What bacteria is linezolid (oxazolidinone) effective against?

Linezolid Antimicrobial Coverage

Linezolid is effective against a broad spectrum of gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and penicillin-resistant Streptococcus pneumoniae, making it a valuable option for treating serious gram-positive infections. 1

Gram-Positive Coverage

Staphylococci

• Staphylococcus aureus (including methicillin-resistant strains)
• Staphylococcus epidermidis (including methicillin-resistant strains)
• Staphylococcus haemolyticus

Enterococci

• Enterococcus faecium (including vancomycin-resistant strains)
• Enterococcus faecalis (including vancomycin-resistant strains)

Streptococci

• Streptococcus pneumoniae (including multi-drug resistant isolates)
• Streptococcus pyogenes (Group A streptococci)
• Streptococcus agalactiae (Group B streptococci)
• Viridans group streptococci

Limited Gram-Negative Coverage

• Pasteurella multocida

Anaerobic Coverage

• Clostridium perfringens
• Clostridium difficile
• Peptostreptococcus species
• Bacteroides fragilis

Clinical Applications

Linezolid is particularly valuable for treating infections caused by resistant gram-positive pathogens:

1. MRSA infections: Linezolid is recommended as an oral option for MRSA skin and soft-tissue infections with a strong recommendation (1A) 2

2. Vancomycin-resistant enterococci: Linezolid is considered the drug of choice for infections caused by vancomycin-resistant enterococci 2

3. Multi-drug resistant Streptococcus pneumoniae: Effective against pneumococcal strains resistant to multiple antibiotics 1

Mechanism of Action

Linezolid works through a unique mechanism that differs from other antibiotics:

• Binds to the bacterial 23S ribosomal RNA of the 50S subunit
• Prevents formation of functional 70S initiation complex
• Inhibits bacterial protein synthesis
• Generally bacteriostatic against staphylococci and enterococci
• Bactericidal against streptococci 1

Important Clinical Considerations

1. Resistance concerns: Resistance to linezolid can develop, particularly in Enterococcus faecium with prolonged use or in patients with unremoved prosthetic devices or undrained abscesses 1

2. Adverse effects: Long-term use is limited by:

   • Myelosuppression (thrombocytopenia most common)
   • Peripheral and optic neuropathy (potentially irreversible)
   • Lactic acidosis
   • Serotonin syndrome (when used with serotonergic medications) 2

3. Monoamine oxidase inhibition: Linezolid is a reversible, nonselective inhibitor of monoamine oxidase, which can lead to interactions with adrenergic and serotonergic agents 1

Dosing Considerations

• Standard dose: 600 mg twice daily for most infections
• For uncomplicated skin infections: 400 mg twice daily
• No dosage adjustment needed for mild to moderate renal or hepatic impairment 2

Linezolid's excellent oral bioavailability allows for easy transition from intravenous to oral therapy, making it valuable for outpatient management of serious gram-positive infections that would otherwise require prolonged intravenous therapy.