E. coli O157:H7 Outbreak Linked to Cucumbers (Colorado, 2013)

A 2013 outbreak of  E. coli O157:H7, where 9 individuals were infected, appears to be linked to eating sandwiches containing cucumbers.  All ill patrons ate at different shops of the same restaurant chain which all used the same lot of cucumbers.

From the report:

Prior to this outbreak, there have been no documented E. coli O157:H7 outbreaks associated with cucumbers in the United States, per a literature search conducted by CDPHE and by searching for outbreaks on CDC’s Foodborne Outbreak Online Database (http://wwwn.cdc.gov/foodborneoutbreaks/), which captures foodborne outbreak reports generated by local and state health departments and the CDC from 1998 through 2012. An outbreak of E. coli O157:H7 associated with consumption of cucumber salad (consisting of cucumbers, hard-boiled egg, and vinaigrette dressing) affected school-age children from England who were visiting France in 2002 (5). The investigators hypothesized that the cucumbers became contaminated in the growing field. There is evidence that cucumbers can support the growth of E. coli O157:H7 based on a 1993 study by Abdul-Raouf et al (6). The researchers inoculated sliced cucumbers with E. coli O157:H7 and found that the bacteria load increased when storage temperatures were at 21 degrees Celcius (69.8 degrees Fahrenheit). Mukherjee et al conducted microbiological analyses of fresh cucumbers produced by organic and conventional farmers in Minnesota and were not able to isolate E. coli O157:H7 but did find that cucumbers are often contaminated with coliforms, an indicator of fecal contamination (7).

For this particular investigation, it is not clear how the cucumbers could have been contaminated. It is very unlikely that contamination occurred within the 3 implicated Jimmy John’s locations, as no major food handling violations were noted during the environmental assessments and no ill food handlers were discovered. It is more likely that the implicated stores received contaminated cucumbers. Our investigation found no evidence that would support that the cucumbers became contaminated at the Denver-based produce distributor (Colo-Pac Produce, Inc.) or during shipment to the implicated Jimmy John’s locations. 

But it is easy to see that cucumbers can be a source. They are on the ground when harvested, and if not washed sufficiently, that contamination can be transferred to the slice when cut.
  
  
 Marler Blog / Colorado Department of Public Health and Environment
http://www.marlerblog.com/files/2014/12/CDPHE-Final-Report-Dec.-4-2014.pdf-Adobe-Acrobat.pdf
 Outbreak #2013-00-006 - Escherichia coli O157:H7 Outbreak Associated with Cucumbers Consumed at a Sandwich Restaurant Chain – Colorado, October 2013

Summary
 CDPHE and several Denver metropolitan area public health departments investigated an outbreak of Escherichia coli O157:H7 (E. coli O157:H7) that occurred in October 2013. Nine cases were identified, including 1 probable case and 8 laboratory-confirmed cases with matching pulsed-field gel electrophoresis (PFGE) and multiple-locus variable number tandem repeat analysis (MLVA) patterns from E. coli O157:H7 isolated from stool. All 9 cases reported eating sandwiches at Denver-area Jimmy John’s locations in early October 2013. The outbreak investigation consisted of case finding and interviews, 2 separate case-control studies, environmental investigations, produce traceback, and laboratory testing. The results of this investigation indicate that consumption of Jimmy John’s sandwiches containing cucumbers imported from Mexico was the likely cause of the outbreak. To our knowledge, this is the first E. coli O157:H7 outbreak associated with cucumbers reported in the United States. Public health and food safety officials should be aware that cucumbers may be contaminated with E. coli O157:H7, which could cause sporadic E. coli O157:H7 infections as well as outbreaks. As of the date of this report, no other cases of E. coli O157:H7 with the PFGE pattern combination seen in this outbreak were reported in Colorado.