supernatants. This study reports that raw mare's milk was able to modulate virulence gene expression of Salmonella Typhimurium and exerts antiproliferative effects on Caco-2 cells. These results may offer new approaches for promoting gastrointestinal health.

Pulsed electric field processing preserves the antiproliferative activity of the milk fat globule membrane on colon carcinoma cells.

The present work evaluated the effect of processing on the antiproliferative activities of milk fat globule membrane (MFGM) extracts. The antiproliferative activity on human adenocarcinoma HT-29 cells of untreated MFGM extracts were compared with those extracted from pasteurized cream, thermally treated cream, or cream subjected to pulsed electrical field (PEF) processing. The PEF with a 37 kV/cm field strength applied for 1,705µs at 50 and 65°C was applied to untreated cream collected from a local dairy. Heating at 50 or 65°C for 3min (the passage time in the PEF chamber) was also tested to evaluate the heating effect during PEF treatments. The MFGM extracted from pasteurized cream did not show an antiproliferative activity. On the other hand, isolates from PEF-treated cream showed activity similar to that of untreated samples. It was also shown that PEF induced interactions between ß-lactoglobulin and MFGM proteins at 65°C, whereas the phospholipid composition remained unaltered. This work demonstrates the potential of PEF not only a means to produce a microbiologically safe product, but also as a process preserving the biofunctionality of the MFGM.

Antimicrobial light-activated materials: towards application for food and environmental safety.

AIMS: To produce light-activated antimicrobial materials composed of the photodynamic dye phloxine B incorporated into paper or cellulose membranes and to investigate ability of these materials to decrease bacterial loads on their surfaces as well as on food surfaces that were in contact with these materials under illumination with regular white light. METHODS AND RESULTS: Antimicrobial cellulose-based materials with incorporated phloxine B were produced using a layer-by-layer deposition method. Antimicrobial properties of the materials were tested in model systems as well as for decontamination of food and food contact surfaces. Pseudomonas aeruginosa, Listeria monocytogenes and Bacillus anthracis were efficiently killed by exposure of the bacterial suspension to the dye-containing material under illumination with white light, but Salmonella Typhimurium and Escherichia coli O157:H7 were only partially affected. Application of the materials for decontamination of food surfaces artificially contaminated with L. monocytogenes was shown to be ineffective, while the self-decontamination of the material surface by exposure to white light resulted in eradication of L. monocytogenes cells from the material surface. CONCLUSIONS: The developed materials showed significant self-decontaminating ability when under illumination; however, decontamination of food surfaces in contact with the developed materials was not achieved. SIGNIFICANCE AND IMPACT OF THE STUDY: The study demonstrates the antibacterial activity of materials with incorporated photodynamic dyes when under illumination with regular-intensity white light. Possible uses of the light-activated antimicrobial materials for food processing, as food contact surfaces, and surfaces in public areas to prevent cross-contamination are discussed.

Differential effects of lactobacilli on activation and maturation of mouse dendritic cells.

Lactic acid bacteria (LAB) are of interest because of their potential to modulate immune responses. The effects of LAB range from regulation to stimulation of the immune system. A series of studies were performed in vitro to study the effects of six lactic acid bacteria (LAB), Lactobacillus helveticus LH-2, Lactobacillus acidophilus La-5, La-115, La-116 and La-14, and Lactobacillus salivarius, on maturation and activation of mouse dendritic cells. Production of tumour necrosis factor (TNF)-?, interleukin (IL)-6 and IL-10 by dendritic cells (DCs) was determined after treating cells with live LAB. The expression of DC maturation markers, CD80 and CD40, was also measured using flow cytometry after stimulation with LAB. In addition, the expression of Toll-like receptors (TLRs) 2, 4 and 9 by DCs stimulated with LAB was measured. Our results revealed that LAB act differentially on pro-inflammatory and anti-inflammatory cytokine production and induction of co-stimulatory molecules by DCs. Specifically, L. salivarius was found to be the most effective LAB to induce pro-inflammatory cytokine production and expression of co-stimulatory molecules. Moreover, La-14, La-116 and La-5 induced moderate maturation and activation of DCs. On the other hand, LH-2 and La-115 were the least effective lactobacilli to induce DC responses. The present study also revealed that L. salivarius was able to induce the expression of TLR2, 4 and 9 by DCs. In conclusion, various strains and species of LAB can differentially regulate DC activation and maturation, providing further evidence that these bacteria may have the ability to influence and steer immune responses in vivo.

