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Cocos Gram-positivos

Enterococcus faecium

Gram-positive cocci in short chains

Identification & Growth

Identification

  • Catalase-negative, PYR-positive, bile-esculin-positive
  • Arabinose-positive

Growth Conditions

  • Blood agar and bile-esculin agar, 35 °C, 24–48 h

Clinical Significance

  • ICU bacteremia, surgical-site infection, intestinal colonization

Intrinsic Resistance

  • Cephalosporins, low-level aminoglycosides, SXT, clindamycin, aztreonam, polymyxins (EUCAST Expected Resistant Phenotypes v1.2)

Bench Alerts

  • Ampicillin resistance is the rule (commonly >80% in hospital isolates), unlike E. faecalis
  • VRE: screen with vancomycin; confirm by MIC and notify infection control immediately

Clinical Notes

Clinical presentations

  • Causes nosocomial bacteremia, particularly in immunosuppressed, oncology, and intensive care patients.
  • Associated with intra-abdominal and urinary tract infections in patients with extensive prior hospital exposure.
  • A relevant cause of endocarditis in the context of structural heart disease and prosthetic devices.

Specimens and collection

  • Blood cultures should be drawn before any empiric antimicrobial change in inpatients with VRE risk factors.
  • Rectal swab is the standard active surveillance method for vancomycin-resistant Enterococcus colonization.

Epidemiology and at-risk populations

  • It is the predominant species among vancomycin-resistant Enterococcus isolates in the hospital setting.
  • Patients with prolonged hospitalization, extensive broad-spectrum antimicrobial use, and transplant recipients have elevated risk of VRE colonization/infection.
  • Nosocomial transmission occurs via direct contact and contaminated surfaces, requiring contact precautions.

Resistance and therapeutic implications

  • Most clinical isolates are ampicillin-resistant, unlike E. faecalis, severely restricting therapeutic options.
  • Vancomycin resistance (vanA/vanB genes) is frequent and requires laboratory confirmation and use of alternative agents such as linezolid or daptomycin.
  • Exhibits intrinsic cephalosporin resistance and intrinsic low-level aminoglycoside resistance, requiring high-level testing to assess synergy.

Bench and reporting notes

  • Growth on bile-esculin and in 6.5% NaCl, catalase-negative, guides genus identification before species differentiation.
  • Confirmation of vancomycin resistance should be reported immediately to the hospital infection control committee.
  • The report should highlight intrinsic cephalosporin resistance and flag the high prevalence of ampicillin resistance in this species.

Sources

Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.

FAQ: Frequently Asked Questions

How to identify Enterococcus faecium in the lab?

Enterococcus faecium is identified through catalase-negative, pyr-positive, bile-esculin-positive, arabinose-positive.

What are the intrinsic resistances of Enterococcus faecium?

This organism is naturally resistant to cephalosporins, low-level aminoglycosides, sxt, clindamycin, aztreonam, polymyxins (eucast expected resistant phenotypes v1.2). These drugs should not be reported as susceptible.

Where is Enterococcus faecium commonly found?

It is typically associated with icu bacteremia, surgical-site infection, intestinal colonization.

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