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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 Enterococcus 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.
Identifying carriers of vancomycin-resistant enterococci
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.
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