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Monitoring and risk profiling of Salmonella and Escherichia coli in chicken layer farms and retail table eggs in Western Australia

Sodagari, Hamid (2021) Monitoring and risk profiling of Salmonella and Escherichia coli in chicken layer farms and retail table eggs in Western Australia. PhD thesis, Murdoch University.

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The overall goal of this research was to advance the understanding of Salmonella and E. coli in the egg industry in WA. The first objective of this study is to assess the prevalence, serotype diversity, and genomic characterization of Salmonella in the egg industry (retail and farm environment) in WA. The second objective of this study is to improve the broader understanding of antimicrobial resistance and genomic characterization of E. coli in retail eggs.

The results indicated Salmonella recovery of 11.5% (23/200) in collected retail eggs and 35% (93/265) of the environmental samples collected from layer farms. Salmonella Typhimurium and Salmonella Infantis were the most prevalent serovars in both farm and retail investigations. All Salmonella isolated from retail table eggs were susceptible to all antimicrobials tested and only two isolates were found to be resistant to ampicillin. The results of the questionnaire from egg businesses in WA highlighted the need for effective management practices and biosecurity measures cleaning and disinfection of sheds, regular Salmonella testing programs, rodent control, vaccination, and provision of uncontaminated feed.

Whole genome comparative analysis of retail isolates indicated an association between Salmonella genomic variation and the management system used to raise poultry for egg production. Our analysis indicated that Salmonella isolated from free-range retail eggs were carrying fewer virulence factors compared to isolates sourced from retail eggs branded as barn and cage eggs. Moreover, a very low carriage of resistance genes was detected in the isolates recovered from free-range produced eggs.

The highest frequencies of non-susceptibility among selected generic E. coli isolated from retail eggs were observed against tetracycline (49%) and ampicillin (36%). We also reported the first detection of non-wild-type E. coli isolates against fluoroquinolones (ciprofloxacin) in supermarket eggs in Australia.

The outcomes of these studies indicate the importance of further investigations on Salmonella and generic E. coli at the human-food of animal origin interface in WA. Findings and recommendations outlined in this thesis could be used to develop future management strategies in public health to better control of foodborne zoonotic diseases in Australia.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Veterinary Medicine
United Nations SDGs: Goal 12: Responsible Consumption and Production
Supervisor(s): Wang, Penghao, Sahibzada, Shafi, Habib, Ihab and Robertson, Ian
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