Risk Factors for Non-O157 Shiga Toxin-Producing Escherichia coli Infections, United States

Abstract

Shiga toxin-producing Escherichia coli (STEC) causes acute diarrheal illness. To determine risk factors for non-O157 STEC infection, we enrolled 939 patients and 2,464 healthy controls in a case-control study conducted in 10 US sites. The highest population-attributable fractions for domestically acquired infections were for eating lettuce (39%), tomatoes (21%), or at a fast-food restaurant (23%). Exposures with 10%-19% population attributable fractions included eating at a table service restaurant, eating watermelon, eating chicken, pork, beef, or iceberg lettuce prepared in a restaurant, eating exotic fruit, taking acid-reducing medication, and living or working on or visiting a farm. Significant exposures with high individual-level risk (odds ratio >10) among those >1 year of age who did not travel internationally were all from farm animal environments. To markedly decrease the number of STEC-related illnesses, prevention measures should focus on decreasing contamination of produce and improving the safety of foods prepared in restaurants.

Keywords: Escherichia coli; FoodNet; STEC; Shiga toxin–producing Escherichia coli; United States; animals; bacteria; case-control; enteric infections; food safety; foodborne illnesses; meat; produce; risk.

Figure

Flowchart for inclusion/exclusion in study of risk factors for non-O157 STEC infections, United States. *Campylobacter, n = 11; Salmonella, n = 8; Cryptosporidium, n = 7; STEC O157, n = 7; C. difficile, n = 2; Giardia, n = 2; Cryptosporidium and Giardia, n = 1; norovirus, n = 1; Shigella, n = 1. †An additional 3 infants who traveled internationally were included in the Traveled internationally box above. STEC, Shiga toxin–producing Escherichia coli.