What organisms is vancomycin effective against?

Organisms Covered with Vancomycin

Vancomycin is effective against gram-positive cocci and bacilli, including methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), enterococci (particularly Enterococcus faecalis), streptococci (including penicillin-resistant Streptococcus pneumoniae), and Clostridium species, but has no activity against gram-negative bacteria, mycobacteria, or fungi. 1

Primary Gram-Positive Cocci Coverage

Staphylococci

• Staphylococcus aureus (including methicillin-resistant strains - MRSA) 1, 2
• Staphylococcus epidermidis (including multiply resistant strains and methicillin-resistant strains - MRSE) 1, 2
• Staphylococcus haemolyticus (though vancomycin-resistant strains have been isolated) 3

Streptococci

• Streptococcus pneumoniae (including penicillin-resistant and multiply resistant strains) 1, 2
• Streptococcus pyogenes (Group A Streptococcus) 1, 2
• Streptococcus agalactiae (Group B Streptococcus) 1, 2
• Streptococcus bovis 1, 2
• Viridans group streptococci (including Streptococcus mutans) 1, 2

Enterococci

• Enterococcus faecalis 1
• Enterococcus faecium (though vancomycin-resistant enterococci - VRE - are increasingly common, particularly with E. faecium) 3

Gram-Positive Bacilli Coverage

• Clostridium species (including Clostridium difficile when used orally for antibiotic-associated colitis) 3, 2
• Listeria monocytogenes 1, 2
• Diphtheroids (Corynebacterium species) 1, 2
• Actinomyces species 1, 2
• Lactobacillus species 1, 2

Critical Coverage Gaps

• No activity against gram-negative bacilli 1
• No activity against mycobacteria 1
• No activity against fungi 1
• Vancomycin-resistant enterococci (VRE) are not covered, particularly Enterococcus faecium strains carrying the vanA gene 3

Synergistic Combinations

• Vancomycin plus aminoglycosides demonstrate synergistic activity against Staphylococcus aureus, Streptococcus bovis, enterococci, and viridans group streptococci 1, 2
• Vancomycin plus rifampin shows enhanced activity against Staphylococcus aureus 2

Important Clinical Considerations

When Vancomycin is Appropriate

• Treatment of serious infections caused by beta-lactam-resistant gram-positive microorganisms 3
• Treatment of gram-positive infections in patients with serious beta-lactam allergies 3
• Empirical coverage for gram-positive cocci in blood cultures pending identification, particularly in critically ill patients or those with suspected MRSA 4

Resistance Concerns

• The "vancomycin creep" phenomenon describes slow upward trending of vancomycin MIC values from <1 mcg/mL to higher values, with strains having MICs of 1.5-2 mcg/mL associated with high therapeutic failure rates 5
• Alternative therapies should be considered when Staphylococcus aureus demonstrates vancomycin MIC ≥2 mg/L, as the target AUC:MIC ratio of ≥400 is unlikely to be achieved 6

Common Pitfalls to Avoid

• Do not use vancomycin for gram-negative infections as it has no activity against these organisms 1
• Do not continue vancomycin unnecessarily when cultures identify organisms susceptible to narrower-spectrum antibiotics, as this promotes vancomycin resistance 4
• Do not assume all enterococci are vancomycin-susceptible, particularly Enterococcus faecium, which frequently demonstrates vancomycin resistance 3