[Show abstract][Hide abstract] ABSTRACT: The influence of redox alteration on the growth and proteomic pattern of Listeria monocytogenes was investigated. A redox shock was induced in cultures by addition of 3 mM ferricyanide (FeCN) and 6 mM dithiothreitol (DTT) to increase or to decrease respectively the redox potential naturally occurring at the beginning of growth. In both conditions, the reducing and oxidizing redox shock had a strong influence, decreasing the maximum growth rate by half compared to a control culture. The proteomic analysis of L. monocytogenes performed by two-dimensional difference gel electrophoresis (2D-DIGE) exhibited twenty-three proteins differentially expressed (p < 0.05), amongst these, many were oxidoreductases, and proteins involved in cellular metabolism (glycolysis, protein synthesis), detoxification (kat) or adhesion (Lmo1634).
Journal of proteomics 11/2012; 79. DOI:10.1016/j.jprot.2012.11.010 · 3.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Food-borne human infection with Campylobacter jejuni is a medical concern in both industrialized and developing countries. Efficient eradication of C. jejuni reservoirs within live animals and processed foods is limited by the development of antimicrobial resistances and by practical problems related to the use of conventional antibiotics in food processes. We have investigated the bacteriostatic and bactericidal activities of two phytochemicals, allyl-isothiocyanate (AITC), and benzyl isothiocyanate (BITC), against 24 C. jejuni isolates from chicken feces, human infections, and contaminated foods, as well as two reference strains NCTC11168 and 81-176. AITC and BITC displayed a potent antibacterial activity against C. jejuni. BITC showed a higher overall antibacterial effect (MIC of 1.25-5 μg mL(-1)) compared to AITC (MIC of 50-200 μg mL(-1)). Both compounds are bactericidal rather than bacteriostatic. The sensitivity levels of C. jejuni isolates against isothiocyanates were neither correlated with the presence of a GGT (γ-Glutamyl Transpeptidase) encoding gene in the genome, with antibiotic resistance nor with the origin of the biological sample. However the ggt mutant of C. jejuni 81-176 displayed a decreased survival rate compared to wild-type when exposed to ITC. This work determined the MIC of two ITC against a panel of C. jejuni isolates, showed that both compounds are bactericidal rather than bacteriostatic, and highlighted the role of GGT enzyme in the survival rate of C. jejuni exposed to ITC.
Frontiers in Cellular and Infection Microbiology 04/2012; 2:53. DOI:10.3389/fcimb.2012.00053 · 3.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Campylobacter, a leading cause of food-borne illness worldwide, has a widespread distribution with a broad range of animal hosts and environmental reservoirs. The genetic description of bacterial strains is a powerful tool for epidemiological studies but can be impaired by the high genomic variability of Campylobacter. Our study aimed (i) at investigating the genotypic instability of Campylobacter generated either in vitro by subculturing or after in vivo passage on specific pathogen-free pigs and (ii) at evaluating the suitability of typing methods to detect such variation. Pigs were inoculated per os with three Campylobacter strains (one C. coli originating from pig faeces, one C. jejuni and one C. coli originating from poultry faeces) alone or in mixture and non-inoculated pigs were housed in adjacent pens. Genotypic instability was investigated using both macrorestriction combined with pulsed-field gel electrophoresis analysis (PFGE) and PCR restriction fragment length polymorphism analysis of the flaA gene (flaA PCR-RFLP). No variability in the genetic profile was observed for the three strains maintained through twenty times subculturing events in vitro. Genotypic variability was evidenced in vivo only in pigs inoculated with C. coli of porcine origin, either alone or in a mix, with both genotyping methods. In our study, for one porcine C. coli strain, 13% and 21% of variability were generated in the digestive tract of pigs by PFGE and flaA PCR-RFLP typing methods, respectively. This study is a first approach for a better understanding of the genomic instability of Campylobacter in pig under field conditions.
