Outbreak of Salmonella infantis gastroenteritis among people who had eaten at a hash house in southern Italy

Abstract

Objectives: To describe an outbreak of acute gastroenteritis in people who had eaten at a hash house in southern Italy.

Study design: Case-control study.

Methods: A clinical case of gastroenteritis was defined as a person who had eaten at the hash house from 29 August to 4 September 2011 and who experienced defined gastrointestinal symptoms within 72 hours, or a person with a laboratory-confirmed salmonella infection without symptoms. A convenience sample was enrolled as the control group. Environmental and human samples were collected, and Salmonella infantis was identified by polymerase chain reaction. Univariate analysis was performed for each food type, and multivariate analysis was performed for each food type and demographic variable (gender, age).

Results: Twenty-three cases of gastroenteritis were notified between 1 and 4 September 2011, two of which were admitted to the local hospital. Multivariate analysis showed that porchetta [odds ratio (OR) 22.0, 95% confidence interval (CI) 3.2-152.6, z = 3.13, P = 0.002] and roasted meat (OR 14.4, 95% CI 1.7-122.0, z = 2.45, P = 0.014) were associated with gastrointestinal symptoms. Environmental and human isolates exhibited the same sequence type (ST 32).

Conclusions: This experience highlighted that, in the control of a foodborne outbreak, integrated epidemiological and laboratory surveillance enables rapid identification of the source of infection, thus reducing the risk of an epidemic.

Keywords: Case–control study; Food safety; Molecular characterization; Outbreak; Salmonella infantis.