Escherichia coli (E. coli) Preventive Controls Fact Sheet for Growers and Industry

A 3iVerify fact sheet to help understand preventive controls.

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Most E. coli bacteria are harmless, but some produce a toxin (Shiga toxin) that can cause serious illness, including bloody diarrhea, blood‐clotting problems, kidney failure and death. Not all of the Shiga‐producing E. coli can cause these problems but the subset called enterohemorrhagic E. coli (EHEC) can.

You might have heard news reports about these EHEC bacteria, such as E. coli O157:H7, when they’ve caused outbreaks of foodborne illness. EHEC outbreaks have been traced to many kinds of foods; for example, ground meats, unpasteurized (“raw”) milk, unpasteurized fruit juice, lettuce, spinach, sprouts, and, more recently, commercially manufactured frozen cookie dough.

Some people get the less serious form of the infection which can range from no symptoms to diarrhea, that starts out watery, then turns bloody. But the infection sometimes progresses into the life‐threatening form of the illness that causes kidney failure and other problems, with children and people with weak immune systems being at especially high risk. Cooking ground beef well; washing raw fruits and vegetables under clean, running water and not drinking unpasteurized (“raw”) milk, or eating certain cheeses made from it, are some of the things that consumers can do to minimize risks of infection.

A recent example of E. coli infection, initially thought to be connected with cucumbers, is the large outbreak in 2011 that was centered in Germany, but also affected various other countries in the European Union. The source was later thought to be bean sprouts. The pathogen was identified as an E. coli strain of serotype O104:H4 that produced Shiga toxin and, therefore, was thought to be an EHEC. Although O157:H7 is currently the predominant strain and accounts for approximately 75% of the EHEC infections worldwide, other non-O157 EHEC serotypes are emerging as a cause of foodborne illnesses. In the U.S. a group often referred to as the “big 6” (O111, O26, O121, O103, O145 and O45) accounts for the majority of the non-O157:H7 serotypes isolated from clinical infections and, therefore, is currently a focus of concern. However, other EHEC serotypes such as O113, O91 and others, can also cause severe illness. As a result, the non-O157 EHEC serotypes of public health concern can change quickly, depending on outbreak incidents, and can vary with countries and geographic regions.E.coli keeps on cropping up on all types of food and it is deadly, particularly to the very young and the very old. People who contract E. coli infections often experience life changing complications such as kidney failure, leaving them subject to kidney dialysis to keep them alive and dependent on kidney transplantation to live a near normal life in future.

Susceptible Populations:

All people are believed to be susceptible to hemorrhagic colitis but young children and the elderly are more susceptible and at higher risk for the illness to progress to more severe complications. Others with weak immune systems are also at risk, such as people with some chronic diseases and HIV or AIDS and people on immunosuppressive medications; for example, some drugs used for arthritis and cancer chemotherapy.

About E. coli:

Like generic E. coli, toxin-producing Shiga-toxigenic Escherichia coli (STEC) are Gram-negative, rod shaped bacteria but are characterized by the production of Shiga toxins (Stx).

Depending on the reference cited, there are 200 to 400 STEC serotypes, many of which have not been implicated in human illness. However, a subset of STEC, called enterohemorrhagic Escherichia coli (EHEC), the topic of this fact sheet, includes only those that cause serious illness. Serotype O157:H7 is the prototypic EHEC strain.

Source: FDA Bad Bug Book

The table below gives an overview of the organism, its impact on humans, along with sources and the controls usually employed to prevent illness. This information may be used in growing and food processing operations as part of a HACCP food safety plan or preventive controls food safety plan.

EHEC Infection

General: Most E. coli bacteria are harmless, but some produce a toxin (Shiga toxin) that can cause serious illness, including bloody diarrhea, blood‐clotting problems, kidney failure and death. Not all of the Shiga‐producing E. coli can cause these problems but the subset called enterohemorrhagic E. coli (EHEC) can.

There are about 63,000 cases of EHEC infections in the U.S. yearly, according to a report by the Centers for Disease Control and Prevention (CDC). Ground beef and beef products continue to be implicated in most infections; however, contaminated produce increasingly has been implicated as a vehicle.

