Does Augmentin Cover MRSA?
No, Augmentin (amoxicillin/clavulanate) does not provide reliable coverage for MRSA and should not be used to treat MRSA infections. MRSA produces an altered penicillin-binding protein (PBP2a) encoded by the mecA gene that confers resistance to all commercially available beta-lactam antibiotics, including Augmentin 1.
Why Augmentin Fails Against MRSA
MRSA is resistant to all beta-lactams: The mecA gene produces PBP2a, which has reduced affinity for all beta-lactam antibiotics, rendering the entire class ineffective regardless of beta-lactamase inhibition 1.
Clavulanate cannot overcome mecA-mediated resistance: While clavulanic acid effectively inhibits staphylococcal beta-lactamases and restores activity against methicillin-susceptible S. aureus (MSSA) producing penicillinase, it has no effect on the altered PBP2a that causes MRSA resistance 2, 3.
Historical context matters: Older studies from the 1980s showing Augmentin activity against "resistant staphylococci" were referring to penicillinase-producing MSSA, not MRSA 4, 5. This distinction is critical—these are fundamentally different resistance mechanisms.
Appropriate Treatment for MRSA
Outpatient/Oral Options
- Trimethoprim-sulfamethoxazole (1-2 double-strength tablets twice daily) is the preferred first-line oral agent 6, 7.
- Clindamycin (300-450 mg three times daily) provides coverage for both MRSA and beta-hemolytic streptococci 6.
- Doxycycline (100 mg twice daily) or minocycline (200 mg loading, then 100 mg twice daily) are effective alternatives 6.
- Linezolid (600 mg twice daily) is highly effective but more expensive 6.
Inpatient/IV Options
- Vancomycin (15-20 mg/kg every 8-12 hours) remains the first-line parenteral option 6, 7.
- Linezolid (600 mg IV/PO twice daily) shows excellent efficacy for complicated infections 6.
- Daptomycin (4 mg/kg daily) is effective for complicated skin infections 6.
Treatment Duration and Key Principles
- 5-10 days for uncomplicated skin infections 6.
- 7-14 days for complicated infections 6.
- Incision and drainage is the mainstay of therapy for abscesses and should be performed whenever feasible 6.
- Obtain cultures before starting antibiotics to confirm MRSA and guide therapy 6.
Common Pitfall
The most critical error is assuming that adding a beta-lactamase inhibitor (clavulanate) can overcome MRSA resistance. This fundamentally misunderstands the mecA-mediated resistance mechanism, which affects the target site (PBP2a) rather than involving beta-lactamase production 1, 2.