Novel functionalization of Ti-V alloy and Ti-II using atomic layer deposition for improved surface wettability.

Surface wettability characteristics of commercially pure titanium (CP-Ti/Ti-II) and titanium Grade 5 alloy (Ti-6Al-4V/Ti-V) with 10nm-thick atomic layer deposited (ALD) TiO2 from Tetrakis DiEthyl Amino Titanium and water vapor were studied in conjunction with cleaning steps before and after the ALD treatment. The wettability characteristics of rough Ti-II and Ti-V samples were investigated after each step, that is, as received, after de-ionized (DI) water rinse followed by N2 drying, sonication in methanol, ALD treatment, and post-ALD DI water rinse. Samples without ALD or cleaning treatments were hydrophobic to variable extents, depending on exposure to different environments, surface impurities, roughness, and aging. Surface treatments reported in the literature resulted in hydrophilic/hydrophobic surfaces likely due to organic and/or inorganic impurities. In this study, (i) it is established that it is critically important to probe surface wettability after each substrate treatment; (ii) both Ti-II and Ti-V surfaces are found to become more hydrophilic after each one of the sequential treatments used; and (iii) independently of the initial wettability characteristics of Ti-II and Ti-V surfaces, the aforementioned treatments result in a water contact angle well below 10°, which is an important factor in cellular response. X-ray photoelectron spectroscopy of ALD titania films indicated trace impurities in them. Grazing incidence X-ray diffraction suggested amorphous ALD TiO2 at 200 °C; anatase TiO2 was obtained with as little as 5 min annealing at 600 °C in nitrogen.

Comparison between the biofilm initiation of Campylobacter jejuni and Campylobacter coli strains to an inert surface using BioFilm Ring Test.

AIMS: 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. METHODS AND RESULTS: 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. CONCLUSIONS: These observations suggest that the food environment and the human body could have selected strains with greater adhesion. SIGNIFICANCE AND IMPACT OF THE STUDY: 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.

Recovery methods for detection and quantification of Campylobacter depend on meat matrices and bacteriological or PCR tools.

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.

Demonstration of a protein synthesis in starved Campylobacter jejuni cells.

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.

Double staining (CTC-DAPI) for detection and enumeration of viable but non-culturable Campylobacter jejuni cells.

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.