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C Pin

Publications and source records attributed to C Pin.

At least 19 recordsLinked to original sources
PubMed2006

A role for the tet(O) plasmid in maintaining Campylobacter plasticity.

Genomic sequencing projects are beginning to reveal regions of extensive DNA homology between bacterial genera. Public fears of the spread of genetically modified organisms into the food chain and the increasing prevalence of multi-drug resistant disease in humans highlight the implications of horizontal gene transfer. The striking DNA sequence similarity between the two uniquely identified tetracycline resistant (Tc(R)) Campylobacter plasmids, pCC31 and pTet, suggests their conserved acquisition and maintenance within Campylobacter [Batchelor, R.A., Pearson, B.M., Friis, L.M., Guerry, P., Wells, J.M. 2004. Nucleotide sequences and comparison of two large conjugative plasmids from different Campylobacter species. Microbiology 150, 3507-3517]. It is thus likely that these and other conjugative plasmids are highly prevalent and broadly distributed across several continents. Microarray technology is now enabling fast and extensive genomic comparisons to be made and allows us to investigate intra- and inter-genetic conservation and variability. This study details the development of a microarray specific for genes from Campylobacter plasmids pCC31, pTet and pVir and its application to the analysis of Campylobacter plasmid gene presence and preservation throughout environmental and clinical isolates. Application of the iterative algorithm GENCOM (freely available at ) is used as a rapid and effective way of comparing the content and conservation of plasmids in bacteria and provides details of the Campylobacter flexible gene pool and its contribution to genomic plasticity.

Algorithms↗
PubMed2006

Indirect measurement of the lag time distribution of single cells of Listeria innocua in food.

The distribution of log counts at a given time during the exponential growth phase of Listeria innocua measured in food samples inoculated with one cell each was applied to estimate the distribution of the single-cell lag times. Three replicate experiments in broth showed that the distribution of the log counts is a linear mapping of the distribution of the detection times measured by optical density. The detection time distribution reflects the lag time distribution but is shifted in time. The log count distribution was applied to estimate the distributions of the lag times in a liquid dairy product and in liver paté after different heat treatments. Two batches of ca. 100 samples of the dairy product were inoculated and heated at 55 degrees C for 45 min or at 62 degrees C for 2 min, and an unheated batch was incubated at 4 degrees C. The final concentration of surviving bacteria was ca. 1 cell per sample. The unheated cells showed the shortest lag times with the smallest variance. The mean and the variance of the lag times of the surviving cells at 62 degrees C were greater than those of the cells treated at 55 degrees C. Three batches of paté samples were heated at 55 degrees C for 25 min, 62 degrees C for 81 s, or 65 degrees C for 20 s. A control batch was inoculated but not heated. All paté samples were incubated at 15 degrees C. The distribution of the lag times of the cells heated at 55 degrees C was not significantly different from that of the unheated cells. However, at the higher temperatures, 62 degrees C and 65 degrees C, the lag duration was longer and its variance greater.

Animals↗
PubMed2005

In vitro cell culture methods for investigating Campylobacter invasion mechanisms.

Studying the mechanisms of Campylobacter pathogenesis is complicated by the lack of simple animal models that mimic the disease seen in humans. In vitro cell culture methods provide a useful alternative to investigate the interactions between Campylobacter and the host epithelium that occur during infection. In the genomics era there is an increasing use of in vitro cell culture techniques to interrogate the potential role of different genes in pathogenesis. The aim of this review was to discuss the suitability and limitations of the various experimental approaches that might be adopted. We review current knowledge concerning the influence of cell-specific as well as bacterial factors required for Campylobacter invasion such as flagella and secreted proteins. The involvement and effects of phase variation on the results of invasion studies in cell culture emphasise the need to verify observed strain variations. We present the use of a mathematical Invasion Success Model to analyse Campylobacter invasion and show that it can be used to derive three strain dependent characteristics Imax, k, and I0. Even by combining data from independent experiments the Invasion Success Model can be used to statistically compare Campylobacter strains for their invasion of epithelial cells. Recommendations are given for the adoption of standard assay parameters and analytical methods such as the Invasion Success Model in order to facilitate comparison of data generated in different laboratories.

