An outbreak of Salmonella Infantis gastroenteritis in a residential aged care facility associated with thickened fluids

Abstract

Twenty-two confirmed cases of Salmonella Infantis were identified in 70 residents of high-level care areas of a residential aged care facility in Sydney in April 2010 during an outbreak of gastroenteritis. A retrospective cohort study was conducted to identify a possible cause. Consuming a soft diet, puréed diet, or thickened fluid were each independently associated with illness. A logistic regression showed consumption of thickened fluid to be the only significant exposure associated with illness (adjusted odds ratio 11·8, 95% confidence interval 1·9-75·9). It was postulated that the thickened fluid had been contaminated by chicken mince, a sample of which also cultured S. Infantis. This finding reinforces the need to educate food-handlers on the risk of potential cross-contamination; it also highlights the need to consider all dietary components, such as thickened fluids, as potential vehicles for transmission in an outbreak.

Fig. 1.

Cases of S. Infantis by date of symptom onset and ward.

Fig. 2.

Pulsed-field gel electrophoresis of clinical samples and selected food-source samples of S. Infantis. M, Marker lanes; lane 1, epidemiologically unrelated isolate; lane 2, chicken meat isolate (surveillance isolate); lane 3, chicken feed isolate (surveillance isolate); lane 4, chicken mince isolate (from aged care facility); lane 5, patient isolate; lane 6, staff isolate; lane 7, epidemiologically unrelated isolate.