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E. coli O157:H7

HGIC 3700

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Quick Facts About E. coli O157:H7

Name: Escherichia coli (E. coli) O157:H7
Disease: Hemorrhagic Colitis
Onset: 2 to 5 days

Symptoms: Severe abdominal cramping and diarrhea, which is initially watery but becomes grossly bloody. Occasionally vomiting occurs. Fever is either low-grade or absent. The illness is usually self-limited and lasts for an average of 8 days. Some individuals exhibit watery diarrhea only.

Associated Foods: Raw or undercooked ground beef, raw milk, lettuce, spinach, unpasteurized apple juice or cider, alfalfa and radish sprouts.

Prevention: Cook meat to an appropriate temperature; avoid cross-contamination; use sanitary practices; drink pasteurized milk and juices.

The Organism

The bacterium E. coli O157:H7, also just known as O157, is a rare but dangerous type of E. coli. It lives in the intestinal tracts of mammals and man. Some healthy cattle, deer, sheep and goats carry the bacteria. It can be transferred from animal to animal, animal to man, from animal to man on food, and from person to person through close contact or food. E. coli O157:H7 can survive refrigeration and freezer storage. Thorough cooking to 160 °F is the best safeguard against infection.

The O157 pathogen was recognized in 1982 after the investigation of two outbreaks of a bloody diarrhea syndrome. The outbreaks were traced to undercooked hamburgers served from a fast food chain. Based on a 1999 estimate, 73,000 cases of infection and 61 deaths occur in the United States each year. In the ten CDC Foodborne Diseases Active Surveillance Network (FoodNet) sites (which represent 15% of the U.S. population), there was a 29% decline in E. coli O157:H7 infection from 1996-1998 to 2006. The actual prevalence of the disease may still be underestimated. The organism is difficult to identify if testing is not done during early onset of infection. Individuals with mild cases of illness may not consult a physician, and therefore, the illness goes unreported.

The Disease

The most common symptom of O157 infection is bloody diarrhea. About 10 to 20 percent of patients with bloody diarrhea can develop more severe diseases — hemorrhagic colitis, hemolytic uremic syndrome (HUS) or thrombotic thrombocytopenic purpura (TTP).

Hemorrhagic colitis is characterized by severe abdominal cramps, bloody stools, little or no fever, and evidence of erosion and hemorrhage of the colon. Initial symptoms usually occur two to eight days after ingestion of contaminated food. The illness can last five to ten days and can be severe enough to result in hospitalization.

Less than 10 percent of cases with bloody diarrhea will develop HUS. HUS causes hemolytic anemia (destruction of red blood cells), affects the central nervous system and causes renal (kidney) failure. Renal failure is the most significant symptom of HUS. About half of the HUS patients require dialysis, and 3 to 5 percent of HUS cases are fatal.

TTP has symptoms similar to HUS; however, the most significant is severe neurologic damage. Complications can include seizures, stroke or coma. Renal damage is less severe than with HUS. This disease is primarily found in adults, particularly the elderly. The mortality rate of TTP can be as high as 50 percent.

Infection with E. coli O157:H7 is diagnosed by detecting the bacterium in the stool. About one-third of the laboratories that culture stools do not test for E. coli O157:H7, so it is important to request that the stool specimen be tested on sorbitol-MacConkey (SMAC) agar for this organism. All persons who suddenly have diarrhea with blood should get their stool tested for E. coli O157:H7.

Most persons recover without antibiotics or other specific treatment in 5 to 10 days. There is no evidence that antibiotics improve the course of the disease, and it is thought that treatment with some antibiotics may precipitate kidney complications. Antidiarrheal agents, such as loperamide (Imodium), should also be avoided. Hemolytic uremic syndrome is a life-threatening condition usually treated in an intensive care unit. Blood transfusions and kidney dialysis are often required. With intensive care, the death rate for hemolytic uremic syndrome is 3 to 5 percent.

Persons who only have diarrhea usually recover completely. A small proportion have immediate complications with hemolytic uremic syndrome and lifelong complications, such as persistent kidney failure, blindness, paralysis and the effects of having part of their bowel removed.

High Risk Individuals

Illness from O157 can occur in individuals of any age. Those with the greatest risk include the very young (children under 5 years of age), the elderly (greater than 65 years of age), or those who are immunocompromised or already ill. Individuals with compromised immune systems should consult a physician regarding special food and food safety recommendations.

Food Sources

Undercooked hamburger and roast beef, raw milk, unpasteurized apple juice and cider, contaminated water, venison, lettuce, and spinach have caused outbreaks in this country over the last 10 years.

E. coli O157:H7 can be transmitted through inadvertent contact with fecal matter during processing of animal foods or because of improper food handling. Improper handling may include contamination by infected food handlers who have not effectively washed their hands before touching the food or utensils that come into contact with the food.