[Show abstract][Hide abstract] ABSTRACT: Bacteriocins produced by Lactobacillus salivarius have been recently recognized as a natural means to control Campylobacter and Salmonella in live poultry. This finding is of relevance since Campylobacter jejuni and Campylobacter coli are the predominant species isolated from poultry that are associated with human campylobacteriosis. In the present work, lactic acid bacteria (LAB) isolated from the cecum of twenty Tunisian chickens were identified and those isolates with antagonism against Campylobacter were further characterized. Following their preliminary confirmation as LAB, 150 strains were identified by combining morphological criteria, biochemical tests, and molecular methods, the latter inluding intergenic 16S- 23S PCR, specific lactobacilli PCR, and a biphasic approach. Most of the LAB isolated belonged to the genus Lactobacillus, among them Lb. sakei (33.3%), Lb. salivarius (19.4%), Lb. reuteri (8.6%), and Lb. curvatus (8.6%). The other LAB strains included those of the genus Weissella (16.7%), Enterococcus faecalis (5.3%), Leuconostoc mesenteroides (2.7%), Lactococcus graviae (2.7%), and Streptococcus sp. (2.7%). The Lactobacilli strains were tested for their antagonism against C. jejuni and C. coli. The activity of three of them, Lb. salivarius SMXD51, Lb. salivarius MMS122, and Lb. salivarius MMS151, against the aforementioned target strains could be ascribed to the production of bacteriocins.
International Microbiology 06/2011; 14(2):103-10. DOI:10.2436/20.1501.01.140 · 1.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A polyphasic taxonomic study, using phenotypic, phylogenetic and genotypic characterization, was performed on five Gram-stain-positive, catalase-negative, coccus-shaped Vagococcus-like bacteria isolated from the spoilage microbiota of cooked shrimp. Comparative 16S rRNA gene sequence analysis indicated that the isolates belonged to the genus Vagococcus. The five isolates shared 100% 16S rRNA gene sequence similarity, and representative strain CD276(T) formed a branch that was distinct from the type strains of the six recognized species of the genus Vagococcus (Vagococcus fluvialis CCUG 32704(T), V. salmoninarum NCFB 2777(T), V. lutrae CCUG 39187(T), V. fessus M2661/98/1(T), V. carniphilus ATCC BAA-340(T) and V. elongatus PPC9(T)). The taxonomic position of strain CD276(T) was clarified using DNA-DNA hybridization, pulsed-field gel electrophoresis of whole-genome DNA, G+C content determination, cell-wall peptidoglycan typing, fatty acid analysis and biochemical characterization. On the basis of this evidence, a novel species, Vagococcus penaei sp. nov., is proposed. The type strain is CD276(T) (=LMG 24833(T) =CIP 109914(T)).
International Journal of Systematic and Evolutionary Microbiology 11/2009; 60(Pt 9):2159-64. DOI:10.1099/ijs.0.012872-0 · 2.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The adhesion to an inert surface (the first step of biofilm formation) of the two main pathogenic Campylobacter species, Campylobacter jejuni and Campylobacter coli, isolated from diverse origins, was compared.
Adhesion assays were conducted in 96-well, polystyrene microtiter plates using the BioFilm Ring Test method. This new technique, based on magnetic bead entrapment, was shown to be suitable for analysing the adhesion of Campylobacter sp. strains by comparing the adhesion of four C. jejuni strains as revealed by the BioFilm Ring Test and immunodetection. Among the 46 strains tested, C. jejuni and C. coli displayed different adhesion capabilities ranging from no adhesion to strong adhesion. However, no strain of C. coli was strongly adherent, and statistically, C. coli adhered less to an inert surface than C. jejuni. In addition, strains isolated from animals or carcasses were less adherent than those isolated from food-processing and clinical cases.
These observations suggest that the food environment and the human body could have selected strains with greater adhesion.
