What organisms is daptomycin effective against?

Daptomycin's Antimicrobial Spectrum

Daptomycin is effective against a wide range of Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis and Enterococcus faecium, and streptococci. 1, 2

Specific Organisms Susceptible to Daptomycin

FDA-Approved Indications

Daptomycin is FDA-approved for infections caused by the following organisms:

• Staphylococcus aureus (including methicillin-susceptible and methicillin-resistant isolates) 1
• Streptococcus pyogenes 1
• Streptococcus agalactiae 1
• Streptococcus dysgalactiae subsp. equisimilis 1
• Enterococcus faecalis (vancomycin-susceptible isolates only) for complicated skin and skin structure infections 1

Additional Susceptible Organisms

Clinical evidence and in vitro studies show daptomycin is also effective against:

• Vancomycin-resistant Enterococcus faecium and Enterococcus faecalis (VRE) 2, 3
• Methicillin-resistant Staphylococcus species (MRSS) 3
• Penicillin-resistant Streptococcus pneumoniae (PRSP) 3

Mechanism of Action and Spectrum

Daptomycin is a cyclic lipopeptide antibiotic with a unique mechanism of action:

• It disrupts multiple aspects of bacterial cell membrane function 4
• It inhibits protein, DNA, and RNA synthesis 4
• It provides rapid, concentration-dependent bactericidal activity 2
• It has no cross-resistance with other antibiotic classes 2

Clinical Applications

Daptomycin is particularly valuable for treating:

• Complicated skin and skin structure infections (cSSSI) caused by susceptible Gram-positive bacteria 1, 5
• Staphylococcus aureus bloodstream infections (bacteremia) including right-sided infective endocarditis 1, 5
• Infections caused by multi-drug resistant organisms where other antibiotics may be ineffective 4

Important Limitations

• Not indicated for pneumonia due to inactivation by pulmonary surfactant 1, 6
• Not indicated for left-sided infective endocarditis due to S. aureus (poor outcomes in clinical trials) 1
• Not studied in patients with prosthetic valve endocarditis 1
• Not recommended in children younger than 1 year due to potential effects on muscular, neuromuscular, and nervous systems 1

Dosing Considerations

• For adults: 4-6 mg/kg once daily for cSSSI; higher doses (8-10 mg/kg) may be considered for complicated infections including bacteremia 6
• For pediatric patients (1-17 years): administered by infusion over 30 minutes 1
• Efficacy is calcium-dependent; proper calcium concentrations are essential for optimal activity 3

Resistance Concerns

• Resistance to daptomycin is still uncommon but increasing reports exist, particularly in:
  • Staphylococcus aureus 4
  • Enterococcus faecium 4
  • Enterococcus faecalis 4
• Risk factors for resistance development include prolonged treatment courses, high bacterial burden infections, and inadequate dosing 4

Daptomycin remains a valuable antibiotic option for serious Gram-positive infections, particularly those caused by resistant organisms where traditional therapies may be ineffective.