Will linezolid be effective in treating a patient with Enterococcus faecium infection who is susceptible to Gentamycin, tetracycline, and vancomycin?

Linezolid Coverage for Enterococcus faecium

Yes, linezolid will effectively cover this Enterococcus faecium infection, with 97-99% susceptibility rates against E. faecium strains including multidrug-resistant isolates. 1, 2

Treatment Recommendation

Linezolid 600 mg IV or orally every 12 hours is the appropriate treatment choice for this patient. 1

Why Linezolid is Appropriate Here

• Linezolid demonstrates excellent activity against E. faecium with susceptibility rates of 97-99%, even against multidrug-resistant strains 1, 2
• The FDA has approved linezolid for treatment of vancomycin-resistant E. faecium infections, and it remains highly effective against vancomycin-susceptible strains as well 2
• Linezolid is bacteriostatic against enterococci, which is adequate for most clinical scenarios 3, 2

Clinical Context Matters

The fact that your patient's isolate is susceptible to gentamicin, tetracycline, and vancomycin indicates this is not a multidrug-resistant strain. However, this doesn't change linezolid's appropriateness:

• For vancomycin-susceptible, ampicillin-resistant E. faecium, vancomycin remains first-line therapy 1
• Linezolid serves as an excellent alternative when vancomycin cannot be used (allergy, renal dysfunction, or clinical failure) 1
• If the isolate is ampicillin-susceptible (not mentioned in your susceptibility panel), ampicillin would be preferred over all other options 1

Treatment Duration by Infection Site

• Uncomplicated infections: 7-14 days 1
• Complicated infections or bacteremia: 10-14 days 1
• Endocarditis: At least 6 weeks 3, 1

Critical Monitoring Requirements

Watch for these linezolid-specific toxicities, especially with prolonged use (>14-21 days): 3, 1, 4

• Bone marrow suppression (thrombocytopenia most common) - monitor CBC weekly
• Peripheral and optic neuropathy - assess for visual changes and paresthesias
• Serotonin syndrome - avoid concurrent serotonergic agents 2

Important Caveats

• Resistance can emerge during therapy: In clinical trials, linezolid resistance developed in 6 patients with E. faecium, particularly in those with unremoved prosthetic devices or undrained abscesses 2, 5
• Resistance is reversible: One case report documented E. faecium reverting to linezolid susceptibility after discontinuation, then becoming resistant again upon re-treatment 5
• Nosocomial transmission of linezolid-resistant strains has been documented 6

When to Consider Alternatives

If the patient has severe/invasive infection requiring bactericidal activity:

• Daptomycin 10-12 mg/kg/day IV is preferred for bactericidal effect 1, 7
• Consider combination therapy with daptomycin plus ampicillin or ceftaroline for synergistic activity 3, 1

If the patient cannot tolerate linezolid:

• Daptomycin monotherapy at high doses (10-12 mg/kg/day) 1
• For E. faecium only (not E. faecalis): quinupristin-dalfopristin, though rarely used due to severe side effects 1, 4