Animals↗
PubMed2003

Comparative genome analysis of Campylobacter jejuni using whole genome DNA microarrays.

Whole genome DNA microarrays were constructed and used to investigate genomic diversity in 18 Campylobacter jejuni strains from diverse sources. New algorithms were developed that dynamically determine the boundary between the conserved and variable genes. Seven hypervariable plasticity regions (PR) were identified in the genome (PR1 to PR7) containing 136 genes (50%) of the variable gene pool. When comparisons were made with the sequenced strain NCTC11168, the number of absent or divergent genes ranged from 2.6% (40 genes) to 10.2% (163) and in total 16.3% (269) of the genes were variable. PR1 contains genes important in the utilisation of alternative electron acceptors for respiration and may confer a selective advantage to strains in restricted oxygen environments. PR2, 3 and 7 contain many outer membrane and periplasmic proteins and hypothetical proteins of unknown function that might be linked to phenotypic variation and adaptation to different ecological niches. PR4, 5 and 6 contain genes involved in the production and modification of antigenic surface structures.

Algorithms↗
PubMed2001

A parallel study on bacterial growth and inactivation.

Pure stochastic birth process models are used to establish the connection between the traditional food microbiology concept of bacterial lag period, before the exponential growth, and the distribution of the lag times of individual cells. In a parallel way, similar study is carried out on the connection between the "shoulder" period, before the exponential decay, and the distribution of the survival times of individual cells. Formulae are derived to calculate the parameters of the growth/survival curves from the distributions of the respective parameters of individual cells. It is shown that, in some aspects, analogy, in some aspects fundamental difference exists between growth and survival modelling.

Bacteria↗
PubMed2001

An extraction chromatography method for Hf separation prior to isotopic analysis using multiple collection ICP-mass spectrometry.

A novel method for the single-step separation of Zr + Hf from all matrix elements of geological samples has been developed for Hf isotopic measurements using multiple collector-ICP-mass spectrometry. The method combines an effective sample decomposition by LiBO2 fusion with a selective separation of Hf + Zr by a solid-phase extraction material based on dipentyl pentyl phosphonate, commercially available as U-TEVA.Spec. Using this simple and rapid procedure, Hf and Zr can be isolated in a single separation step with good recoveries (>90%) and satisfactory blank levels (approximately 55 pg of Hf), so that a subsequent isotopic measurement with ICPMS is possible. An excellent separation from rock-forming constituents is achieved, including those elements (Al, P, Ti, Cr, Fe, Mo, etc.) known to interfere in conventional separation methods based on ion-exchange techniques. The potential of this new method for Hf isotopic analysis is demonstrated by replicate MC-ICPMS measurements of 176Hf/177Hf ratios in seven international reference materials of silicate rocks, spanning a range of Hf contents and bulk compositions.

Journal Article↗
PubMed2000

Predictive model for the growth of Yersinia enterocolitica under modified atmospheres.

A quadratic response surface model is presented to describe the maximum specific growth rate of Yersinia enterocolitica, at refrigeration temperatures, under modified atmospheres. The presence of CO2 affected mainly the lag phase of the organism. The length of the lag phase increased with higher levels of CO2 in the atmosphere, and this effect was more noticeable at low temperatures. The effect of oxygen was similar but less pronounced. The observed growth was slower with higher CO2. Oxygen also decreased the growth rate, but its effect was significant only when its proportion in the atmosphere was greater than about 40%. Model predictions were compared with growth rates obtained in sea food inoculated with Y. enterocolitica and packaged under modified atmospheres. Predictions were also checked to determine whether they were inside the strict interpolation region of the model.