The adhesion capability of strains could partly explain the cross-contamination or re-contamination of food products by Campylobacter. This property could provide a mode of survival for Campylobacter in the food chain.
[Show abstract][Hide abstract] ABSTRACT: Campylobacter is one of the main causes of human foodborne bacterial disease associated with meat consumption in developed countries. Therefore, the most effective approach for recovery and detection of Campylobacter from meat should be determined. Two hundred ninety pork skin and chine samples were inoculated with Campylobacter jejuni NCTC 11168 and two strains of Campylobacter coli. Campylobacter cells were then recovered from suspensions and enumerated by direct plating. Campylobacter recovery was evaluated by comparing results for two methods of sample collection (swabbing and mechanical pummeling) and three recovery fluids (peptone water, 5% glucose serum, and demineralized water). End-point multiplex PCR was performed to evaluate the compatibility of the recovery fluids with direct PCR detection techniques. Mean recovery ratios differed significantly between pork skin and chine samples. Ratios were higher for mechanical pummeling (0.53 for pork skin and 0.49 for chine) than for swabbing (0.31 and 0.13, respectively). For pork skin, ratios obtained with peptone water (0.50) and with glucose serum (0.55) were higher than those obtained with demineralized water (0.16). Significant differences were not observed for chine samples. Direct multiplex PCR detection of Campylobacter was possible with pork skin samples. The tools for Campylobacter recovery must be appropriate for the meat matrix to be evaluated. In this study, less than 66% of inoculated Campylobacter was recovered from meat. This underestimation must be taken into account for quantitative risk analysis of Campylobacter infection.
Journal of food protection 10/2006; 69(9):2100-6. · 1.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: For many years, environmental microbiologists working on water samples, have reported differences between bacterial counts performed by culture and by microscopy. These observations have led to the demonstration of the viable but non-culturable (VNC) state in bacteria. Some hygienist specialists underlined the risk presented by pathogenic bacteria in the VNC state. The VNC state in bacteria has been studied by a number of authors, but the relation between VNC state and bacterial stress response has not been established yet, while the VNC state is generally described in responses to adverse conditions. Campylobacter jejuni enter the VNC state in response to starvation. In our study, we searched for a protein synthesis in the first hours of the cell starvation exposure. Three Campylobacter jejuni strains were suspended in filtered, sterilized, distilled water, and incubated at 4 degrees C with gentle shaking (100 rpm). After 1, 2, 3, 4 and 5 h of starvation, C. jejuni cells were removed and subjected to a heat shock (55 degrees C, 3 min) and to a conductimetric assay. Results obtained showed that a protein synthesis occurred in the onset of the starvation period, and that these improved the nutrient assimilation and enhanced the heat resistance in starved cells.
International Journal of Food Microbiology 05/2000; 55(1-3):63-7. DOI:10.1016/S0168-1605(00)00195-1 · 3.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Direct microscopic enumeration of viable Campylobacter jejuni cells (ie, respiring bacteria) were performed in both culturable and non-culturable states. Five different C jejuni strains were used, including a reference strain, ATCC 33291. Cells from all five strains were incubated alone with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), a redox dye. It was reduced by an electron transport chain to an insoluble red fluorescent CTC formazan salt, which accumulated intracellularly. The presence of these red CTC crystals in the bacteria cells was indicative of cellular respiratory activity. Counterstaining with 4'-6 diamino-2 phenylindole (DAPI), which fluoresces in blue, made a suitable contrast and allowed simultaneous enumeration of total and viable bacteria on a single filter. Four hours of incubation with 5 mM CTC under a microaerobic atmosphere was found to be the optimal condition yielding the maximum number of respiring cells (both culturable and non-culturable). When used in combination with standard culture techniques, double staining makes it possible to monitor the viable but non-culturable cells of jejuni obtained by starvation more easily than with the direct viable count procedure.
Veterinary Research 01/1997; 28(6):547-55. · 2.82 Impact Factor