Fourth Sprout

Fourth Sprout-borne Salmonella Outbreak in Finland during the 90's

Ritvaleena Puohiniemi, Tarja Heiskanen and Anja Siitonen

Food Associated Pathogens, Uppsala, Sweden, 6-8 May

1996, P 166-7

Sprouts have become an important cause of outbreaks of food-borne salmonellosis in Finland. In the 90's already four sprout-borne outbreaks have occurred with 100-300 subjectsinfected in each. Both the frequency of outbreaks and the number of people infected have increased. In the 80's there were four sprout-borne Salmonella outbreaks inFinland; the total reported number of infected cases was less than 200 (30-50 in each outbreak).

The latest sprout-borne salmonellosis outbreak started March 1995. During the four month period until June Salmonella Stanley infection was identified in 108 subjects. Many of the patients spontaneouslysuspected that they had been infected from alfalfa sprouts. Stanley is normally a rare serotype in Finland; there are no reports for StanleyinFinnish production animals and less than 10 cases a year have been identified in patients mainly returned recently from abroad before the illness.

All Stanley isolates collected during the outbreak had unique pulsed-field gel electrophoresis (PFGE) pattern (with Xba I) and antibiogram. Incontrast, among the 42 other Stanley isolates both the PFGE patterns and the antibiograms differed. However, attempts to culture Salmonellae from the implicated seeds and sprouts failed.

The outbreak ended after the industrial sprouting of alfalfa seeds was prohibited.

There was a S. Stanleyoutbreak also in the USA at the same time; thesame Dutch shipper had delivered alfalfa seeds to the USA and Finland.

Ritvaleena Puohiniemi

National Public Health Institute

Department of Bacteriology

Laboratory of Enteric Pathogens

Mannerheimintie 166 FIN-00300 Helsinki

Finland

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