Vancomycin-resistant enterococci laboratory findings

Vancomycin-resistant enterococci Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Vancomycin-Resistant Enterococci from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Laboratory Findings
X Ray
CT
MRI
Echocardiography or Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Vancomycin-resistant enterococci laboratory findings On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Vancomycin-resistant enterococci laboratory findings All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA onVancomycin-resistant enterococci laboratory findings
CDC on Vancomycin-resistant enterococci laboratory findings
enterococci laboratory findings in the news
on Vancomycin-resistant enterococci laboratory findings
Directions to Hospitals Treating Vancomycin-resistant enterococci
Risk calculators and risk factors for Vancomycin-resistant enterococci laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Please help WikiDoc by adding more content here. It's easy! Click here to learn about editing.

Laboratory Findings

Susceptibility Testing

E. faecium is the most frequently isolated species of VRE in hospitals and typically produces high vancomycin (>128 µg/ml) and teicoplanin (>16 µg/ml) minimum inhibitory concentrations (MICs). These isolates typically contain vanA genes. A vanB-containing isolate typically produces lower level resistance to vancomycin (MICs 16 to 64 µg/ml) and is susceptible to teicoplanin (MICs <1 µg/ml). Recently, a few vanD--containing isolates of E. faecium with a moderate level of resistance to vancomycin (MICs 64 to 128 µg/ml) and teicoplanin (MICs 4-8 µg/ml) have been reported, as has a novel vanE-containing E. faecalis. E. gallinarum and E. casseliflavus/E. flavescens isolates are intrinsically resistant to vancomycin. These isolates contain vanC genes that typically produce vancomycin MICs of 2 to 16 µg/ml.

Species Differentiation

Identification of VRE to species level aids in confirming whether an isolate has intrinsic (vanC) or acquired resistance (vanA or vanB). Knowledge of the type of resistance is critical for infection control purposes. vanA and vanB genes are transferable and can spread from organism to organism. In contrast, vanC genes are not transferable, have been associated less commonly with serious infections, and have not been associated with outbreaks.

For species differentiation, motility and pigment tests are easily performed and are important tests to distinguish among species phenotypically. E. faecium and E. faecalis are non-motile, whereas E. gallinarum and E. casseliflavus/E. flavescens generally are motile. Most isolates of E. casseliflavus/E. flavescens have a distinct yellow pigment, which can be observed by collecting growth from an agar plate on a swab. In addition to motility and pigment tests, an organism's susceptibility profile also helps differentiate vanA and vanB isolates from vanC isolates.