An outbreak that sickened 126 people in Germany and the Netherlands traced to mung bean sprouts was caused by a single strain of Salmonella Newport.
Researchers said to their knowledge, mung bean sprouts had not been described as the infection vehicle in a Salmonella enterica serovar Newport outbreak to date.
It was the largest S. Newport outbreak ever reported in Germany.
The epidemic curve showed a peak from 21 October to 5 November 2011, which suggested an infection vehicle in circulation for a limited time due to a short shelf-life.
Findings demonstrate that consumption of raw or briefly cooked sprouts is associated with a considerable risk of foodborne illness, according to Rosner et al.
25,310 cases of Salmonella infections were notified, with only 83 (0.3%) being caused by S. Newport in 2010 in Germany.
22 (1.5%) of the 1,466 reported infections were S. Newport infections in the Netherlands in 2010.
The outbreak in Germany affected 106 people with a median age of 38 years and 52% of cases were female.
Hospitalisation due to S. Newport infection was reported for 28% of the cases.
In the Netherlands, 20 outbreak-related S. Newport cases were reported with a median age of 37 years and 15 cases were female.
The onset of illness, known for 15 of the Dutch outbreak-related case patients, was between 13 October and 1 November 2011.
Two cases were already hospitalised when developing gastrointestinal symptoms and no information on hospitalisation was available for three cases.
Of the 14 case-patients in Germany who recalled sprout consumption, eight could not name the kind they had eaten, one named mung bean sprouts, four named soybean sprouts, and one named other sprouts.
Ten case-patients remembered that the sprouts had been long and white, the kind of sprouts typically served in Asian restaurants, and eight said that they had been raw (8 people) or only briefly heated (3).
“Comparative molecular typing was instrumental in detecting the outbreak vehicle, as the PFGE pattern of 32 human isolates was indistinguishable from the mung bean sprouts isolate,” said the researchers.
The pathogen had a mean of 113 notified cases per year between 2001 and 2010 with 24 outbreaks in Germany.
The outbreak investigation included an analytical epidemiological study, molecular typing of human and food isolates and traceback investigations.
S. Newport outbreaks in other countries have been linked to food such as ground beef, horse meat, cheese, tomatoes, lettuce, ready-to-eat salad vegetables and alfalfa sprouts.
Mung bean sprouts were suspected as the vehicle because two lots contaminated with an unspecified serovar of Salmonella had been found at a sprout producer in the Netherlands, sampled during the company’s own testing of production batches on 18 and 21 October 2011.
Salmonella Newport had been detected in mung bean sprouts taken during routine sampling at another sprout distributor in northern Germany on 19 October 2011.
“An outbreak of Salmonella Newport associated with mung bean sprouts in Germany and the Netherlands, October to November 2011”
Authors: C Bayer, H Bernard, R Prager, W Rabsch, P Hiller, B Malorny, B Pfefferkorn, C Frank, A de Jong, I Friesema, K Stark, B M Rosner