Is vancomycin effective against Streptococcus (Strep) and Staphylococcus (Staph) species?

Vancomycin Coverage for Streptococcus and Staphylococcus Species

Vancomycin is highly effective against both Streptococcus and Staphylococcus species, including methicillin-resistant Staphylococcus aureus (MRSA), making it an important antibiotic for serious gram-positive infections. 1

Antimicrobial Spectrum of Vancomycin

Vancomycin demonstrates excellent activity against:

• Staphylococcus species:

  • Staphylococcus aureus (including methicillin-resistant strains)
  • Staphylococcus epidermidis (including methicillin-resistant strains)
  • Other coagulase-negative staphylococci 1, 2

• Streptococcus species:

  • Streptococcus pneumoniae (including penicillin-resistant strains)
  • Streptococcus pyogenes (Group A strep)
  • Streptococcus agalactiae (Group B strep)
  • Streptococcus bovis
  • Viridans group streptococci 1, 3

Mechanism of Action

Vancomycin works through a unique mechanism:

• Inhibits the second stage of cell wall synthesis in susceptible bacteria
• Binds to the D-alanyl-D-alanine terminus of cell wall precursor units
• Alters bacterial cell membrane permeability
• Selectively inhibits RNA synthesis 2, 3

This mechanism makes vancomycin bactericidal against most susceptible organisms, particularly staphylococci and streptococci.

Clinical Applications

Vancomycin is indicated for:

1. Serious staphylococcal infections when:

   • Patients are intolerant to beta-lactams (penicillins/cephalosporins)
   • The organism is resistant to commonly used agents (MRSA) 4

2. Streptococcal infections including:

   • Streptococcal endocarditis in penicillin-intolerant patients
   • Serious streptococcal infections 5

3. Skin and soft tissue infections with suspected or confirmed MRSA involvement 4, 6

4. Necrotizing fasciitis when group A streptococcal or MRSA etiology is suspected 4

Dosing Considerations

For serious infections:

• Adults: 15-20 mg/kg IV every 8-12 hours (not to exceed 2g per dose)
• Children: 15 mg/kg IV every 6 hours 4

For optimal efficacy against serious infections:

• Target trough concentrations of 15-20 μg/mL for bacteremia, endocarditis, osteomyelitis, meningitis, and severe SSTI 4
• AUC/MIC ratio >400 is the pharmacodynamic parameter best predicting efficacy 4

Synergistic Combinations

Vancomycin demonstrates synergy when combined with:

• Aminoglycosides against Staphylococcus aureus, Streptococcus bovis, enterococci, and viridans group streptococci 1, 3
• This synergy can be particularly useful in serious, deep-seated infections 3

Limitations and Considerations

1. Resistance concerns:

   • "Vancomycin creep" phenomenon with slowly increasing MICs in some regions 7
   • Strains with MICs of 1.5-2 μg/mL associated with higher treatment failure rates 7

2. Adverse effects:

   • Nephrotoxicity, especially with higher trough levels or prolonged therapy
   • "Red man syndrome" (histamine-related infusion reaction)
   • Ototoxicity (less common with modern formulations) 8, 7

3. Alternative agents when vancomycin is not appropriate:

   • Daptomycin (for MRSA bacteremia)
   • Linezolid (for MRSA pneumonia)
   • Clindamycin (for susceptible community-acquired MRSA) 4, 6

Conclusion

Vancomycin remains a cornerstone antibiotic for serious gram-positive infections, with reliable activity against both streptococci and staphylococci, including resistant strains. Its appropriate use should be guided by local resistance patterns, patient-specific factors, and the site/severity of infection.