Shiga-toxigenic Escherichia coli (STEC) are an important cause of gastroenteritis in Australia and is a notifiable pathogen. Infections may result in life threatening complications such as haemolytic uremic syndrome (HUS) in children and thrombocytopenia pupura (TTP) in adults. The epidemiology of STEC infections in Australia differs from many other countries, as non-O157 serogroups are responsible for the majority of cases and O157 doesn’t tend to cause severe disease or large outbreaks.
The Queensland Health Public Health Microbiology Laboratory is responsible for screening all symptomatic patient faeces specimens from Queensland hospital and private laboratories. In August 2013, a number of O157 cases were identified by the laboratory in quick succession, all of whom reported attending the Animal Boulevard at a large Agricultural show. A public health response was initiated including: enhanced surveillance, public health alerts, case questionnaires and contact testing. Identification of new primary and secondary cases continued until late September with a total of 57 laboratory confirmed cases, forming the largest O157 outbreak ever reported in Australia.
This outbreak required an extensive investigation through the collaborative efforts of the Queensland Public Health Units, the Communicable Diseases Unit, Biosecurity Queensland and the Public Health Microbiology laboratory. We report here on the real time analysis of the outbreak, the laboratory investigation of potential sources of the outbreak and the molecular characterisation of the outbreak strain, including the role of whole genome sequencing.