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Subject: search.filters.subject.Yersinia enterocolitica

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    Assessment of the sensitivity of current standard procedures for the isolation of Yersinia enterocolitica from pork mince : a dissertation presented in partial fulfilment (25%) of the requirements for the degree of Master of Veterinary Studies in Veterinary Public Health at Massey University
    (Massey University, 1999) Subramaniam, Durai
    Y. enterocolitica and related species have been isolated from many types of food. The majority of isolates differ in biochemical and serological characteristics from typical pathogenic strains and are termed non-pathogenic or environmental strains. Usually the number of Y. enterocolitica organisms present in food products is low compared with the dominant background flora. The ability of current enrichment procedures to recover pathogenic strains of Y. enterocolitica from different foods is often inadequate probably because different strains require different conditions for optimum growth (De Boer 1992). An efficient enrichment procedure should confer some selective advantage to the desired type of microorganism by promoting its growth relative to the competing microflora. At present, there is no single ideal isolation procedure available for the recovery of pathogenic strains of Y. enterocolitica from foods. The aim of this study was to determine the recovery rate of Y. enterocolitica biotype 4/serotype 0:3 from samples of pork mince inoculated with known numbers of the microorganism using different enrichment parameters (Time, temperature and pH) and Cefsulodin-Irgasan-Novobiocin (CIN) agar as the selective medium. The experiment was conducted in two trials using different bacterial dilutions. Three pork mince samples in duplicate were inoculated with known quantities of Y. enterocolitica biotype 4/serotype 0:3 organisms and subjected to cold enrichment in phosphate buffered saline (PBS) with a pH of 7.6, 6.6 and 5.5 at 25°C for 2 days, 10°C for 7 days and 4°C for 21 days. CIN agar was used as the selective medium. Pre-inoculation control samples were selected and plated in CIN on day O and on day 21 after PBS enrichment at 4°C. In Trial one Y. enterocolitica organisms were recovered from all 3 samples incubated at 25°C for 2 days and from 1 out of 3 inoculated samples incubated at 4°C for 21 days. There were no organisms recovered from other inoculated samples. The control sample did not show any environmental contamination with Yersinia species. In Trial two, Y. enterocolitica was recovered from 1 out of 3 duplicate samples enriched in PBS with pH 6.6 and incubated at 25°C for two days. Y. enterocolitica was not recovered from other inoculated samples. Y. intermedia was isolated from all pH, temperature and time combinations and also from control samples. The following conclusions can be drawn from this experiment. Incubation at high temperature (25°C) and short duration (48 hours) can be used as an efficient method for isolating Y. enterocolitica from pork samples. The standard incubation period of 21 days required for cold enrichment at 4°C is too long for the isolation of pathogenic strains, because of possible growth of environmental microorganisms. A pH of 6.6 is less efficient than 7.6 for enrichment although occasional isolation can be made using this pH. Enrichment in PBS with a pH of 5.5 with any time as well as temperature combinations and incubation at 10°C for 7 days are not ideal for isolation of pathogenic Yersinia enterocolitica strains. Of the three enrichments (PBS 7.6, 6.6, 5.5) used in this experiment, PBS with pH 7.6 was found to be most efficient to others.
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    Factors contributing to biofilm formation of Yersinia enterocolitica : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology, Massey University, Palmerston North, New Zealand
    (Massey University, 2016) Wang, Haoran
    Biofilms of pathogenic bacteria are recognised as a threat to food safety. The aim of the present study was to investigate the potential of Yersinia enterocolitica to form biofilms in the pork processing environment and identify the resistance of these biofilms to sanitation. The biofilm formation by Y. enterocolitica was monitored at conditions simulating pork processing environment under daily cleaning routine using an impedance method established in this study. Results showed that Y. enterocolitica had the potential to form biofilm and become resistant to sanitation in a pork processing environment. An investigation into the factors influencing biofilm formation of Y. enterocolitica indicated that the Ca2+ ion increased the level of biofilm formation. In addition, the presence of the virulence plasmid pYV is essential for the biofilm Ca2+ response. Further analysis of the bacterial cell surface properties and extracellular polymeric substance (EPS) composition suggested that the pYV+ cell surfaces are more negatively charged and more hydrophobic than the pYV- cells although no significant difference was observed with the addition of Ca2+. The pYV+ cells appear to produce more exopolysaccharide than the pYV- cells regardless of Ca2+ concentration. Ca2+ was able to increase the yield of extracellular DNA while the presence of pYV appeared to be dispensable in terms of extracellular DNA release. Analysis of cell wall protein revealed one protein expressed in the pYV+ cells but absent in the pYV- cells.
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    Effects of Yersinia enterocolitica infection on the development of the small intestine in newborn piglets : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physiology at Massey University
    (Massey University, 1993) Shu, Dairu; Shu, Dairu
    A model of bacterial gastroenteritis has been developed in which the effects of Yersinia enterocolitica infection on the structural and biochemical development of the small intestine have been examined in neonatal piglets both during the infection period (3 and 5 days postinfection) and during the subsequent recovery period after antibiotic therapy (at 14 days). The potential of oral bovine lactoferrin and another bovine milk protein for preventing or reducing the effects of Y. enterocolitica gastroenteritis have been evaluated in these piglets. Newborn, colostrum-deprived piglets were inoculated orogastrically with a high dose (about 3 x 1010 colony forming units/ml) of Y. enterocolitica serotype 0:3, biotype 4. Diarrhoea began between 40 hours and 4 days after inoculation in 18 of the 19 animals and microabscesses, the typical lesions of Yersiniosis, were present in the mucosa of the small intestine in all infected piglets. At 5 days postinfection, microabscesses also were present in the liver of 7 of 8 piglets, and in the mucosa of the stomach in 2 animals. The mucosal damage and resulting malabsorption were reflected in the lower plasma glucose, Na+ and Cl- concentrations. Yersinia enterocolitica infection reduced the body weight but not body length, but did not significantly affect the gastrointestinal tract length or weight or the growth of non-intestinal organs except the liver. There were markedly lower lactase and sucrase, but not maltase and Na+-K+-ATPase, activities in the small intestine. The mucosal protein and DNA contents and the ratio of RNA to DNA in the small intestine were not significantly different in infected animals. Rapid proliferation of crypt cells resulted in crypt enlargement in the entire small intestine, but reduced vacuolation of the epithelium of the distal small intestine. Following institution of effective antibiotic therapy, gastrointestinal lesions were absent. Compared with controls, the piglets gained body weight at the same rate, although remaining lighter in weight, and organ weights and concentrations of plasma Na+ and Cl-, but not glucose, were no different. Previously-infected piglets retained an altered profile of disaccharidase activity with a lower lactase activity, higher maltase and sucrase activities and early appearance of sucrase activity in the ileum. There were fewer vacuoles in the epithelium of the distal ileum. A bovine milk fraction, but not bovine lactoferrin, appeared to reduce the severity of the infection due to Y. enterocolitica, there being shorter crypts, fewer proliferating crypt cells and higher lactase activity. The group means for the lesion number were also much lower although not significantly different. Oral supplementation with bovine lactoferrin in the milk formula did not have any beneficial effects in the infected piglets. In non-infected piglets, lactoferrin appeared to have trophic effects on the kidney and the small intestinal crypts, increased the lactase activity and caused an unexplained reduction in plasma glucose concentration and liver weight. Yersinia enterocolitica enteritis in newborn, colostrum-deprived piglets accelerated the maturation of the epithelium of the small intestine, indicated by reduced enterocyte vacuolation and an altered disaccharidase profile.