Shiga Toxin-producing Escherichia coli (STEC)
2014 Case Definition

Background

Shiga-toxin producing Escherichia coli (STEC) can cause illness that ranges from mild diarrhea to bloody diarrhea, and life-threatening hemolytic uremic syndrome (HUS). STEC are categorized into serogroups by their somatic O antigen. The STEC serogroup most commonly identified and associated with severe illness in the United States is E. coli O157; however, there are over 50 other serogroups that can cause illness.

Clinical Description

An infection of variable severity characterized by diarrhea (often bloody) and abdominal cramps. Illness may be complicated by Hemolytic Uremic Syndrome (HUS). (Note, some clinicians still use the term thrombotic thrombocytopenic purpura [TTP] for adults with post-diarrheal HUS.); asymptomatic infections also may occur, and the organism may rarely cause extraintestinal infections.

Laboratory Criteria For Diagnosis

Laboratory confirmed

• Isolation of STEC from a clinical specimen. Escherichia coli O157 isolates that produce the H7 antigen may be assumed to be Shiga toxin-producing. For all other E. coli isolates, Shiga toxin production or the presence of Shiga toxin genes must be determined to be considered STEC.
• Both asymptomatic infections and infections at sites other than the gastrointestinal tract, if laboratory confirmed, are considered confirmed cases that should be reported.

Supportive laboratory results

• A case with isolation of E. coli O157 from a clinical specimen, without confirmation of H antigen or Shiga toxin production
• Identification of an elevated antibody titer to a known STEC serotype from a clinically compatible case
• Identification of Shiga toxin in a specimen from a clinically compatible case without the isolation of STEC

Epidemiologic Linkage

A clinically compatible case that is epidemiologically linked to a confirmed or probable case.

Suspected

• A case of postdiarrheal HUS (see HUS case definition) OR
• Identification of Shiga toxin in a specimen from a clinically compatible case without the isolation of STEC

Probable

• A case with isolation of E. coli O157 from a clinical specimen, without confirmation of H antigen or Shiga toxin production. OR
• A clinically compatible case who is a contact of an STEC case or is a member of a defined risk group during an outbreak. OR
• Identification of an elevated antibody titer to a known STEC serotype from a clinically compatible case

Confirmed

• A case that meets the confirmed laboratory criteria for diagnosis. When available, O and H antigen serotype characterization should be reported.

• Shiga Toxin-producing Escherichia coli (STEC) | 2018 Case Definition
• Shiga Toxin-producing Escherichia coli (STEC) | 2006 Case Definition