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Type: Theses
Title: Studies on Salmonella Enterica spp isolated from egg farm environment
Author: Pande, Vivek Vinayakrao
Issue Date: 2016
School/Discipline: School of Animal and Veterinary Sciences
Abstract: Infection with Salmonella spp is among the most common causes of foodborne outbreaks of human gastrointestinal disease. Humans acquire Salmonella through the consumption of contaminated food items, including eggs and undercooked egg products. There are over 2500 Salmonella enterica serovars but globally, Salmonella Enteritidis and Salmonella Typhimurium are responsible for causing the majority of human disease. S. Enteritidis is, however, not endemic in Australia; strains of S. Typhimurium have filled this niche and are frequently isolated during cases of egg related foodborne illness. Over the last decade, cases of salmonellosis have increased, representing a significant public health issue. The experiments presented in this thesis were designed to investigate aspects of antimicrobial resistance, layer hen infection, biofilm forming ability of Salmonella spp on eggshell and the efficacy of organic acids on controlling Salmonella biofilms. Antimicrobial resistance was characterised for multiple Salmonella isolated from the layer hen environment. The majority of Salmonella isolates (91.72%; 133/145) were susceptible to all antimicrobials tested. This finding indicates that there is minimal public health risk associated with emergence of antibiotic resistant Salmonella within the Australian layer industry. An infection trial investigated the ability of S. Typhimurium to colonise reproductive organs and contaminate developing eggs. Intermittent but persistent faecal shedding of Salmonella after oral infection was observed for 15 weeks post infection. Further, S. Typhimurium caused eggshell contamination and colonised the reproductive tissue however, S. Typhimurium was not isolated from the internal egg contents. These findings indicate that horizontal transmission through contaminated faeces is the main route of egg contamination with S. Typhimurium in laying hens. Biofilm formation was dependent on both temperature and serovar. At ambient temperature, Salmonella isolates attached and formed biofilm on eggshells however, differences between strains of Salmonella serovars were evident in eggshell biofilm formation. The anti-bacterial and anti-biofilm activity of commercial organic acid products against S. enterica isolates was further investigated. The result of this experiment showed no significant differences between isolates of representative Salmonella serovars in respect of inhibitory and bactericidal dilutions of each product. Two out of three commercial organic acid products tested in this study significantly reduced viable cells from 3 and 5 day old biofilms in a dose and time dependent manner. None of the tested products completely eliminated biofilm cells under any of the tested conditions. In conclusion, the results presented here improve our understanding of the risks of egg associated S. enterica spp. Knowledge gained from these experiments could contribute to the development of improved guidelines for food safety and public health in Australia.
Advisor: Chousalkar, Kapil
McWhorter, Andrea
Dissertation Note: Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Animal and Veterinary Sciences, 2016.
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
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