Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

Clinical References: Homburger HA: Allergic diseases. In Clinical Diagnosis and Management by
Laboratory Methods. 21st edition. Edited by RA McPherson, MR Pincus. New York, WB Saunders
Company, 2007, Chapter 53, Part VI, pp 961-971
800071 Shiga Toxin Escherichia coli Antigen, Feces
Clinical Information: Shiga toxin-producing Escherichia coli (STEC) have been recognized as
agents of diarrhea and of sporadic cases and serious outbreaks of life-threatening hemorrhagic colitis and
hemolytic uremic syndrome (HUS). Escherichia coli O157:H7 is the most frequently isolated
enterohemorrhagic Escherichia coli (EHEC) serotype, but at least 50 serotypes have been implicated in
the production of cytotoxins and development of complications. Conventional testing methods for
Escherichia coli O157: H7 involve isolation of the organism from fecal cultures followed by biochemical
and immunologic confirmation. This method usually requires 72 hours for complete identification. At this
time, because antimicrobial therapy does not appear to be useful for treating the disease and may even
increase the risk of HUS, recovery of Escherichia coli O157: H7 by culture for antimicrobial
susceptibility testing is not necessary. The rapid diagnosis of Escherichia coli O157:H7 directly from fecal
specimens is preferred to avoid unnecessary diagnostic procedures and inappropriate antimicrobial
therapy and to identify common sources linked to transmission.
STXRP
89565
Useful For: Rapid screening for EHEC serotypes including Escherichia coli O157:H7. This test should
serve as an adjunct to culture. However, in some situations when recovery of the organism by culture is
not optimal (e.g. delayed transport of the specimen or transport of the specimen in preservative), or when
isolation of the organism is not required for epidemiologic studies, this test may be considered as the
preferred diagnostic method.
Interpretation: A positive result suggests the presence of Shiga-like toxin 1 or 2. It is recommended
that all positive specimens be cultured to confirm the presence of enteropathogenic coli. A negative result
does not rule out the presence of enteropathogenic Escherichia coli; detectable antigen levels may not be
produced until 3-6 days after the development of symptoms.
Reference Values:
Negative
Clinical References: 1. Karmali MA: Infection by verocytotoxin-producing Escherichia coli. Clin
Microbiol Rev 1989;2:15-38 2. Karmali MA, Petric M, Lim C, et al: The association between idiopathic
hemolytic uremic syndrome and infection by verotoxin-producing Escherichia coli. J Infect Dis
1985;151:775-782 3. Griffin PM, Ostroff SM, Tauxe RV, et al: Illnesses associated with Escherichia coli
O157:H7 infections. A broad clinical spectrum. Ann Intern Med 1988;109:705-712 4. Wong CS, Jelacic
S, Habeeb RL, et al: The risk of the hemolytic-uremic syndrome after antibiotic treatment of Escherichia
coli O157:H7 infections. N Engl J Med 2000;342:1930-1936
Shiga Toxin, Molecular Detection, PCR, Feces
Clinical Information: Shiga toxins (also known as Shiga-like toxins, Vero toxins, or Vero-like
toxins) are encoded by some strains of Escherichia coli, most notably O157:H7. Shiga toxin can also be
produced by other serogroups of enterohemorrhagic Escherichia coli (EHEC), as well as Shigella
dysenteriae type 1. Generally, Shiga toxin-producing organisms cause bloody diarrhea, although this is
not universal. Unlike some bacterial gastrointestinal infections, antimicrobial therapy is contraindicated,
as antimicrobials may exacerbate disease. Treatment is primarily supportive (eg, hydration). A
complication of infection by an organism producing Shiga toxin is hemolytic uremic syndrome (HUS).
The percentage of people that develop HUS varies among outbreaks of Escherichia coli O157:H7, but
generally ranges from 3% to 20%. HUS is characterized by a triad of findings: hemolytic anemia,
thrombocytopenia, and kidney failure. Most people recover completely, however, some require permanent
dialysis, and some die as a result of complications. Several diagnostic methods available for the detection
of EHEC lack sensitivity, are labor intensive, or have a long turnaround time. There are more than 160
serogroups of EHEC; the first serogroup to be associated with HUS was O157:H7. This is also the
serogroup that is most commonly implicated in outbreaks. EHEC O157:H7 is detectable as nonfermenting
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