Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/128364
Type: Thesis
Title: A study of non-typhoidal Salmonella virulence
Author: Moyle, Talia Sheryli
Issue Date: 2020
School/Discipline: School of Animal and Veterinary Sciences
Abstract: Salmonella is a major cause of foodborne gastroenteritis world-wide. Salmonella serovars are broadly classified as typhoidal or nontyphoidal. Nontyphoidal Salmonella serovars include Salmonella Typhimurium (S. Typhimurium) and Salmonella Enteritidis (S. Enteritidis). In Australia, S. Typhimurium is the most commonly identified serovar during human outbreaks relating to eggs and egg products. Recently, during egg related outbreaks, Salmonella Hessarek (S. Hessarek) has increasingly been identified in South Australia. The aims of this thesis were to determine whether S. Typhimurium and S. Hessarek have an enhanced ability to penetrate the egg shell, to determine the effects of storage temperature on growth of S. Typhimurium and S. Hessarek within the egg, to examine the effect of storage temperature of eggs infected with S. Typhimurium when infected eggs were consumed and finally to study the effects of storage time and storage temperature on aioli infected with S. Typhimurium when infected aioli was consumed. Egg shells were infected with S. Typhimurium and S. Hessarek by dipping them in a bacterial suspension either immediately after lay or after being cooled to room (shed) temperature, then stored at either 5°C or 25°C. Egg contents were also infected with S. Typhimurium and S. Hessarek and stored at either 5°C or 25°C to examine bacterial growth in the egg contents. When eggs were infected immediately after lay, before the eggs cooled to room temperature, S. Typhimurium and S. Hessarek were able to penetrate into the shell pores, but not into the contents. Egg contents that were infected and stored at 5℃ were negative for bacterial growth after direct plating, whereas eggs stored at 25℃ were positive for bacterial growth after direct plating. Infected eggs were then stored at either 5°C or 25°C prior to being fed to mice to examine the effect of storage temperature of S. Typhimurium infected eggs when consumed. No mice fed infected egg components stored at 5°C exhibited signs of Salmonellosis. Mice fed infected yolk stored at 25℃ quickly developed disease symptoms. It took longer for the animals fed infected egg albumen and shell wash stored at 25℃ to begin showing symptoms of disease. Aioli, a raw egg product, was then infected and stored at either 5°C or 25°C for different periods of time (12, 24, 36, 48 or 72 hours). It was then fed to mice, to examine the effect of storage temperature and storage time on S. Typhimurium infected aioli when consumed. No infection occurred in mice fed infected aioli stored at 25℃, whereas two mice from the infected aioli stored for 24 hours 5°C and one mouse from the infected aioli stored for 12 hours at 5°C did succumb to salmonellosis. The bacteria enumerated from the organs of these mice was comparable to the number of bacteria enumerated from the control mice fed infected aioli, that were culled. Results of these experiments indicated the effect of storage temperature on bacterial growth within the egg and growth/survival in eggs and egg products prior to infection and the subsequent occurrence of salmonellosis.
Advisor: Chousalkar, Kapil
McWhorter, Andrea
Dissertation Note: Thesis (MPhil) -- University of Adelaide, School of Animal and Veterinary Sciences, 2020
Keywords: Salmonella
Salmonella Typhimurium
Salmonella Hessarek
egg
aioli
storage temperature
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: http://www.adelaide.edu.au/legals
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