Foodborne transmission of Listeria monocytogenes via ready-to-eat salad: A nationwide outbreak in Switzerland, 2013–2014. (November 2015)

• Record Type: Journal Article
• Authors: Stephan, Roger; Althaus, Denise; Kiefer, Sabine; Lehner, Angelika; Hatz, Christoph; Schmutz, Claudia; Jost, Marianne; Gerber, Nadine; Baumgartner, Andreas; Hächler, Herbert; Mäusezahl-Feuz, Mirjam
• Is Part Of: Food control. Volume 57(2015:Nov.)
• Page Start: 14
• Page End: 17
• Publication Date: 2015-11
• Subjects: Listeria monocytogenes outbreak -- Serotype 4b -- ST 4 -- Ready-to-eat salad; Food -- Quality -- Periodicals; Food -- Analysis -- Periodicals; Food handling -- Periodicals; Food industry and trade -- Quality control -- Periodicals; Aliments -- Industrie et commerce -- Qualité -- Contrôle -- Périodiques; Aliments -- Qualité -- Périodiques; Aliments -- Analyse -- Périodiques; Hygiène alimentaire -- Périodiques; Food -- Analysis; Food handling; Food -- Quality; Periodicals; Electronic journals; 664.07
• DOI: 10.1016/j.foodcont.2015.03.034
• Languages: English
• ISSNs: 0956-7135

Abstract

Abstract: From 26 October 2013 to 23 April 2014, 32 cases of listeriosis infected with an Listeria monocytogenes strain serovar 4b, sequence type 4 and belonging to a single distinct PFGE pulsotype were registered in patients from several cantons of Switzerland. L. monocytogenes was detected in blood (75%), CSF (16%), ascites (6%) and in joint fluid (3%) samples. By the end of March 2014, a food producing company reported an L. monocytogenes contamination of ready-to-eat salads to the authorities after detecting the pathogen through its in-house routine quality control. Product and environmental samples collected during subsequent investigations yielded isolates, matching the outbreak strain, thus confirming that ready-to-eat salad from this company was most likely the outbreak source. The cause for the product contamination was related to a design-inherent hygienic problem of one specific product-feeding belt. Complementary patient interviews also identified ready-to-eat green salads bought at one retailer as the likely outbreak source. Highlights: From 32 cases of listeriosis a strain with a distinct PFGE pulsotype was isolated. An L. monocytogenes strain of serotype 4b, ST4 was responsible for the outbreak. Product and environmental samples yielded isolates matching the outbreak strain. A design-inherent hygienic problem of a specific product-feeding belt was the cause.