Shiga toxin-producing Escherichia coli (STEC) can be divided into two clinically significant types: those containing the Shiga toxin 2 coding gene (with or without the Shiga toxin 1 coding gene) and those without the Shiga toxin 2 coding gene (i.e., only the Shiga toxin 1 coding gene). Shiga toxin-producing 2 is associated with severe infections, which are characterized by bloody diarrhea and risk of hemolytic uremic syndrome (HUS). Escherichia coli O157:H7 almost all contain the Shiga toxin 2 coding gene, and only a fraction of non-O157:H7 STECs contain the Shiga toxin 2 coding gene. We refer to these STECs that produce Shiga toxin 2 collectively as "high-risk STECs".
Clinical features
High-risk STEC infections exhibit a highly patterned course with a series of events occurring one after another. The first day of diarrhea is considered the first day of illness. Diarrhea is initially non-bloody, but most patients develop macroscopic bloody diarrhea after 1 to 3 days. Patients often have abdominal pain. Although many patients complain of fever early in the disease (i.e., before presentation), fever is rarely present at presentation. If HUS occurs, it is usually diagnosed on days 5 to 13 of illness.
Assessment and diagnosis
Clinical suspicion
The possibility of high-risk STEC infection should be considered in all patients presenting with acute bloody diarrhea and abdominal tenderness, regardless of age. High-risk STEC infection should also be suspected in patients with diarrhea after exposure to a person with known STEC infection, as well as in patients with HUS (even in the absence of diarrhea). Fever does not exclude the possibility of STEC infection.
Microbiological diagnosis
Rapid, accurate, and complete microbiological diagnosis is essential for the detection of STEC infection. We suggest testing STEC with a rectal swab specimen unless the patient is able to provide a stool specimen immediately. Patients with acute diarrhea can be diagnosed with high-risk STEC infection if Escherichia coli O157:H7 is isolated by selective culture or if Shiga toxin 2 (or the gene encoding Shiga toxin 2) is detected. While many molecular tests are able to distinguish between Shiga toxin 1 and 2, test reports do not necessarily provide these details and must be specifically requested.
dispose
Our focus in managing patients with suspected or confirmed high-risk STEC infection is to reduce the risk of HUS, particularly anuriic HUS. We support the admission of such patients for aggressive intravenous fluid management and daily reassessment.
Liquid Management
For patients with suspected or confirmed high-risk STEC infection, we suggest early intravenous volume expansion with isotonic crystalloid with the goal of reducing hemoglobin concentrations. Usually at least 20 mL/kg of normal saline is given quickly, followed by 2 L/m2 daily. The decision to discontinue intravenous fluids depends on the stage of disease, the platelet count shown on daily monitoring, and the clinical picture.
Avoid harmful interventions
We recommend against the use of antibiotics to treat patients with confirmed high-risk STEC infection. We also do not use empiric antibiotics to treat patients with suspected STEC infection while awaiting results of microbiological tests. If STEC is detected after initiation of empiric antibiotic therapy, antibiotic therapy is discontinued. Antibiotic therapy does not reduce symptoms or complications of STEC infection and is associated with the development of HUS.
Infection control
In hospitalized patients with STEC infection, contact precautions should be taken to reduce human-to-human transmission. It should be reported to the local public health department. A negative stool culture is often required before returning to daycare, school, or other sensitive settings (eg, food preparation work).