Non-O157:H7 Shiga Toxin-Producing E. coli

Producing the safest meat and poultry possible is the industry’s number one priority.  Federal inspectors are present in meat plants every day to ensure that the plants comply with federal food safety rules and that the technologies used to destroy bacteria are working to ensure that only safe and wholesome products enter the marketplace.

The meat and poultry industry has been studying the issue of Shiga toxin-producing Escherichia coli or STEC for more than a decade.  Plants have implemented food safety interventions that have enhanced food safety.  Beef produced in the United States is safe and getting safer.  However, some have expressed concern about another type of bacteria: non-O157:H7 Shiga toxin-producing E. coli.

What is Shiga toxin-producing Escherichia coli?

Generic Escherichia coli (E. coli) bacteria are an essential, but normally harmless, component of the digestive tract of healthy animals and people.  Some forms of E. coli, however, can cause disease by making a toxin known as “Shiga toxin.”  The bacteria that make these toxins are known as “shiga toxin-producing E. coli,” or STEC.  The term “enterohemorrhagic E. coli” or “EHEC” also refers generally to this same group of bacteria.

The most commonly identified STEC is E. coli O157:H7, a virulent strain of the family of generic E. coli bacteria that is found in cattle, deer and other warm-blooded animals.  If E. coli O157:H7 is found in “non-intact beef products” like ground beef, the product cannot be sold, and if the product has entered the marketplace, it must be recalled

Thanks to the many modern food safety technologies used by the meat processing industry, E. coli O157:H7 is reduced dramatically during the processing of cattle and government data show that it is found in less than one quarter of one percent of ground beef samples tested by the U.S. Department of Agriculture (USDA).

In addition to E. coli O157:H7, other kinds of STEC, called serogroups, can cause disease.  These serogroups are sometimes referred to as “non-O157:H7 Shiga toxin-producing E. coli”  and have been the recent focus of regulators and researchers.

Background on non-O157 STEC

The potential for non-O157 STEC to cause foodborne illness has been long recognized.  In 2000, the Centers for Disease Control and Prevention (CDC) made non-O157 STEC a reportable disease, and CDC has been tracking illnesses and outbreaks since that time.  Since then, there has been only one outbreak of human non-O157 illnesses associated with non-O157 on a beef product.

In September 2011, FSIS announced that starting in March 2012, these six additional strains of non-O157 STEC (O26, O111, O103, O45, O145 and O121) would be considered adulterants, along with  E. coli O157:H7, in non-intact beef products like ground beef.

The public health risks of non-O157 STEC

Experts at USDA have said in public meetings that the food safety systems now in place in the U.S. meat and poultry industry work equally well for all STEC, — both non-O157 and O157:H7.  Meat and poultry scientists continue to research and develop new intervention technologies to improve the food safety of beef products.  In fact, emerging research has demonstrated that the same technologies used by the beef industry to prevent and reduce E. coli O157:H7 contamination are also effective against non-O157 STEC.

According to CDC FoodNet data the incidence of foodborne illness for non-O157 STEC in 2011 occurred at a low rate of 1.08 cases per 100,000 people.  This data estimates the non-O157 STEC risk for all foods, not just from beef products.

Consumers should be assured that the highly effective food safety interventions currently in place to control E. coli O157:H7 will also control non-O157 STEC.

In fact, government estimates show that three illnesses per 100,000 people occur each year from the consumption of nearly 10 billion pounds of ground beef.  That is an occurrence of one illness per every five million servings of ground beef, which is far lower than many other foods we consume.

While it is rare for both E. coli O157:H7 and non-O157 STEC to find their way into beef products, it can occur, making careful handling and thorough cooking critical steps consumers can take to add extra insurance that they are consuming a safe product.  Ground beef products like hamburgers or taco meat should be cooked to an internal temperature of 160 degrees Fahrenheit.

Illness prevention

The meat and poultry industry has been studying the issue of non-O157 STEC for much of the last decade and has implemented interventions that are designed to work equally well against E. coli O157:H7 as well as non-O157 STEC and other pathogens.

American Meat Institute Foundation (AMIF) actively works with meat companies, government agencies and other stakeholders to investigate ways the meat and poultry industry can produce better, safer products for consumers.

Since 1999, one quarter of the 85 research projects funded by the Foundation have focused on reducing and eliminating E. coli in beef products.  These projects, totaling more than $2 million, have helped to identify new technologies to reduce microbial hazards in beef products and to gain a better understanding of microorganisms in order to select or create effective antimicrobial technologies.

In 2006, the Foundation began to include non-O157 STEC in its research priorities.  This culminated in 2009 with the funding of AMIF’s first research project dealing with meat and non-meat sources of non-O157 STEC, a comprehensive white paper that draws together epidemiological information from the scientific literature and government publications on outbreaks and discusses effectiveness of existing interventions for preventing exposure of humans to pathogenic non-O157 STEC.  AMIF continues to fund and seek additional research in this area.

Advice for consumers

Consumers should follow the safe handling practices detailed on every package of raw meat and poultry and should take special care to cook ground beef products, such as hamburger and meat loaf, to an internal temperature of 160F.  Beef products like steaks or roasts can be cooked to 145 degrees F with a 3 minute rest period.  What is a rest period?  It is the minimum time after you remove the meat product from the heat source (oven, grill, broiler, etc.) before you can eat the product.  Also, temperature should be verified using an instant-read thermometer.

One might wonder why there are two different recommended cooking temperatures.  Whole muscle cuts like steaks and roasts are sterile on the inside.  Cooking the products destroys any bacteria present on the outside of these cuts.  However, when meat is ground, any external bacteria that may be present are distributed throughout the ground product. That is why it is so important to ensure that ground products are thoroughly cooked to 160◦F.

Consumers with food safety questions should visit to learn more about safe food handling, or call USDA’s Meat and Poultry Hotline at 1-888-674-6854.

Helpful links

Third-party experts

Charles Kaspar, Ph.D.
Department of Animal Sciences
Department of Food Microbiology and Toxicology
Food Research Institute
University of Wisconsin–Madison

Catherine Cutter, Ph.D.
Associate Professor and Food Safety Extension Specialist – Muscle Foods
Chair of the Food Safety Impact Group
Pennsylvania State University

Michael Doyle, Ph.D.
Regents Professor of Food Microbiology
Director, Center for Food Safety
Center for Food Safety and Department of Food Science and Technology
University of Georgia