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Shiga toxin-producing E. coli (STEC)

Shiga toxin-producing Escherichia coli (STEC) is a reportable disease in Oklahoma.  E. coli are among the most common bacteria found in the digestive tracts of humans and animals.  While most strains of the bacteria are harmless, some strains have developed the ability to produce a toxin that can cause serious disease in humans.  STEC including E. coli O157:H7 and other Non-O157:H7 strains such as O111, O26 and others can cause mild to severe diarrhea.  In 1982, an unusual strain of E. coli (E. coli O157:H7) was identified as the cause of an outbreak of bloody diarrhea in the United States.  E. coli O157:H7 is the most common of several strains of the toxin-producing bacteria called STEC.

E. coli O157:H7 and other STEC bacteria live in the digestive tracts of cattle and possibly other animals such as deer.  Humans can become infected with the bacteria following direct or indirect contact with cattle feces.  Indirect contact with the feces from cattle often results from eating contaminated foods. Serious outbreaks and deaths due to STEC have occurred in the U.S. resulting from undercooked ground beef, especially hamburgers.  In addition, outbreaks have been linked to produce (melons, lettuce, coleslaw, and alfalfa sprouts), unpasteurized raw milk or juice, contaminated drinking or recreational water, and exposure to animals at petting zoos.  The bacteria may also be spread from one person to another through feces, particularly within families, childcare centers, and other institutions.

The STEC bacterium causes diarrhea that is often bloody and accompanied by abdominal cramps, but fever is absent or mild.  The illness typically resolves within a week.  Unfortunately, about eight percent of individuals that experience symptoms due to STEC will develop hemolytic uremic syndrome (HUS). Persons who develop HUS may experience short-term kidney failure.  However, some persons may develop long-term kidney failure, seizures, stroke, and damage to the bowel.

An estimated 2,100 hospitalizations and 61 deaths due to STEC occur annually in the U.S.  Children under 5 years old are most frequently diagnosed with illness caused by STEC and are at greatest risk of developing HUS.  The elderly also appear to be at increased risk of complications.

Most persons with disease caused by STEC will recover without antibiotics or other specific treatment within 5 to 10 days.  There is no evidence that antibiotics improve the course of disease.  Also, reasonable concern exists that some antibiotics may actually increase the risk of developing HUS. Antidiarrheal agents, such as loperamide (Imodium), should also be avoided.  Health care providers may recommend an increased intake of fluids to prevent dehydration from STEC associated diarrhea.  HUS is a life-threatening condition requiring hospitalization and treatment in an intensive care unit.  Treatment for HUS often requires blood transfusions and kidney dialysis.  Approximately three to five percent of persons who develop HUS will die despite treatment in intensive care.

Laboratory testing for the most common STEC, E. coli O157:H7, typically consists of identifying the bacteria in the stool of ill people.  Most laboratories that culture stool do not routinely test for E. coli O157:H7, so it is important for health care providers to request that the stool specimen be tested on sorbitol-MacConkey (SMAC) agar for this bacteria.  Commercial tests that can detect the toxin released by STEC bacteria have also been developed and should be included when a STEC is suspected.  Persons who experience bloody diarrhea should seek medical attention and have their stool tested for STEC in addition to other enteric pathogens.

OSDH Advises Consumers to Not Eat Romaine Lettuce

The Oklahoma State Department of Health (OSDH) and the Centers for Disease Control and Prevention (CDC) are advising consumers not eat any romaine lettuce at this time due to potential E. coli contamination.  CDC, public health and regulatory officials in several states, Canada, and the U.S. Food and Drug Admininistration (FDA) are investigating a multistate outbreak of Shiga toxin-producing Escherichia coli O157:H7 (E. coli O157:H7) infections linked to romaine lettuce.

Consumers who have any type of romaine lettuce in their home should not eat it and should throw it away, even if some of it was eaten and no one has gotten sick.  This advice includes all types of romaine lettuce, including salad mixes that contain romaine.  Consumers should also wash and sanitize drawers, shelves, and containers that the romaine was stored. Restaurants and retailers should not sell or serve any romaine lettuce.

According to the latest outbreak information, thirty-two people infected with the outbreak strain of Shiga toxin-producing Escherichia coli O157:H7 have been reported from 11 states.  No cases have been identified in Oklahoma residents.  The Public Health Agency of Canada has also identified 18 ill people in the Ontario and Quebec provinces.  Ill persons in this outbreak have the same DNA fingerprint as the E. coli strain isolated from ill people in a 2017 outbreak linked to leafy greens in the U.S. and to romaine lettuce in Canada. 

For more information on this food safety alert and outbreak, please visit the links below.

STEC Fact Sheets and Information:

STEC Fact Sheet 2014 (206k.pdf)

Hemolytic Uremic Syndrome (HUS) Fact Sheets and Information:

 This Page Last Updated November 21, 2018



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