Lactobacillus acidophilus modulates the virulence of Clostridium difficile.

Clostridium difficile is a spore-forming, toxin-producing, anaerobic bacterium that colonizes the human gastrointestinal tract. This pathogen causes antibiotic-associated diarrhea and colitis in animals and humans. Antibiotic-associated diseases may be treated with probiotics, and interest is increasing in such uses of probiotics. This study investigated the effect of Lactobacillus strains on the quorum-sensing signals and toxin production of C. difficile. In addition, an in vivo experiment was designed to assess whether Lactobacillus acidophilus GP1B is able to control C. difficile-associated disease. Autoinducer-2 activity was measured for C. difficile using the Vibrio harveyi coupled bioluminescent assay. Cell extract (10µg/mL) of L. acidophilus GP1B exhibited the highest inhibitory activity among 5 to 40µg/mL cell-extract concentrations. Real-time PCR data indicated decreased transcriptional levels in luxS, tcdA, tcdB, and txeR genes in the presence of 10µg/mL of cell extract of L. acidophilus GP1B. Survival rates at 5d for mice given the pathogen alone with L. acidophilus GP1B cell extract or L. acidophilus GP1B were 10, 70, and 80%, respectively. In addition, the lactic acid-produced L. acidophilus GP1B exhibits an inhibitory effect against the growth of C. difficile. Both the L. acidophilus GP1B and GP1B cell extract have significant antipathogenic effects on C. difficile.

A fluorescence-based method coupled with Disruptor filtration for rapid detection of F + RNA phages.

UNLABELLED: F + RNA phages are commonly used as indicators of faecal contamination. This study evaluated a fluorescent method for the detection of F + RNA phages based on testing the phage-mediated release of ß-galactosidase. Factors that may potentially interfere with phage detection were investigated, and the assay was optimized. Low numbers of F + RNA phages were detected by the fluorescent method coupled with a concentration step using a Disruptor filter. The fluorescent method, when used alone, detected 1 log PFU ml(-1) of F+RNA phages within 3 h, while 0.01 PFU ml(-1) was detected within 5 h when the method was combined with the concentration step. This is the first time to combine a fluorescent method with a filtration step by the use of Disruptor filter for rapid detection of low numbers of F + RNA phages, and this method can be adapted to detect other lytic phages infecting host cells that produce measurable enzyme activity. SIGNIFICANCE AND IMPACT OF THE STUDY: A fluorescent method coupled with Disruptor filtration was evaluated for the first time to rapidly detect low numbers of F + RNA phages. Rapid detection of F + RNA phages provides an effective way to monitor faecal contamination of environmental water and thus helps prevent contamination of fresh produce via irrigation.

Cell-free preparations of Lactobacillus acidophilus strain La-5 and Bifidobacterium longum strain NCC2705 affect virulence gene expression in Campylobacter jejuni.

Campylobacter spp. are among the most commonly reported bacterial causes of acute diarrheal disease in humans worldwide. Potential virulence factors include motility, chemotaxis, colonization ability, adhesion to intestinal cells, invasion and epithelial translocation, intracellular survival, and formation of toxins. Probiotic Lactobacillus and Bifidobacterium strains are known to have an inhibitory effect against the growth of various foodborne pathogens. The objective of this study was to investigate the effect of Lactobacillus acidophilus strain La-5 and Bifidobacterium longum strain NCC2705 cell-free spent media (CFSM) on the expression of virulence genes (cadF, cdtB, flaA, and ciaB) of Campylobacter jejuni strain 81-176 and a luxS mutant, using real-time PCR. Our results demonstrated that the CFSM of both probiotic strains were able to down-regulate the expression of ciaB (ratio of -2.80 and -5.51, respectively) and flaA (ratio of -7.00 and -5.13, respectively) in the wild-type Campylobacter strain. In the luxS mutant, where the activated methyl cycle is disrupted, only the ciaB gene (ratio -7.21) was repressed in the presence of La-5 CFSM. A supplementation of homocysteine to restore the disrupted cycle was able to partially reestablish the probiotic effect of both strains. luxS and the activated methyl cycle might play an active role in the modulation of virulence of C. jejuni by probiotic extracts.

