An outbreak of gastroenteritis due to Salmonella Typhimurium phage type 170 associated with consumption of a dessert containing raw egg

Eggs are frequently implicated as a source of foodborne salmonellosis. In February 2009 an investigation was commenced following reports of gastrointestinal illness among diners at a Canberra restaurant. The investigation sought to confirm the existence of an outbreak, identify a source and implement public health measures to prevent more cases. Menus and booking lists were obtained from the restaurant and a case-control study was commenced. A suspected case was defined as a person who ate at the restaurant on 13 or 14 February 2009 and subsequently developed diarrhoea and/or vomiting. Twenty cases and 31 controls were enrolled in the study. Eating a tiramisu dessert containing raw egg had a highly statistically significant association with illness (crude odds ratio 130.50, 95% confidence interval 13.54-1605.28). Among the 20 cases, nine of 12 stool samples were positive for Salmonella Typhimurium phage type 170 (STm 170). No microbiological evidence of STm 170 was obtained from the restaurant or during the egg trace-back investigation. This report highlights the risk associated with consumption of foods containing raw or undercooked shell egg

Seven Salmonella Typhimurium Outbreaks in Australia Linked by Trace-Back and Whole Genome Sequencing

Salmonella Typhimurium is a common cause of foodborne illness in Australia. We report on seven outbreaks of Salmonella Typhimurium multilocus variable-number tandem-repeat analysis (MLVA) 03-26-13-08-523 (European convention 2-24-12-7-0212) in three Australian states and territories investigated between November 2015 and March 2016. We identified a common egg grading facility in five of the outbreaks. While no Salmonella Typhimurium was detected at the grading facility and eggs could not be traced back to a particular farm, whole genome sequencing (WGS) of isolates from cases from all seven outbreaks indicated a common source. WGS was able to provide higher discriminatory power than MLVA and will likely link more Salmonella Typhimurium cases between states and territories in the future. National harmonization of Salmonella surveillance is important for effective implementation of WGS for Salmonella outbreak investigations.The authors would like to thank ACT Health, NSW Health, Queensland Health, and OzFoodNet. We would also like to thank the laboratories that performed the serotyping, MLVA, and WGS, including the ICPMR, the MDU PHL, and Queensland Health Forensic and Scientific Services. Doherty Applied Microbial Genomics is funded by the Department of Microbiology and Immunology at The University of Melbourne. The National Health and Medical Research Council, Australia, funded a Practitioner Fellowship GNT1105905 to B.P.H. and Project Grant GNT1129770 to B.P.H., D.A.W., and M.D.K. Finally, we would like to thank Milica Stefanovic and Sam McEwen for their contribution to this project. This research is supported by an Australian Government Research Training Program (RTP) Scholarshi