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Test Code VRERP Vancomycin-Resistant Enterococcus, Molecular Detection, PCR

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name


Specimen Type


Necessary Information

Specimen source is required.

Specimen Required

The high sensitivity of amplification by PCR requires the specimen to be processed in an environment in which contamination of the specimen by Vancomycin-Resistant Enterococcus DNA is unlikely.


Submit only 1 of the following specimens:



Culturette (BBL Culture Swab) (T092)

C and S Vial (T058)

Stool container, Small (Random), 4 oz Random (T288)



Specimen Type: Perianal, perirectal, rectal

Container/Tube: Culture transport swab (Dacron or rayon swab with aluminum or plastic shaft with either Stuart or Amies liquid medium [T092])

Specimen Volume: Swab



Specimen Type: Preserved Stool

Container/Tube: Commercially available transport system specific for recovery of enteric pathogens from fecal specimens (15 mL of non-nutritive transport medium containing phenol red as a pH indicator, either Cary-Blair, Para-Pak C and S [T058])

Specimen Volume: Representative portion of stool

Collection Instructions:

1. Collect fresh stool and submit 1 gram or 5 mL in container with transport medium.

2. Place stool in preservative within 2 hours of collection.


Specimen Type: Unpreserved stool

Container/Tube: Stool container (T288)

Specimen Volume: Representative portion of stool

Reject Due To








E-swab, calcium alginate swab, cotton-tipped swab, swab sent in gel transport medium, swab sent in viral or universal transport medium, or dry swab; formalin or PVA fixative


Specimen Stability Information

Specimen Type Temperature Time
Varies Refrigerated (preferred) 7 days
  Ambient  7 days
  Frozen  7 days

Day(s) and Time(s) Performed

Monday through Friday

Specimen Retention Time

3 days if received in a swab transport

Analytic Time

1 day

Reference Values

Not applicable

Useful For

Identifying carriers of vancomycin-resistant enterococci

Method Name

Real-Time Polymerase Chain Reaction (PCR)

Test Classification

This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value


Result ID Test Result Name Result LOINC Value
SRC60 Specimen source 31208-2
84406 VRE PCR 71718-1

Clinical Information

Vancomycin-resistant enterococci (VRE) are major nosocomial pathogens. Patients who are particularly vulnerable to fatal disease from VRE include those with hematologic malignancies and liver transplants. Nosocomial spread of VRE occurs as the result of fecal carriage. Risks for both colonization and infection include prolonged hospitalization, intensive care unit stay, transplantation, hematologic malignancies, and prolonged exposure to antibiotics.


The Centers for Disease Control and Prevention provides recommendations to prevent the spread of VRE in institutional settings. These recommendations include isolation of patients experiencing active VRE infection, screening of patients by perianal swab or fecal testing to identify carriers of VRE, and subsequent isolation or cohorting of VRE carriers. Identification and isolation of VRE carriers has been shown to be cost-effective.


In Enterococcus faecalis or E faecium, vancomycin resistance is usually associated with the presence of the vanA or vanB genes. The presence of these genes is detected by a molecular method in this assay.


Positive test results indicate the presence of either the vanA or vanB gene, which confers vancomycin resistance in Enterococcus faecalis and Enterococcus faecium (and occasionally other organisms). Patients with a positive test result should be placed in isolation or cohorted with other vancomycin-resistant enterococci (VRE) carriers according to the institution's infection control practices.


A negative result indicates the absence of detectable vanA or vanB DNA in the specimen but does not rule-out carrier status as false-negative results may occur due to inhibition of PCR, sequence variability underlying primers or probes, or the presence of VRE in quantities less than the limit of detection of the assay. In the rare event that PCR testing appears to be negative but there is evidence of PCR inhibition, the result will read "PCR inhibition present," in such a case, a new specimen should be submitted for repeat testing.


A positive result does not imply the presence of vancomycin-resistant enterococci (VRE) disease; the presence of vanA or vanB genes correlates with colonization by VRE. Colonization with VRE is not associated with any signs or symptoms.


vanA or vanB genes may occasionally be found in organisms other than enterococci.

Clinical Reference

1. Sloan LM, Uhl JR, Vetter EA, et al: Comparison of the Roche LightCycler vanA/vanB detection assay and culture for detection of vancomycin-resistant enterococci from perianal swabs. J Clin Microbiol 2004;42:2636-2643

2. Mayo Medical Laboratories Communique: Vancomycin-resistant enterococci: Colonization, infection, detection, and treatment. Vol 32, No. 11, November 2007

3. Zirakzadeh A, Patel R: Epidemiology and mechanisms of glycopeptide resistance in enterococci. Curr Opin Infect Dis 2005;18:507-512

4. Zirakzadeh A, Patel R: Vancomycin-resistant enterococci colonization, infection detection and treatment. Mayo Clinic Proc 2006;81:529-536

5. Patel R: Enterococcal-type glycopeptide resistance genes in non-enterococcal organisms. FEMS Microbiol Lett 2000 Apr 1;185(1):1-7

Method Description

Bacterial DNA is extracted from the specimen. Using the LightCycler instrument and fluorescent energy transfer probes, vanA and vanB genes responsible for vancomycin resistance in enterococci are detected directly from perianal swabs or fecal specimens.(Sloan LM, Uhl JR, Vetter EA, et al: Comparison of the Roche LightCycler vanA/vanB detection assay and culture for detection of vancomycin-resistant enterococci from perianal swabs. J Clin Microbiol 2004;42:2636-2643)

Supportive Data

Perianal swabs (894) were evaluated for the presence of vanA or vanB DNA by the vancomycin-resistant enterococci (VRE) PCR assay and compared to culture using selective and differential media. Compared to culture the VRE PCR assay was 98% sensitive and 98% specific. The VRE PCR assay detected 35 more positive specimens than the culture method. No cross-reactivity was seen when tested on a panel of pathogenic and normal flora bacteria of the gastrointestinal tract. Enterococcus species containing the vanC gene were not detected with the VRE PCR assay.


If not ordering electronically, complete, print, and send a Microbiology Test Request Form (T244) with the specimen (