A nationwide outbreak of Salmonella Newport associated with mung bean sprouts
A nationwide outbreak of Salmonella Newport associated with mung bean sprouts,Germany 2011Christophe Bayer (Robert Koch-Institute, Germany), Rita Prager (Robert Koch Institute, Germany), Wolfgang Rabsch (Robert Koch Institute, Branch Wernigerode, Germany, Germany), Petra Hiller (Federal Institute for Risk Assessment, Berlin, Germany), Burkhard Malorny (Federal Institute for Risk Assessment, Berlin, Germany), Beatrice Pfefferkorn (Federal Office of Consumer Protection and Food Safety, Berlin, Germany), Bettina Rosner (Robert Koch Institute, Germany)BACKGROUND: The number of reported Salmonella Newport infections in Germany increased from an average of 2-3 cases per week (2001-2010) to 67 in week 43/2011. As mung bean sprouts contaminated with S. Newport had been detected at a distributor in Lower Saxony we tested the hypothesis of sprouts being the infection vehicle in this outbreak. METHODS: We compared all notified adult S. Newport cases with disease onset between 20/10/2011 and 08/11/ 2011 with S. Enteritidis cases of the same age group (18-31, 32-48 and 49-88 years) notified in October-November 2011 regarding their food consumption, in particular sprouts, in the 3 days before illness. We calculated attack rates and odds ratios (OR) for different foods and performed multivariable analysis to correct for multiple exposures. S. Newport isolates from case-patients and food samples were subtyped by molecular methods. We conducted trace-back investigations for sprouts from locations where cases had eaten.RESULTS: Median age of cases (n=106) was 38 years (range 0-91 years), 52% were female. Sprouts had been consumed by 14/50 S. Newport and 1/45 S.Enteritidis cases (OR=21.2, 95%-CI 2.9 ] 917.9) and showed the highest association amongst identified risk food items in univariate analysis. In multivariable analysis only sprout consumption was associated with S. Newport infection (OR=18.7; 95%CI 2.3-150.2). Molecular subtyping patterns of human isolates were indistinguishable from the mung bean sprouts isolate. Sprouts were traced back to various distributors and a sprout producer in the Netherlands. CONCLUSIONS: Epidemiological, laboratory and trace back evidence point to sprouts as the vehicle of infection. Since sprouts are known to be frequently contaminated with microorganisms, consumption of raw sprouts may impose a health risk.