Animals↗
PubMed1999

Validating and comparing predictive models.

The bias and accuracy factors introduced by Ross [Ross, T., 1996. Indices for performance evaluation of predictive models in food microbiology. J. Appl Bacteriol. 81, 501-508] for the evaluation of the performance of models in 'predictive food microbiology' are refined by basing the calculation of those measures on the mean square differences between predictions and observations. The use of the indices is extended by presenting formulae and methods which enable evaluation of the difference between alternative models for growth of an organism of interest over a domain of environmental factors. This is done by calculating the integral mean of the square differences between the models under investigation over the domain of the environmental variables common to those models, or a sub-region of it. The use of the techniques is exemplified by evaluating the difference between four published models for the growth rate of psychrotrophic pseudomonads.

Bias↗
PubMed1999

Validating predictive models of food spoilage organisms.

The accuracy and bias of a predictive model for the maximum specific growth rate of Pseudomonas spp. were studied by means of percentage discrepancy and bias indicators. These were calculated for observations obtained both in laboratory media and in food. When independent pseudomonad data generated in broth were compared with model predictions, the error was smaller than in the case of food. The extent to which the food structure and composition of the microflora contribute to the overall error of the model was quantified.

Animals↗
PubMed1999

Estimating bacterial growth parameters by means of detection times.

We developed a new numerical method to estimate bacterial growth parameters by means of detection times generated by different initial counts. The observed detection times are subjected to a transformation involving the (unknown) maximum specific growth rate and the (known) ratios between the different inoculum sizes and the constant detectable level of counts. We present an analysis of variance (ANOVA) protocol based on a theoretical result according to which, if the specific rate used for the transformation is correct, the transformed values are scattered around the same mean irrespective of the original inoculum sizes. That mean, termed the physiological state of the inoculum, âlpha, and the maximum specific growth rate, mu, can be estimated by minimizing the variance ratio of the ANOVA procedure. The lag time of the population can be calculated as lambda = -ln âlpha/mu; i.e. the lag is inversely proportional to the maximum specific growth rate and depends on the initial physiological state of the population. The more accurately the cell number at the detection level is known, the better the estimate for the variance of the lag times of the individual cells.

Analysis of Variance↗
PubMed1998

Predictive models as means to quantify the interactions of spoilage organisms.

The purpose of this paper is to quantify the interactions of some groups of spoilage organisms that can be usually found in refrigerated meat stored in air, such as: Enterobacteriaceae, Pseudomonas, Acinetobacter, Psychrobacter, Shewanella, Carnobacterium, Lactobacillus, Leuconostoc, Brochothrix and Kurthia spp. The growth of these organisms was studied in the range of temperature 2-11 degrees C and pH 5.2-6.4, which is characteristic of refrigerated meat. The main growth parameters (maximum specific growth rate and lag time) were modelled by multivariate quadratic polynomials of temperature and pH. The interactions of the organisms were analyzed by comparing their growth models obtained in isolation with those obtained in mixture. The difference between the models was quantified by statistical F-values which were used to measure how much the growth of an organism or group of organisms was affected by others and which of them dominated their joint growth.

Bacteria↗
PubMed1997

Virulence factors-pathogenicity relationships for Aeromonas species from clinical and food isolates.

The presence of virulence factors in 96 Aeromonas strains isolated from food and clinical samples was studied. Neither cytotoxic activity and hydrophobicity, not the presence of pili or an extra surface layer made it possible to establish differences between food and clinical strains. Statistical studies showed that cytotoxin production was associated with a positive Voges-Proskauer reaction, inability to ferment arabinose and a positive lysine decarboxylation. Therefore, when comparing cytotoxic clinical and food strains with lysine decarboxylation phenotype, there was a significant difference (p < 0.05) between the two groups. The association of a cytotoxin production and lysine decarboxylation character should thus be considered as a possible virulence marker.

