Does Meropenem Cover MRSA?
No, meropenem does not have clinically useful activity against MRSA and should never be used as monotherapy for suspected or confirmed MRSA infections.
Microbiological Evidence
The FDA drug label explicitly states that "meropenem does not have in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA)" 1. This is a fundamental limitation of all carbapenems, as they lack activity against methicillin-resistant staphylococci despite their broad-spectrum coverage 2, 3.
Clinical Guideline Recommendations
When MRSA coverage is needed, guidelines consistently recommend adding specific anti-MRSA agents:
For community-acquired pneumonia with MRSA risk factors: Vancomycin (15 mg/kg every 12 hours) or linezolid (600 mg every 12 hours) must be added to any empiric regimen 4
For hospital-acquired pneumonia with MRSA risk factors: Vancomycin or linezolid should be added to the antipseudomonal beta-lactam (which may include meropenem) 4
For proven MSSA infections: Meropenem is inferior to targeted agents like nafcillin, oxacillin, or cefazolin, and de-escalation to these agents is recommended 5
Mechanism of Resistance
MRSA resistance occurs through altered penicillin-binding proteins (specifically PBP2a), which have reduced affinity for all beta-lactams including carbapenems 1. While some research suggests potential synergy when carbapenems are combined with vancomycin or teicoplanin against MRSA 6, 7, this does not translate to meropenem having standalone activity—it remains uniformly resistant 3.
Critical Clinical Pitfall
Never rely on meropenem alone when MRSA is suspected or confirmed. If you are using meropenem for polymicrobial coverage (e.g., Pseudomonas plus gram-negatives) and MRSA is a concern, you must add vancomycin or linezolid as separate anti-MRSA therapy 4. The broad-spectrum nature of carbapenems does not extend to methicillin-resistant organisms 2.