I was casually reading my copy of the Journal of Infectious Disease (I know, why not People Magazine) and found this article – “A Novel Vehicle for Transmission of Escherichia coli O157:H7 to Humans: Multistate Outbreak of E. coli O157:H7 Infections Associated With Consumption of Ready-to-Bake Commercial Prepackaged Cookie Dough—United States, 2009.” Since I lived this outbreak (more so my clients – 65 total total sickened with E. coli O157:H7) I read it with interest. Some of the more interesting discussion points were the consumption patterns of consumers, the likely ingredient that was contaminated and what should be done in the future to avoid another outbreak.

19_map.jpgThe investigators found that consumption of cookie dough appeared to be a popular practice, especially among adolescent females. A study of risky eating behaviors among college students revealed that 53% consumed unbaked homemade cookie dough.

Possible means of contamination considered by investigators included introduction of a contaminated ingredient during processing, a lapse in plant biosecurity measures, intentional contamination, or cross-contamination with another food processed in the plant.

• Investigators did not observe any obvious breach in biosecurity that would facilitate introduction of E. coli O157:H7 into the facility from the outside;

• No significant food handling or safety violations were identified at the plant that could result in cross-contamination within the plant;

• Intentional contamination of food with pathogens has been linked to past local, but not national, foodborne outbreaks. Although the possibility of intentional contamination was considered early in the investigation, no evidence of it was found.

A more likely source of contamination was that a contaminated ingredient was used in the product. Ready-to-bake cookie dough is not a ready-to-eat food and contains several ingredients, including flour, pasteurized eggs, chocolate chips, molasses, sugar, margarine, baking soda, and vanillin/vanilla extract.

• The eggs used in brand A products were pasteurized, making eggs a less likely vehicle unless there was a pasteurization failure; this was not identified during the investigation.

• Molasses, sugar, baking soda, and margarine, which undergo pathogen kill steps during processing, were also considered less likely sources of contamination.

• The possibility of contaminated chocolate chips was considered. However, the chocolate chips that company A used in its ready-to-bake cookie dough and the brand A chocolate chips sold to consumers for home baking are manufactured in the same facility, but there was no evidence of an E. coli O157:H7 outbreak among consumers using these chocolate chips.

cookie dough 7.jpgIt was the main ingredient in cookie dough – flour – that caught the eyes of the investigators for a couple of reasons.

• Flour, a raw agricultural product (ie, does not undergo processing to kill pathogens), was also considered as a possible source of contamination.

• Although they found no conclusive evidence that contaminated flour was the source of this outbreak, contaminated flour remains a prime suspect for introducing the pathogen to the product.

So, where do all those college girls eating cookie dough go from here? Several cookie dough manufacturers have advised the FDA that they have implemented the use of heat-treated flour for their ready-to-bake cookie dough products. Foods containing raw flour (not heat-treated) should be considered as possible vehicles of infection of future outbreaks. Food processors should consider the use of pasteurized flour in ready-to-cook or ready-to-bake foods that are likely to be consumed without cooking or baking, even though label statements may warn against consuming uncooked product.