Outbreak of Salmonella Typhimurium phage type 135a gastroenteritis linked to eggs served at an Australian Capital Territory café

Abstract

Salmonella is an important foodborne pathogen, with eggs and egg-containing foods being frequently implicated in causing outbreaks of disease. In April 2012, an investigation was commenced after a number of cases of salmonellosis were linked to a Canberra café. The investigation sought to identify the cause of illness and to introduce public health measures to prevent further disease. A case control study was undertaken using the café's booking list to identify potential cases and controls. A structured questionnaire was developed using the café's menu, with information collected via telephone interview or email. A case was defined as any person who ate at the implicated café on 25 April 2012 and subsequently developed gastroenteritis. A total of 20 cases and 22 controls were recruited into the study. All 20 cases had faecal cultures positive for Salmonella Typhimurium phage type 135a (STm 135a). Eating eggs Benedict (odds ratio 63.00, 95% confidence interval 6.08-2771.66 P > 0.001) was significantly associated with illness. While no microbiological evidence of STm 135a was obtained from foods sampled from the café, STm 135a was recovered from swabs taken from the kitchen environment. This report illustrates an ongoing trend in Australia, where raw and minimally cooked egg-containing foods are identified as the responsible vehicles in a high proportion of foodborne Salmonella outbreaks.