Reduction of Shiga toxin-producing Escherichia coli attached to stainless steel

Amy R. Parks and Mindy M. Brashears write in Food Safety Magazine that shiga toxin-producing Escherichia coli (STEC) are pathogens of concern across various products within the food industry, as they have been connected to a wide variety of outbreaks and recalls.

e.coli.vaccine.beefMost of the scientific literature concerning the removal of attached STEC cells focuses on E. coli O157:H7, as it was the first STEC to be considered an adulterant in nonintact beef products in the United States after a large outbreak from undercooked ground beef patties in 1982.

Worldwide, non-O157 STEC strains are estimated to cause 20 to 50 percent of STEC-related infections. A review of outbreaks from 1983 through 2002 found six serogroups (O26, O111, O103, O121, O145 and O45) to be the most common non-O157 STECs causing human illness in the United States.With an estimated 70 percent of non-O157 STEC infections being caused by these serogroups, the U.S. Department of Agriculture Food Safety and Inspection Service has included these serogroups along with E. coli O157:H7 as adulterants in nonintact beef products.

Biofilms are communities of microorganisms that can form on both living and nonliving surfaces, including those found in food processing plants. Biofilm formation depends on the microorganisms present and can be affected by a variety of environmental conditions, including nutrient availability, temperature, the cleanliness of the surface and the presence of other microorganisms. Previous studies have determined that E. coli O157:H7 can attach and form biofilms on surfaces such as stainless steel and plastic.

A series of studies, including two conducted in our laboratory, have shown STEC attachment is strain dependent. This finding was important because it shows assumptions cannot be made about the entire serogroup in terms of attachment to and biofilm formation on these surfaces.