Plant foods can become contaminated from fertilization with raw manure, irrigation with contaminated water, or contamination by human or wild animal contact. Some outbreaks have been attributed to contaminated municipal and recreational water. For more information, see HGIC 3517, Safe Handling of Procuce.

Prevention Strategies

The severity of diseases caused by O157, the low infectious doses of the organism, and uncertainties about when O157 enters human foods increase the need for special care in food preparation. It is particularly important not to overlook safe food handling strategies for food products that are consumed uncooked, such as fruits and vegetables.

While E. coli O157:H7 is a contaminant capable of causing severe disease, it can be effectively controlled by thorough cooking. Cook ground meats (beef, pork, veal, lamb) to a uniform internal temperature of at least 160 °F, non-ground meat cuts such as roasts and steaks (beef, veal, lamb) to an internal temperature of at least 145 °F, non-ground pork to 160 °F, and all poultry to 165 °F. Reheat foods to 165 °F. Keep hot foods at or above 140 °F and cold foods at or below 40 °F.

Presently, the best assurance against infection of O157 is preventative measures practiced at home.

• Cook raw hamburger to the proper internal temperature (160 °F). In a restaurant, make sure a hamburger is thoroughly cooked before eating it. If a hamburger is under-cooked, do not be afraid to return it.
• Avoid drinking milk, apple juice or cider that is unpasteurized.
• Wash hands after handling raw meat products to prevent contamination of other foods.
• Wash hands thoroughly and frequently to help prevent person-to-person transmission. This is a particularly important practice to teach children.
• Drink water from appropriate public or well sources, not from untreated streams or lakes.
• Wash fruits and vegetables thoroughly using only clean, drinkable water.
• Carefully follow “keep refrigerated,” “sell by” and “use by” dates.

Latest Findings for Prevention

Microbiological surveys conducted on beef carcasses and ground beef in slaughter and processing plants have shown that very few carcasses are contaminated with O157. However, this is not an absolute assurance of safety for food products. E. coli O157:H7 prevention strategies have been developed and implemented by beef producers, processors and retailers.

The Hazard Analysis Critical Control Point (HACCP) system is a means for developing food safety programs. This system consists of identifying hazards that can create food safety problems and developing steps to prevent, control or eliminate these hazards in each phase of the food production process. The Food Safety and Inspection Service (FSIS) of the United States Department of Agriculture (USDA) has established new requirements for slaughter and processing plants in the United States. Plants implemented HACCP systems over the three-year period from 1998-2000.

Many decontamination processes have been developed for beef carcasses and are being established in beef processing plants. These processes include carcass washing with organic acid, steam vacuuming, steam pasteurization, and the use of antimicrobial agents. One or more methods to reduce microbial contamination are used on a majority of beef carcasses. The Food and Drug Administration (FDA) has approved irradiation (cold pasteurization) of beef for pathogen reduction. Other sources of O157 infection are not affected by these efforts. Continuing vigilance and safe food preparation must be practiced.

Resources

For Further Information on E. coli, Contact:

USDA Meat and Poultry Hotline
Monday - Friday, 10 a.m. – 4 p.m. ET
(800) 535-4555

Centers for Disease Control and Prevention
Foodborne Illness Information Line
24-hour recorded information
(404) 332-4597

National Cattlemen’s Beef Association (NCBA)
9110 E. Nichols Ave. #300
Centennial, CO 80112
303-694-0305

Questions About E. coli

Is it riskier to eat a rare hamburger than a rare steak or roast?

Yes. Undercooked hamburger is riskier because of the kind of handling and preparation hamburger receives. Surface bacteria may be spread through-out the meat during grinding. Also, ground meat is often made with trimmings from several cuts. This does not mean it is perfectly safe to eat other cuts raw or rare. ALL meat, poultry and fish should be cooked to the correct internal temperature.

How can I tell if the ground beef I buy is safe to eat?

You can’t tell whether ground beef is safe simply by looking at it or smelling it, which is why you should always follow the safe handling recommendations listed here. If an off-odor is apparent, return it to the store.

Does freezing kill E. coli?

No. That’s why it is important to cook all foods thoroughly and follow the safe handling recommendations listed here.

For more information, see HGIC 3517, Safe Handling of Produce.

Sources:

1. Center for Disease Control and Prevention (CDC). Escherichia coli O157:H7. December 2006. http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm
2. International Food Information Council Foundation (IFIC). January 2007. A Consumer’s Guide To Food Safety Risks http://ific.org/publications/other/consumersguideom.cfm
3. U.S. FDA (1992). Bad Bug Book. Escherichia coli O157:H7. http://www.cfsan.fda.gov/~mow/chap15.html