The epidemiology of non-typhoidal Salmonella enterica in Australia and the impact of whole genome sequencing on public health surveillance and outbreak investigation

Abstract

Salmonella is a key cause of foodborne gastroenteritis in Australia and case numbers are increasing. We used negative binomial regression to analyze national surveillance data for 2000–2013, for Salmonella Typhimurium and non-Typhimurium Salmonella serovars. We estimated incidence rate ratios adjusted for sex and age to show trends over time. Almost all states and territories had significantly increasing trends of reported infection for S. Typhimurium, with states and territories reporting annual increases as high as 12% (95% confidence interval 10–14%) for S. Typhimurium in the Australian Capital Territory and 6% (95% CI 5–7%) for non-Typhimurium Salmonella in Victoria. S. Typhimurium notification rates were higher than non-Typhimurium Salmonella rates in most age groups in the south eastern states of Australia, while non-Typhimurium rates were higher in most age groups elsewhere. The S. Typhimurium notification rate peaked at 12–23 months of age and the nonTyphimurium Salmonella notification rate peaked at 0–11 months of age. The age-specific pattern of S. Typhimurium cases suggests a foodborne origin, while the age and geographic pattern for non-Typhimurium may indicate that other transmission routes play a key role for these serovars. Introduction Salmonella enterica is transmitted via food, the environment, water, people and animals, and often causes gastroenteritis in humans [1, 2]. Worldwide, Salmonella infections, excluding those caused by S. Typhi and S. Paratyphi, were estimated in a paper published in 2010 to cause 93.8 million (90% credible interval 61.8–131.6 million) cases of gastroenteritis per year, 80.3 million of which are considered foodborne [3]. Approximately 72% of salmonellosis in Australia is estimated to be transmitted through contaminated food [1]. Common foods associated with salmonellosis in outbreak investigations and source attribution studies include eggs, poultrymeat, pork, beef, dairy products, nuts, and fresh produce [4, 5, 6, 7]. PLOS ONE | DOI:10.1371/journal.pone.0163989 October 12, 2016 1 / 11 a11111