Escherichia coli O157:H7 outbreak linked to salami, British Columbia, Canada, 1999

An outbreak of E. coli O157:H7 infections was identified in November 1999 with a fivefold increase in the occurrence of laboratory-confirmed cases of E. coli O157:H7 infection. A matched case-control study was conducted. Samples of food from cases and from retailers were analysed for the presence of E. coli O157:H7. A total of 143 cases were identified over a 12-week period with the same pulsed-field gel electrophoresis (PFGE) pattern. The case-control study found that Company A salami was significantly associated with illness (Mantel-Haenszel matched odds ratio 10.0, 95% CI 1.4-434, P=0.01). Company A salami tested positive for E. coli O157:H7 and isolates had the same PFGE pattern as case isolates. An immediate voluntary national recall of Company A dry fermented meat products took place. Findings from the investigation of this outbreak suggest that the hold-and-test option may not be adequate to prevent shiga-toxigenic Escherichia coli (STEC) infection in salami consumers.