An outbreak of shiga toxin-producing E. coli in Danish children was traced back to beef sausages using an unusual epidemiological tool: credit card receipts. The case is described in the April 15, 2009 issue of Clinical Infectious Diseases, now available online.
Between February and May of 2007, Danish officials identified 20 genetically related cases of E. coli infection. All cases were relatively mild, and the patients recovered. Interviews with the parents of the sick children didn’t turn up any likely food suspects, so investigators had to try something different. Armed with the parents’ credit card information and a list of supermarkets at which they had shopped, the authors asked the grocery stores to search their central computers for a list of all items purchased by the affected families.
Complete lists of items purchased were obtained for seven families, five of which had purchased a particular brand of fermented, organic beef sausage. A sixth family was linked to the sausage through shopping records from the kindergarten their two affected children attended. Sausages recovered from unopened packages tested positive for the outbreak strain, STEC O26.
The authors say the source of the outbreak would most likely never have been found without credit card and supermarket database information. This is also the first time the outbreak source of the less common E. coli strain O26 has been identified. If diagnostic efforts and quality control programs in food production are focused only on detecting the more common STEC O157 strain, the authors caution, more outbreaks and illnesses are possible.