Which blood and urine tests are used in the diagnosis of enterococcal infections?

Updated: Jun 10, 2021
  • Author: Susan L Fraser, MD; Chief Editor: John L Brusch, MD, FACP  more...
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Blood isolates of enterococci should be tested for susceptibility. Routine testing should include penicillin or ampicillin, vancomycin, and high-level aminoglycosides. The Clinical and Laboratory Standards Institute (CLSI), formerly the National Committee for Laboratory Standards (NCCLS), recommends screening enterococci for high-level resistance to both gentamicin and streptomycin.

Urine isolates should be tested for susceptibility to ampicillin and nitrofurantoin. If resistence to both antibiotics is present, testing for susceptibility to fluoroquinolones, doxycycline, linezolid and fosfomycin can be considered.

For VRE isolates associated with infection, susceptibility testing should include a formal MIC determination for ampicillin and an assessment of beta-lactamase production in selected isolates. In addition, susceptibility testing should be requested for linezolid and may be considered for daptomycin, tigecycline, and quinupristin-dalfopristin, plus others as available, although not all of these antibiotics are FDA-approved for VRE infections. CLSI interpretive criteria are not available for non–FDA-approved indications or for certain organisms, so results must be interpreted using expert microbiological and clinical infectious-disease advice.

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