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GENETIC STRUCTURE OF CLOSTRIDIUM DIFFICILE RECOVERED FROM ENVIRONMENTAL OR CLINICAL SOURCES AND GROWTH POTENTIAL IN FOODS

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Title: GENETIC STRUCTURE OF CLOSTRIDIUM DIFFICILE RECOVERED FROM ENVIRONMENTAL OR CLINICAL SOURCES AND GROWTH POTENTIAL IN FOODS
Author: Alammi, Sundes
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Marc, Habash
Abstract: Clostridium difficile ribotype 078 is the predominant ribotype recovered from animals and the environment, while 027 is recovered from hospital patients. The aims of this study were to i) determine the genetic relatedness among a population of C. difficile isolates (n=200) from humans, healthy animals, and the environment in Southern Ontario; ii) compare the effects of growth media, temperature, salt concentration, pH, and germinants on the growth, spore germination, and sporulation of the dominant ribotypes identified from Southern Ontario samples; and iii) determine the effect of probiotic bacteria, Lactobacillus helveticus R0052 and Pediococcus acidilactici R1001, on growth of C. difficile ribotypes 078 and 027. The dominant known ribotypes isolated from the Southern Ontario samples were 078 (79%) followed by 027 (3.5%). Pulsed field gel electrophoresis showed that some ribotype 078 isolates from animal and environmental sources were the same genotype as isolates from patients with C. difficile infections. Growth of ribotype 078 and 027 isolates was inhibited at 4 °C, below pH 6 and above pH 8 and by 8% KCl. Isolates of both ribotypes grew well on meat juice medium (MJM) and fish juice medium (FJM). Both ribotypes grew significantly better in MJM compared with brain heart infusion broth at 37 °C. Of vi importance, several agents including MJM and FJM enhanced spore germination of ribotype 078 and 027 isolates without addition of bile salt and both ribotypes could germinate in food related environments. MJM was a highly effective germinant for ribotype 078, but failed to stimulate germination of 027 isolates. The growth of C. difficile ribotype 078 and 027 isolates was inhibited by Lactobacillus helveticus R0052 and Pediococcus acidilactici R1001 in co-culture and by cell-free culture supernatants; importantly the inhibition was not attributed solely to acidity and appears to be due to factors secreted by the probiotics. Overall, the data presented several novel aspects of C. difficile ribotypes 078 and 027 including genetic relationships among isolates, interactions with factors relevant to food and to probiotic bacteria. Further for ribotype 078, the data suggest that animals, and by extension meats, could be sources of human community-acquired C. difficile infection.
URI: http://hdl.handle.net/10214/11615
Date: 2017-09-26


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