Information for Clinicians

Diagnosis

E. coli infection is diagnosed when the bacteria are identified from the sample of a patient with an acute diarrheal illness.

Testing for STEC

Stool samples should be routinely cultured for E. coli O157 and simultaneously assayed for non-O157 STEC with a test that detects Shiga toxins (or the genes that encode them).

All presumptive E. coli O157 isolates and Shiga toxin-positive specimens should be sent to a public health laboratory for further characterization.

Rapid, accurate diagnosis of STEC infection is important because early clinical management decisions can affect patient outcomes and early detection can help prevent secondary spread.

Testing for other E. coli

Most U.S. clinical laboratories do not use tests that can detect diarrheagenic E. coli other than STEC. Public health laboratories typically test for non-STEC E. coli only during an outbreak of diarrheal illness with an unknown origin.

Treatment

Hydration

Most E. coli infections can be managed symptomatically. Patients with profuse diarrhea or vomiting should be rehydrated.

Evidence from studies of children with STEC O157 infection indicates that early use of intravenous fluids (within the first 4 days of diarrhea onset) may decrease the risk of renal failure.

Antibiotics

Antibiotics used to treat infection with diarrheagenic E. coli other than STEC include fluoroquinolones (such as ciprofloxacin), macrolides (such as azithromycin), and rifaximin.

Clinicians treating a patient whose clinical syndrome suggests STEC infection (see a clinical syndrome table) should be aware that administering antimicrobial agents may increase the risk of hemolytic uremic syndrome.

Resistance to antimicrobials is increasing worldwide. The decision to use an antibiotic should be carefully weighed against the severity of illness, the possibility that the pathogen is resistant, and the risk of adverse reactions, such as rash, antibiotic-associated colitis, and vaginal yeast infection.

Antimotility agents

Antimotility agents should be avoided for patients with bloody diarrhea; treatment should be reassessed if symptoms have not improved in 48 hours. Antimotility agents also should not be given to patients with STEC infection because these agents may increase the risk of complications, including toxic megacolon, HUS, and neurologic complications.

No known data show that kaolin-pectin compounds (e.g., Kaopectate^®) or lactobacillus slow diarrhea or relieve abdominal cramping.

Hemolytic uremic syndrome (HUS)

HUS, which can be a complication of STEC infection, is a type of thrombotic microangiopathy, characterized by anemia, kidney injury, and a low platelet count (thrombocytopenia).

HUS can lead to permanent health problems and even death.

The features of HUS, especially in adults, can be similar to thrombotic thrombocytopenic purpura (TTP), in which blood clots form in small blood vessels throughout the body. TTP can lead to strokes, brain damage, and death.

HUS diagnosis

HUS is diagnosed using standard blood chemistry and blood count tests.

HUS treatment

HUS is treated with supportive care, including the management of fluids and electrolytes. In some cases, treatment may involve:

• Dialysis
• Transfusions of red blood cells, platelets, or both

With good supportive care, most people with HUS recover completely. Outcomes are typically better for children than adults.