Which gram-positive organisms is meropenem effective against?

Meropenem Coverage of Gram-Positive Organisms

Meropenem is effective against most gram-positive organisms including methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae (penicillin-susceptible isolates), Streptococcus pyogenes, Streptococcus agalactiae, viridans group streptococci, and vancomycin-susceptible Enterococcus faecalis, but lacks activity against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). 1

Specific Gram-Positive Coverage

Meropenem demonstrates activity against the following gram-positive bacteria:

• Staphylococci:

  • Methicillin-susceptible Staphylococcus aureus (MSSA) 1
  • Does NOT cover methicillin-resistant Staphylococcus aureus (MRSA) 1
  • Does NOT cover methicillin-resistant Staphylococcus epidermidis (MRSE) 1

• Streptococci:

  • Streptococcus pneumoniae (penicillin-susceptible isolates only) 1
  • Streptococcus pyogenes (Group A streptococci) 1
  • Streptococcus agalactiae (Group B streptococci) 1, 2
  • Viridans group streptococci 1

• Enterococci:

  • Enterococcus faecalis (vancomycin-susceptible isolates only) 1

• Anaerobic Gram-Positive Bacteria:

  • Peptostreptococcus species 1
  • Clostridium perfringens 1
  • Clostridium difficile 1
  • Propionibacterium acnes 1
  • Eggerthella lenta 1

Clinical Implications

Meropenem's gram-positive coverage makes it suitable for:

1. Mixed infections: Particularly useful in intra-abdominal infections where both gram-positive and gram-negative coverage is needed 3

2. Empiric therapy: Appropriate for serious infections before culture results are available 3

3. Meningitis: Meropenem is the only carbapenem approved for bacterial meningitis due to its low seizure risk compared to imipenem 4, 5

Important Limitations

• MRSA/MRSE: Meropenem does not have activity against methicillin-resistant staphylococci 1
• For suspected MRSA infections, additional coverage with agents like vancomycin would be necessary 3
• For serious infections with suspected resistant gram-positive organisms, combination therapy may be required 6

Synergistic Effects

When combined with other antibiotics, meropenem can show:

• Synergistic effects against some staphylococci when combined with glycopeptides like teicoplanin or vancomycin 6
• Synergistic or additive effects when combined with rifampicin, co-trimoxazole, or ciprofloxacin against staphylococcal species 6

Meropenem's broad spectrum of activity against both gram-positive and gram-negative organisms makes it a valuable option for empiric therapy in serious infections, though its use should be judicious to prevent development of resistance.