Lactobacillus helveticus: the proteolytic system.

Lactobacillus helveticus is one of the species of lactic acid bacteria (LAB) most commonly used in the production of fermented milk beverages and some types of hard cheese. The versatile nature of this bacterium is based on its highly efficient proteolytic system consisting of cell-envelope proteinases (CEPs), transport system and intracellular peptidases. Besides use of L. helveticus in cheese processing, the production of fermented milk preparations with health promoting properties has become an important industrial application. Studies have shown that fermented dairy products are able to decrease blood pressure, stimulate the immune system, promote calcium absorption, and exert an anti-virulent effect against pathogens. These beneficial effects are produced by a variety of peptides released during the hydrolysis of milk proteins by the proteolytic system of L. helveticus, which provides the bacterium with its nutritional requirements for growth. In recent years, studies have focused on understanding the factors that affect the kinetics of milk protein hydrolysis by specific strains and have concentrated on the effect of pH, temperature, growth phase, and matrix composition on the bacterial enzymatic system. This review focuses on the role of the proteolytic system of L. helveticus in the production of bioactive compounds formed during fermentation of dairy products. Taking advantage of the powerful proteolytic system of this bacterium opens up future opportunities to search for novel food-derived compounds with potential health promoting properties.

Bovine milk fat globule membrane affects virulence expression in Escherichia coli O157:H7.

The aim of this study was to examine the effect of the bovine milk fat globule membrane (MFGM) on the virulence of Escherichia coli O157:H7. The MFGM was extracted from raw or heat-treated milk, resulting in 2 preparations differing in protein composition. Both heated and raw MFGM exerted an inhibitory effect on Shiga toxin gene expression by E. coli O157:H7 (ratios of -7.69 and -5.96, respectively). Interestingly, the effect was stronger with heated MFGM, with a larger decrease in expression of the virulence gene fliC (ratio of -9.43). The difference in effect observed between heated and raw MFGM could be explained by the difference in protein composition between the 2 preparations. These results show, for the first time, a specific effect of MFGM on expressionof Shiga toxin genes as well as genes involved in the motility of E. coli O157:H7. This may offer a new approach to mitigate the adverse health effects caused by E. coli O157:H7 infections.

Glucose decreases virulence gene expression of Escherichia coli O157:H7.

Escherichia coli O157:H7 is responsible for a human toxico-infection that can lead to severe complications such as hemolytic uremic syndrome. Inside the intestine, E. coli O157:H7 forms typical attaching-effacing lesions and produces Shiga toxins. The genes that are responsible for these lesions are located in a pathogenicity island called the locus of enterocyte effacement (LEE). LEE gene expression is influenced by quorum sensing through the luxS system. In this study, the effect of glucose on the expression of several genes from LEE, on the expression of Shiga toxin genes, and on the expression of luxS was assessed with real-time, reverse transcription PCR. All concentrations of glucose (from 0.1 to 1%) were able to down-regulate genes from the LEE operon. A slight down-regulation of genes implicated in Shiga toxin expression was also observed but was significant for low doses of glucose (0.1 to 0.5%) only. A slight but significant increase in luxS expression was observed with 1% glucose. This confirms that in addition to quorum sensing, the presence or absence of nutrients such as glucose has an impact on the down- or upregulation of LEE-encoded virulence genes by the bacterium. The influence of glucose on the virulence of E. coli O157:H7 has received little attention, and these results suggest that glucose can have an important effect on the virulence of E. coli O157:H7.

The influence of size and shape of microorganism on pulsed electric field inactivation.

In this paper the effect of microorganism size and shape on the killing efficiency of pulsed electric field (PEF) is investigated both experimentally and using a transient finite element program. The effect of cell size, membrane thickness, cell shape (spherical, elliptical, and cylindrical) on the calculated transmembrane voltage is studied. It has been found that both the cell size and cell membrane thickness have significant effect on the induced field across the cell membrane. The findings of the simulation results have been evaluated by comparing the trends with some experimental results. Five different types of microorganisms that have different shapes and dimensions have been inoculated with water at a conductivity level of 100 µS/cm and have been treated with the application of a pulsed electric field of 70 kV/cm. Significant difference in bacteria reduction was noticed between the treated cells which could be attributed to the cell size and shape.

