Multiple outbreaks of Salmonella braenderup associated with consumption of iceberg lettuce

The aim of this study was to describe the findings from an outbreak investigation following several apparently unrelated community outbreaks of gastroenteritis. Epidemiological, environmental, laboratory and traceback investigations were used to identify the source of the outbreak. We enrolled 23 (of 29) laboratory confirmed cases and 24 neighbourhood case-nominated controls in a case-control study which revealed that illness was associated with consumption of iceberg lettuce (matched odds ratio 8.0 (95% CI 1.1-355) contaminated with Salmonella braenderup. Several eating establishments were affected and the lettuce was traced back to a single producer in Spain. This is the first UK report implicating S. braenderup in an outbreak due to lettuce. The results highlight the need to increase attention to the various stages in the farm-to-fork process to reduce produce-associated outbreaks related to the global food trade.