Caused by: Escherichia coli O157:H7
Mortality: Patients whose illness progresses to HUS have a mortality rate of 3% to 5%
Onset: Symptoms usually begin 3 to 4 days after exposure but the time may range from 1 to 9 days.
Infective dose: The infective dose of EHEC O157:H7 is estimated to be very low, in the range of 10 to 100 cells. The infective dose of other EHEC serotypes is suspected to be slightly higher.
Symptoms: Hemorrhagic colitis is characterized by severe cramping (abdominal pain), nausea or vomiting and diarrhea that initially is watery, but becomes grossly bloody. In some cases, the diarrhea may be extreme, appearing to consist entirely of blood and occurring every 15 to 30 minutes. Fever typically is low-grade or absent.
Duration: In uncomplicated cases, duration of symptoms is 2 to 9 days, with an average of 8 days.
Complications: Infections from EHEC may range from asymptomatic-to-mild diarrhea to severe complications. The acute symptoms are called hemorrhagic colitis (HC), characterized by severe abdominal cramps and bloody diarrhea, which may progress to such life-threatening complications as HUS or thrombotic thrombocytopenia purpura (TTP) – conditions that are most often associated with O157:H7 but that also can occur with other EHEC serotypes. About 3% to 7% of HC cases progress to HUS or TTP. Some evidence suggests that Stx2 and intimin are associated with progression to severe disease, such as HUS. Kidney cells have a high concentration of Stx receptors; hence, the kidney is a common site of damage. Some survivors may have permanent disabilities, such as renal insufficiency and neurological deficits. Antibiotic therapy for EHEC infection has had mixed results and, in some instances, seems to increase the patient’s risk of HUS. One speculation is that antibiotics lyse EHEC cells, releasing more Stx into the host.
Route of entry: Oral (e.g., ingestion of contaminated food, water, or fecal particles).
Pathway: After ingestion, EHEC attaches to intestinal epithelial cells via LEE-encoded factors and produces Stx that are internalized, activated and can pass into the bloodstream to become systemic.
Implicated foods: Raw milk, inadequately pasteurized milk, chocolate milk, cheeses (particularly soft cheeses), ice cream, raw vegetables, raw poultry and meats (all types), fermented raw-meat sausages, hot dogs and deli meats and raw and smoked fish and other seafood.

E. coli is a major health problem to humans, it is relatively common compared to other pathogens and continues to occur in different foods over time. This makes E. coli one of the deadliest organisms in food. It has a significant cost to industry and health services and damages high profile food company brands, many of whom struggle to recover from outbreaks. The advent of social media means that food companies have nowhere to hide and are easily exposed for the lack of controls they have in place. This means that food businesses must be extra vigilant with respect to the preventive controls in place in their food processing and storage operations. Increased oversight over the preventive controls in their supply chains is critical to prevent illness and operate a profitable and sustainable food business.

Sources of E. coli:

Raw or undercooked ground beef and beef products are the vehicles most often implicated in O157:H7 outbreaks. Other outbreaks involved the consumption of raw milk. O157:H7 can develop acid tolerance, as evidenced by infections in which acid foods (pH<4.6) have been implicated, such as yogurt, mayonnaise, fermented sausages, cheeses and unpasteurized fruit juices. Various water sources, including potable, well, and recreational water, have also caused EHEC infections, as has contact with animals at farms or petting zoos. Produce, including bagged lettuce, spinach, and alfalfa sprouts are increasingly being implicated in O157:H7 infections. Interestingly, infections in the U.S. by non-O157:H7 EHEC, has been caused by many of these same vehicles, but, as of this writing, beef products have seldom been implicated. Person-to-person transmission of infection is well documented. Additional information is available from “Escherichia coli Serotype O157:H7: Novel Vehicles of Infection and Emergence of Phenotypic Variants,” by Dr. Peter Feng, FDA. Emerging Infectious Diseases (1995) 1(2)

E. coli in Food

Although E. coli is traditionally associated with meat products, fresh produce has also been implicated regularly in recent years. The organism continues to cause food safety problems in a wide variety of foods due to its low infective dose and poor personal hygiene of food operators.