Aeromonas↗
PubMed1997

Lactic acid bacteria: hydrophobicity and strength of attachment to meat surfaces.

The hydrophobicity and strength of attachment of several lactic acid bacteria with antimicrobial activity were studied. Hydrophobicity was determined by bacterial adherence to hydrocarbons (BATH; octane or xylene), adhesion to nitrocellulose filters (NCF), salt aggregation test (SAT) and adherence to phenyl-Sepharose beads (PSB). The relative hydrophobicity of lactic acid bacteria depended markedly on the method used. No correlation between either SAT or BATH (octane) and strength of attachment (Sr value) existed. However, a significant relationship between strength of attachment and BATH (xylene), NCF and PSB, respectively, was observed, showing the highest correlation coefficient (r = 0.778) for BATH (xylene).

Ammonium Sulfate↗
PubMed1996

Attachment of lactic acid bacteria to beef-muscle surfaces.

The effect of immersion time and cell concentration in the attachment of several lactic acid bacteria with antibacterial activity to beef-muscle surface was studied. The number of firmly attached bacteria increased with immersion time in the case of Pediococcus acidilacti, Lactobacillus sake, Lactococcus cremoris (two strains) and Pediococcus acidilacti. Pediococcus pentosaceus, Lactococcus lactis and Lactobacillus curvatus reached maximum adhesion after 15-30 min. The highest strength of attachment (Sr values) were observed after 15-30 min of contact time except for P. pentosaceus. For all strains, the number of bacteria adhering to meat increased with increasing cell concentration in the adhesion medium. The highest strength of attachment was observed at a cell concentration of 10(5)/mL mainly for L. sake, L. lactis and L. cremoris. Due to their attachment characteristics, L. sake, L. lactis and L. cremoris are proposed as potential biocontrol agents because they could grow on meat surface and limit the potential attachment of pathogenic microorganisms.

Animals↗
PubMed1995

Differences in production of several extracellular virulence factors in clinical and food Aeromonas spp. strains.

Production of several extracellular virulence factors (lipase, protease and haemolysin) was compared in 15 Aeromonas spp. isolated from faeces of patients with Aeromonas-associated gastroenteritis and 81 strains isolated from food. Strains from food did not show differences in production of these factors when compared with strains isolated from faeces. However, if strains were considered in relation to autoagglutination (AA) character, the AA+ differed from AA- strains in lipase and protease production. Supernatant fluids of AA+ food and human strains showed 2.5-fold more protease production than that observed in AA- strains. These two characteristics of certain Aeromonas strains could be related with the more virulent capacity.

Aeromonas↗
PubMed1994

Virulence factors in clinical and food isolates of Aeromonas species.

Virulence factors were compared in 15 Aeromonas spp. isolated from faeces of patients with Aeromonas-associated gastroenteritis and in 81 strains isolated from food. Strains from food did not show differences in the distribution of virulence factors when compared with strains isolated from faeces. However, 88.8% of Aeromonas strains isolated from food were capable of producing possible virulence factors. Characterization of 28 autoagglutinating (AA+) Aeromonas spp. indicated that the human strains differed from the food strains in hemagglutinating and hemolytic capacities. These results suggest that autoagglutination associated with hemagglutinating and hemolytic capacities in food strains may be a helpful indicator of potential pathogenicity.

Acriflavine↗
PubMed1994

Incidence of motile Aeromonas spp. in foods.

A total of 80 food samples were purchased from local retail consumer shops and examined for the presence of motile Aeromonas spp. Of the food categories tested, poultry had the highest incidence, with 100% positive. This was followed by lamb samples, with 60% positive. Raw milk and cheese samples had very low incidence (20%). No motile Aeromonas spp. were found in pre-prepared salads. Shellfish, fish, pork and beef samples had incidences of 40%. Most of the strains isolated were Aeromonas hydrophila, and for most of the food categories, no Aeromonas caviae isolates were obtained.

Aeromonas↗