title: Iceberg lettuce as suggested source of a nationwide outbreak caused by two Salmonella serotypes, Newport and Reading, in Finland in 2008.
abstract: A nationwide outbreak of Salmonella enterica serotypes Newport and Reading occurred between 17 October and 28 November 2008 in Finland. A total of 77 culture-confirmed Salmonella Newport and 30 Salmonella Reading cases, including one case with a double infection, were reported. All strains isolated from the patients were subtyped using serotyping, microbial resistance profiling, and pulsed-field gel electrophoresis (PFGE). Here, the PFGE patterns of the studied Salmonella Newport strains were identical, whereas four different PFGE profiles were found among the Salmonella Reading strains. Two elderly patients died within 2 weeks of the onset of symptoms. Three geographical clusters of cases with an epidemiological link were identified. The traceback investigation suggested that the factor connecting the cases was ready-chopped iceberg lettuce available for mass catering use. However, none of the tested food, environmental samples, or the samples taken from the staff of the processing plant contained Salmonella bacteria. Tracing back to outbreak sources with a short shelf life can be complex.
authors.affiliation: National Institute for Health and Welfare, Department of Infectious Disease Surveillance and Control, Bacteriology Unit, PL 30, 00271 Helsinki, Finland. taru.lienemann@thl.fi
authors.forename: Taru
authors.initials: T
authors.lastname: Lienemann
authors.forename: Taina
authors.initials: T
authors.lastname: Niskanen
authors.forename: Sandra
authors.initials: S
authors.lastname: Guedes
authors.forename: Anja
authors.initials: A
authors.lastname: Siitonen
authors.forename: Markku
authors.initials: M
authors.lastname: Kuusi
authors.forename: Ruska
authors.initials: R
authors.lastname: Rimhanen-Finne
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D004196:Disease Outbreaks; D005260:Female; D005387:Finland / Q000453:epidemiology; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D018545:Lactuca / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D012475:Salmonella / Q000145:classification / Q000302:isolation & purification*; D012478:Salmonella Food Poisoning / Q000453:epidemiology*; D012703:Serotyping; D055815:Young Adult