Biocontrol of Listeria monocytogenes and Escherichia coli O157:H7 in meat by using phages immobilized on modified cellulose membranes.

The ability of phages to specifically interact with and lyse their host bacteria makes them ideal antibacterial agents. The range of applications of bacteriophage can be extended by their immobilization on inert surfaces. A novel method for the oriented immobilization of bacteriophage has been developed. The method was based on charge differences between the bacteriophage head, which exhibits an overall net negative charge, and the tail fibers, which possess an overall net positive charge. Hence, the head would be more likely to attach to positively charged surfaces, leaving the tails free to capture and lyse bacteria. Cellulose membranes modified so that they had a positive surface charge were used as the support for phage immobilization. It was established that the number of infective phages immobilized on the positively charged cellulose membranes was significantly higher than that on unmodified membranes. Cocktails of phages active against Listeria or Escherichia coli immobilized on these membranes were shown to effectively control the growth of L. monocytogenes and E. coli O157:H7 in ready-to-eat and raw meat, respectively, under different storage temperatures and packaging conditions. The phage storage stability was investigated to further extend their industrial applications. It was shown that lyophilization can be used as a phage-drying method to maintain their infectivity on the newly developed bioactive materials. In conclusion, utilizing the charge difference between phage heads and tails provided a simple technique for oriented immobilization applicable to a wide range of phages and allowed the retention of infectivity.

Bioluminescent high-throughput assay for the bacteria adherence to the tissue culture cells.

The goal of this study was develop a rapid high-throughput method for the assessment of the bacterial adhesion to tissue culture cells and test this method by investigation of the adhesion and growth of pathogenic and non-pathogenic Escherichia coli strains in the presence of HeLa human epithelial cells. Fifteen strains of E. coli were transformed with a plasmid carrying the entire lux operon of Photorhabdus luminescens to make them bioluminescent. By using the Time-to-Detection approach and bioluminescence imaging in microplate format, the adherence and growth of bacteria in tissue culture medium in the presence of HeLa cells was monitored. It was observed that Eagle's minimal essential medium (EMEM) supplemented with 10% fetal bovine serum (FBS) significantly inhibited growth of E. coli. However, in the presence of HeLa cells the detected growth of E. coli was similar to the growth observed in LB medium. It was established that the initial number of E. coli cells present in the microplate directly correlated with the time necessary for the bioluminescence signal to reach the threshold level, hence allowing the accurate assessment of the adhered cells within 8-10 h. Neither bacterial adherence nor growth kinetics correlated with the pathogenicity of the strain though they were strain-specific. The developed approach provided new information on the interaction of E. coli with epithelial cells and could be used for both pathogenicity research and for the screening of potential therapeutic agents for the ability to minimize pathogen colonization of human tissues.

Expression and characterization of cell-signalling molecules in Campylobacter jejuni.

AIMS: This study investigated the production and effects of cell-signalling compounds on selected survival and virulence mechanisms of Campylobacter jejuni. METHODS AND RESULTS: The production of Autoinducer 1 (AI-1) compounds by Camp. jejuni was investigated in-vitro using a variety of available AI-1 bioassays. We further examined the role of a range of commercially available homoserine lactones (HSL) and a novel compound (cjA) isolated from Camp. jejuni. The selected attributes included the transformation to a viable but nonculturable (VBNC) state, biofilm formation, interleukin 8 (IL-8) stimulation in INT-407 cells and virulence gene expression as determined by qRT-PCR. This study is the first to report an HSL or HSL mimic produced by Camp. jejuni. Short chained HSLs and the novel compound cjA prolonged the delay to a VBNC state as well as inhibiting biofilm formation and the majority of HSLs examined and the HSL mimic cjA significantly affected virulence gene expression as well as increasing the production of IL-8 in challenged INT-407 cells. CONCLUSIONS: Despite the lack of a homologous HSL kinase or sensor, Camp. jejuni appears to produce, as well as detect, exogenous signalling molecules and respond accordingly to aid in the survival and virulence capabilities of this micro-organism. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that Camp. jejuni is able to detect and utilize as well as possibly produce cell-signalling molecules that enhance both survival and virulence attributes. This possibility opens a new field in the search for Camp. jejuni reduction and elimination strategies.