Foods linked to E. coli:

Raw or undercooked ground beef, beef products, raw milk, cheeses, unpasteurized fruit juices, bagged lettuce, spinach, alfalfa sprouts, bean sprouts, fresh vegetables from contaminated sources

The reason that so many foods can become contaminated or adulterated with E. coli is down to the fact that it has such a low infective dose. This allow even small numbers of the organism to easily cause infection in cooked and ready to eat foods. This means that the two main controls are prevention of cross contamination in the first place and proper cooking to destroy any viable cells in contaminated food.

Cross Contamination:

Cross contamination occurs when E. coli is spread from a contaminated source, such as contaminated foods, people or water, to other foods or objects in the environment. An example of how this may occur is when potentially contaminated dairy products, fresh produce or seafood are not kept separate from each other during preparation or cooking, or when a food handler does not adequately clean utensils, surfaces, equipment and hands after they have come into contact with these products or have used the toilet. The contamination can spread to factory and equipment surfaces, as well as kitchen surfaces and utensils. Cross contamination may occur at any point in the food process. Cross contamination may also occur from handling contaminated foods, then handling food, food-preparation utensils, or other objects in the environment.

Limiting Conditions (including kill temperatures):

The following table gives the conditions that can be used to limit the growth of E. coli.

Environmental Condition

Minimum

Optimum

Maximum

Growth temperature 44oF / 6.5oC 95-104oF / (35-40oC) 121oF / 49.4oC
pH 4 6-7 10
Water activity (aw) 0.95 0.995 N/A
Max % water phase salt N/A N/A 6.5

Kill temperatures for E. coli include heating to:

  • 162 oF (72oC or greater) for 1 minute or equivalent

Please note that recent research indicates speed of temperature increase is important. A slow rise in cooking temperature may lead to E. coli becoming more temperature resistant, in which case it may require higher temperatures to reach a kill temperature.

When it comes to killing micro organisms, both temperature and time determine the effectiveness of the result. In addition, the kill temperatures must be measured in the center of the food product to ensure the minimum core temperature required for organism death is achieved.

Preventive Plan Assessment:

When reviewing a preventive plan for any of the affected foods above (or any food that could come into contact with E. coli contaminated sources) the key controls you must look for may include the following:

  • Water Sources: Prevention of use of sewage contaminated water sources for irrigation, washing or processing, only potable water sources are to be used.
  • Other Food Sources: Prevention of cross contamination from potential E. coli sources (such as water, unpasteurized dairy products, raw meat, raw fish and fresh produce sources) to food, ingredients and food processing surfaces or equipment.
  • Cleaning Program: Ensure that cleaning procedures, which involve high pressure cleaning techniques, are properly risk assessed and scheduled to minimize aerosolization. For example, floors and drains are cleaned using sanitizers and low-pressure techniques, food contact surfaces are sanitized after all floors and drains have been cleaned, or food room fogging sanitation takes place after all other cleaning.
  • Food handlers: Exclusion of food handlers who have recently been sick.
  • Medical Testing: Medical testing of food handlers who have been sick before allowing return to work to prevent human cross contamination.
  • Kill Temperatures: For cooked and ready to eat foods, which have a thermal processing, ensure that adequate temperature controls are in place and that kill temperatures are being achieved.
  • Preventive Controls: For ready to eat foods that do not have a thermal processing step, ensure that rigorous prevention controls are in place and that regular E. coli testing takes place.
  • Packaging Integrity: For raw foods, intended to be cooked by the consumer or further processed, ensure that packaging is secure and leak proof so that other foods are not contaminated.
  • Cooking Instructions: For raw foods, intended to be cooked by the consumer or further processed, ensure that clear cooking instructions are given to consumers including, in the case of meats, the instruction not to wash the meat before cooking (this spreads Bacteria in their kitchen / processing area). Also, ensure that the correct cooking times and temperatures are clearly displayed on the product label cooking instructions.

We hope this E. coli Prevention Fact Sheet has been informative and can be used to help you assess the safety of foods that you purchase from suppliers or process. The team at 3iVerify are highly experienced and qualified food safety consultants.

Our 3iVerify solution can help take the time, hassle and risk out of risk assessing your suppliers and reduce the risk of your company falling foul of E. coli and other food safety risks. If would like to know more about how 3iVerify can help you reduce risks, save time and prevent food borne illness and brand damage, or you have any questions regarding the above, please feel free to contact us.