Test Summary
Shiga Toxins, EIA With Reflex to E coli O157, Culture
Test code: 30264
Clinical use
- Diagnose Shiga toxin–producing Escherichia coli (STEC) infection
Clinical background
Escherichia coli Shiga toxins are in the same toxin family as that produced by Shigella dysenteriae type 1.1 The main types of Shiga toxins produced by E coli are ST-I and ST-II. The bacteria that produce these toxins are transmitted to humans via E coli-contaminated food (undercooked meat or raw milk, vegetables, or fruit) and water, as well as by person-to-person and animal contact.2
STEC infection may lead to asymptomatic infection or mild to severe hemorrhagic colitis characterized by abdominal pain and watery or bloody diarrhea.3 Up to 10% of patients with STEC infection may progress to hemolytic uremic syndrome (HUS), a life-threatening complication that includes acute renal failure, hemolytic anemia, and thrombocytopenia.4 Children and the elderly are the most vulnerable to HUS and should receive aggressive care during STEC infection.5 Early diagnosis of STEC infection is important to help decrease renal damage and prevent inappropriate antibiotic therapy or unnecessary invasive diagnostic procedures (eg, appendectomy for severe abdominal pain).1 Early diagnosis of STEC infection also helps limit further spread of the pathogen via prompt public health response.
The Centers for Disease Control and Prevention recommends that stool samples from all patients with acute, community-acquired diarrhea or possible HUS be tested for Shiga toxins and cultured for E coli O157.1,6 E coli O157:H7 causes an estimated 36% of STEC infections each year in the United States, making it the most common individual strain to cause disease.1,6 O157 infections are more likely to cause severe disease outcomes than non-O157 strains.3,7 However, some non-O157 strains can cause comparably severe STEC infections.8,9 Traditional culture methods using selective media identify only O157 STEC, leading to delayed or missed diagnosis of non-O157 STEC infection.1,6
The Quest Diagnostics Shiga Toxins, EIA With Reflex to E coli O157 Culture test begins with an enzyme immunoassay (EIA) that detects Shiga toxins from both O157 and non-O157 STEC strains. Quest performs E coli O157 Culture, at an additional charge (CPT code 87046), on all samples that are positive for Shiga toxin.
Individuals suitable for testing
- Individuals with acute community-acquired diarrhea1,6
- Individuals with diarrhea accompanied by bloody or mucoid stools, fever, severe abdominal cramping, or signs of sepsis2
- Individuals with chronic diarrhea who have no alternative diagnosis established1,6
- Individuals with suspected HUS1,6
Method
- EIA detecting both ST-I and ST-II
- Utilizes monoclonal ST-I and ST-II capture antibodies and enzyme-conjugated polyclonal Shiga toxin antibodies for toxin detection
- Clinical sensitivity: 100%10
- Clinical specificity: 99.9%10
Interpretive information
A positive result (toxin detected) on the EIA indicates the presence of Shiga toxin produced by E coli or Shigella dysenteriae type 1. All positive results are reflexed to E coli O157 Culture. For specimens with reflex E coli O157 culture, a positive result indicates the presence of E coli O157. A negative result indicates infection with an agent other than E coli O157.
A not-detected toxin result indicates the absence of Shiga toxin or a level of toxin below the limit of detection of the assay. Neither a positive nor a negative result precludes the presence of other infectious agents.
References
- Gould LH, Bopp C, Strockbine N, et al. Recommendations for diagnosis of Shiga toxin-producing Escherichia coli infections by clinical laboratories. MMWR Recomm Rep. 2009;58(RR-12):1-14.
- Shane AL, Mody RK, Crump JA, et al. 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea. Clin Infect Dis. 2017;65(12):1963-1973. doi:10.1093/cid/cix959
- Cleary TG. The role of Shiga-toxin-producing Escherichia coli in hemorrhagic colitis and hemolytic uremic syndrome. Semin Pediatr Infect Dis. 2004;15(4):260-265. doi:10.1053/j.spid.2004.07.007
- World Health Organization. E. coli fact sheet. Updated February 7, 2018. Accessed January 9, 2025. https://www.who.int/news-room/fact-sheets/detail/e-coli
- Gould LH, Demma L, Jones TF, et al. Hemolytic uremic syndrome and death in persons with Escherichia coli O157:H7 infection, Foodborne Diseases Active Surveillance Network sites, 2000-2006. Clin Infect Dis. 2009;49(10):1480-1485. doi:10.1086/644621
- Gould LH. Update: recommendations for diagnosis of Shiga toxin-producing Escherichia coli infections by clinical laboratories. Clinical Microbiology Newsletter. 2012;34(10):75-83. doi:10.1016/j.clinmicnews.2012.04.004
- Hadler JL, Clogher P, Hurd S, et al. Ten-year trends and risk factors for non-O157 Shiga toxin-producing Escherichia coli found through Shiga toxin testing, Connecticut, 2000-2009. Clin Infect Dis. 2011;53(3):269-276. doi:10.1093/cid/cir377
- Hermos CR, Janineh M, Han LL, et al. Shiga toxin-producing Escherichia coli in children: diagnosis and clinical manifestations of O157:H7 and non-O157:H7 infection. J Clin Microbiol. 2011;49(3):955-959. doi:10.1128/jcm.02119-10
- Johnson KE, Thorpe CM, Sears CL. The emerging clinical importance of non-O157 Shiga toxin-producing Escherichia coli. Clin Infect Dis. 2006;43(12):1587-1595. doi:10.1086/509573
- SHIGA TOXIN CHEK™. Package insert. TECHLAB®, Inc.; 2021. Accessed January 9, 2025. https://www.techlab.com/wp-content/uploads/2021/09/SHIGA-TOXIN-CHEK-PI-91-696-01-TL_7-2021.pdf
Content reviewed 01/2025
30264 - Shiga Toxins, EIA with Reflex to E. coli O157, Culture
Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.
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