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Shiga Toxin-producing e. coli (STEC) INFECTION

Information for Health Professionals

Shiga toxin-producing Escherichia coli (STEC) are important enteric bacterial pathogens in the United States, causing an estimated 265,000 infections, 3,600 hospitalizations, and 30 deaths each year. STEC produce Shiga toxin 1 and/or Shiga toxin 2, potent toxins responsible for many of the pathogenic effects of STEC infection.
STEC O157 is the most widely recognized serogroup. However, there are numerous other STEC serogroups, often referred to collectively as STEC non-O157, that can cause illness similar to O157.

STEC is transmitted by exposure to the feces of a shedding animal or infected human. Acute illness, usually gastroenteritis, typically occurs after an incubation period of 3 to 4 days but may occur anywhere from 1 to 10 days after exposure. Illness may be more severe in young children and older patients. About 5-10% of STEC case-patients develop hemolytic uremic syndrome (HUS), a potentially life-threatening complication of a STEC infection. HUS is a disease characterized by hemolytic anemia, acute kidney failure, and often a low platelet count, and is the leading cause of short-term acute renal failure in U.S. children.

Antibiotics are generally not recommended for the treatment of STEC infection, as some studies have found an association between the use of antimicrobials and the development of HUS. To aid in proper management of STEC infection:

  • Patients should be educated regarding prevention of further spread of STEC by effective hand washing, particularly after using the toilet, changing diapers, contact with farm animals and their environments, and before preparing or eating food.

    • The importance of proper hygiene must be stressed, as excretion of the organism in stool may persist for several weeks after the resolution of symptoms, particularly in children.

  • Patients should be instructed to monitor for signs and symptoms of HUS in the weeks following the onset of diarrhea.

  • Patients should also be asked to recall everything they ate and did during the seven days prior to illness onset. This information may help public health investigators solve outbreaks.

    • High-risk exposures for STEC include consumption of raw or undercooked beef products, unpasteurized milk or dairy products, and unpasteurized juices (including apple cider), as well as contact with livestock, untreated recreational water, and other persons actively infected with STEC.

Key Points

  • It is crucial that all stool specimens collected from patients with symptoms consistent with acute bacterial enteritis be tested for the presence of Shiga toxin and for STEC culture to be attempted.

  • Antibiotics are generally not recommended for patients with STEC infection. Some studies have shown that administering antibiotics to patients with STEC infection might increase their risk of developing HUS, and a benefit of treatment has not been clearly demonstrated.

  • Progression to HUS occurs on average 7 days after symptom onset and may be delayed until after the STEC infection has cleared. Therefore, patients with STEC infection should be monitored for the development of HUS.

Diagnosing STEC infection requires testing a stool specimen. The test can be a culture that isolates the bacteria or a culture-independent diagnostic test (CIDT) that detects genetic material of the bacteria or presence of Shiga toxin 1 and/or 2. Stool culture is required for confirmatory testing and allows for serogrouping and molecular characterization, which is key in the case of a suspected outbreak, and is the preferred method of identifying STEC.

Healthcare providers are required to report cases of STEC infection to the local health department (LHD) within one working day of identification or immediately by telephone if an outbreak of STEC or case of post-diarrheal HUS is suspected. In addition, LHDs may need to restrict the activities of persons with STEC infection from certain work or activities (such as food handling, health care, or day care) until they have been examined and cleared by their LHD.

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