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A laboratory-scale model is developed to study the mechanism involved in the horizontal transport of Escherichia coli under saturation-excess flow conditions, focusing on the potential for E. coli to attach to soil particles during transport. The results have shown that in runoff generated by saturation-excess conditions, bacteria are rapidly transported across the surface and have little opportunity to interact with the soil matrix.

Freshly made and aged cowpats were exposed to simulated rainfall, and samples of the cowpat material and runoff were collected. The findings indicate that cowpats could remain a significant source of Escherichia coli in overland flow for more than 30 days.

The impact of phenotypic variation on the formation of pure-species biofilms on a stainless steel surface by a virulent smooth isolate of Listeria monocytogenes and the selection of a revertant smooth morphotype in broth culture is described. Results show that a biological role for the rough colony morphotype in the colonization of abiotic surfaces, while perturbations of the SecA2 secretion pathway appear to be involved in transitions between the rough and smooth morphotypes.

The study presents the characterization of the target as well as potential mechanisms of monolaurin resistance in Enterococcus faecalis to assess its ability to act as a food preservative. The results show that a change in the cell surface hydrophobicity increases the resistance of the substance.

Survival, recoverability and sublethal injury of two strains of Listeria monocytogenes, Scott A and an environmental strain KM, on exposure to sea water at 12·8 or 20·8 °C was determined using in situ diffusion chambers. Plate counts were used to assess recoverability and injury while 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) reduction was used to determine respiratory activity. T90 values (times for 10-fold decreases in numbers of recoverable cells) on non-selective medium (trypticase soya agar with 0·6% yeast extract) at 12·8 and 20·8 °C were 61·7 and 69·2 h for L. monocytogenes Scott A, and 103·0 and 67·0 h for L. monocytogenes KM, respectively. On selective medium (Oxford agar), T90 values at 12·8 and 20·8 °C were 60·6 and 56·9 h for L. monocytogenes Scott A, and 83·0 and 65·9 h for L. monocytogenes KM, respectively. With Scott A, the percentage of sublethally injured cells at 12·8 and 20·8 °C was 1·7 and 17·7%, respectively, while for KM the values were 19·0 and 1·6%, respectively. The fraction of cells reducing CTC but which were not recoverable on plating progressively increased on exposure to sea water. Listeria monocytogenes KM challenged at 58 °C showed an apparent increase in heat resistance after exposure to sea water at 20·8 °C for 7 d (D58= 2·64 min) compared with before exposure (D58= 1·24). This increase in thermal resistance was not apparent at temperatures greater than 63 °C, and analysis of the best-fit regression lines fitted to the thermal data obtained from the two cell populations indicated that their thermal resistance was not significantly different (P > 0·05) over the temperature range tested (58–62 °C). [ABSTRACT FROM AUTHOR]

The production of Greenshell mussel (Perna canaliculus) products involves a heating process, known as a blanching or conditioning step, which facilitates opening and inhibits enzymes which can reduce the shelf-life of mussel products. To determine whether this initial heating process was also listericidal, thermal death times were determined for seven strains of Listeria monocytogenes in raw Greenshell mussels. D-values at 58, 59, 60, 61 and 62 deg.C were calculated to be 17.19, 11.32, 7.46, 4.91, and 3.24 minutes respectively, giving a z value of 5.52 deg.C. This information combined with information on the coretemperatures of mussels during processing will enable processors to implement processing regimes to ensure the elimination of any L. monocytogenes cells associated with the raw product. Such a processing regime has the additional benefit of reducing the carriage of pathogensinto the processing facility. [ABSTRACT FROM AUTHOR]

Establishing the factors which influence the attachment of bacteria to surfaces is important in both preventing and enhancing biofilm formation. The initial hour of attachment of Pseudomonas aeruginosa to ZnSe and to TiO2 from solutions of different ionic strength and pH was studied using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. The TiO2 surface was prepared by dip-coating a ZnSe internal reflection element, which produced a ∼50 nm thick, continuous flat film. At pH 6.3 attachment was found to increase with ionic strength up to 0.03 mol l−1 but to decrease at 0.15 mol l−1. At an ionic strength of 0.003 mol l−1 attachment increased with pH from 4 to 6.3 to 10, but at ionic strength of 0.03 mol l−1 attachment was greater at pH 6.3 than at pH 10. The influence of ionic strength appears to be due to charge factors and/or related changes in the degree of extension of bacterial surface polymers. The complex trends in the influence of pH on attachment can not be explained solely in terms of bacterial and substrate charge, bacterial surface polymer extension or bacterial metabolic activity. [Copyright &y& Elsevier]

Objectives: To analyse whether a specific cytokine pattern is elicited in response to the autoantigen proteinase 3 (PR3) in active Wegener's granulomatosis (WG)., Methods: Six-colour flow cytometry was used to analyse cytokine production and surface markers of the total CD4+ T-cell population ex vivo and in PR3-stimulated T-cell lines of patients with active PR3-ANCA-positive WG, PR3-ANCA-negative Churg-Strauss syndrome (CSS), and healthy controls (HC)., Results: The cytokine response of the total PB CD4+ T cell population was skewed towards distinct pro-inflammatory cytokine patterns in WG (Th1-type) and CSS (Th17, Th1-/Th2-type). Th2-type as well as Th17 cell populations including Th17/Th1, Th17/Th2 and Th22 cells were elicited in response to PR3 stimulation in WG. In contrast, CSS patients displayed a Th2-type dominated response following PR3 stimulation., Conclusions: These data suggest that the cytokine response of the total CD4+ T-cell population and PR3-specific cells is influenced by the underlying disorder.

The initiation of biofilm formation is poorly understood, and in particular, the contribution of chemical bond formation between bacterial cells and metal surfaces has received little attention. We have previously used in situ infrared spectroscopy to show, during the initial stages of Pseudomonas aeruginosa biofilm formation, the formation of coordinate covalent bonds between titanium dioxide particle films and pyoverdine, a mixed catecholate and hydroxamate siderophore. Here we show using infrared spectroscopy that pyoverdine can also form covalent bonds with particle films of Fe2O3, CrOOH, and AlOOH. Adsorption to the metal oxides through the catechol-like 2,3-diamino-6,7-dihydroxyquinoline part of pyoverdine was most evident in the infrared spectrum of the adsorbed pyoverdine molecule. Weaker infrared absorption bands that are consistent with the hydroxamic acids of pyoverdine binding covalently to TiO2, Fe2O3, and AlOOH surfaces were also observed. The adsorption of pyoverdine to TiO2 and Fe2O3 surfaces showed a pH dependence that is indicative of the dominance of the catechol-like ligand of pyoverdine. Infrared absorption bands were also evident for pyoverdine associated with the cells of P. aeruginosa on TiO2 and Fe2O3 surfaces and were notably absent for genetically modified cells unable to synthesize or bind pyoverdine at the cell surface. These studies confirm the generality of pyoverdine-metal bond formation and suggest a wider involvement of siderophores in bacterial biofilm initiation on metals.