TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: E157C    
Escherichia coli O157:H7 Culture, Feces

Useful For Suggests clinical disorders or settings where the test may be helpful

Determining whether Escherichia coli O157:H7 may be the cause of diarrhea

 

Reflexive testing for Shiga toxin and/or E coli O157:H7 nucleic acid amplification test-positive feces

 

This test is generally not useful for patients hospitalized more than 3 days because the yield from specimens from these patients is very low, as is the likelihood of identifying a pathogen that has not been detected previously.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

When this test is ordered, the reflex tests may be performed and charged separately.

 

See Laboratory Testing for Infectious Causes of Diarrhea in Special Instructions.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Diarrhea may be caused by a number of agents, including bacteria, viruses, parasites, and chemicals; these agents may result in similar symptoms. A thorough patient history covering symptoms, severity and duration of illness, age, travel history, food consumption, history of recent antibiotic use, and illnesses in the family or other contacts will help the healthcare provider determine the appropriate testing to be performed.

 

Shiga toxin-producing Escherichia coli (STEC) are E coli strains capable of producing Shiga toxin, which can result in diarrhea that can be bloody. The incubation period between exposure and symptom onset is 1 to 9 days. Hemolytic-uremic syndrome (HUS) is a systemic complication of STEC infection and is characterized by renal failure, microangiopathic hemolytic anemia, and nonimmune thrombocytopenia. HUS complicates approximately 15% of STEC infections in children younger than 10 years and 6% to 9% overall.

 

Treatment of STEC infection consists of supportive care. Antibiotic therapy is generally not beneficial in patients with STEC infection and has been associated with development of HUS in some studies. Thus, when STEC is clinically suspected, antibiotics should be withheld. Antiperistaltic agents also increase the risk of systemic complications and should be avoided.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

No growth of pathogen

Interpretation Provides information to assist in interpretation of the test results

The growth of Escherichia coli O157:H7 identifies a potential cause of diarrhea.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

The yield of Escherichia coli O157:H7 is reduced when specimens are delayed in transit to the laboratory (>2 hours from collection for unpreserved specimens).

 

Check local public health requirements, which may require submission of isolates to a public health laboratory.

 

Primary testing for Shiga toxin-producing E coli using Shiga toxin PCR and not specifically just for E coli O157:H7 is recommended because roughly half of Shiga toxin-producing E coli are not O157:H7.

 

Susceptibilities should not be performed on E coli O157:H7 since antibiotics are not used for treatment. Any healthcare provider contemplating a request for susceptibility testing on E coli O157:H7 should consult with the Laboratory Section Director for guidance.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Pillai DR: Fecal culture for Campylobacter and related organisms. In Clinical Microbiology Procedures Handbook, Fourth edition. Washington, DC, ASM Press, 2016, Section 3.8.2

2. DuPont HL: Persistent diarrhea: A clinical review. JAMA, 2016;315(24):2712-2723 doi:10.1001/jama.2016.7833

3. Page AV, Liles WC: Enterohemorrhagic Escherichia coli infections and the hemolytic-uremic syndrome. Med Clin North Am 2013;97:681

4. Nelson JM, Griffin PM, Jones TF, et al: Antimicrobial and antimotility agent use in persons with shiga toxin-producing Escherichia coli O157 infection in FoodNet Sites. Clin Infect Dis 2011;52:1130

Special Instructions Library of PDFs including pertinent information and forms related to the test