MRSA Infection Treatment Guidelines

Mechanism of Resistance and Appropriate Antibiotics

MRSA strains are uniformly resistant to cefazolin due to the acquisition of the mecA gene, which encodes a penicillin-binding protein (PBP2a) with significantly lower affinity for beta-lactams, including cefazolin 1
For outpatient MRSA skin and soft tissue infections, the Infectious Diseases Society of America recommends oral options including linezolid, trimethoprim-sulfamethoxazole (TMP-SMX), and tetracyclines (doxycycline or minocycline) 1, 2
For inpatient/severe MRSA infections, the Infectious Diseases Society of America recommends intravenous options including vancomycin as first-line therapy, daptomycin, linezolid, ceftaroline, dalbavancin, telavancin, and tigecycline 1, 2, 3

Cefazolin is effective against methicillin-susceptible S. aureus (MSSA) and is often a preferred agent for MSSA infections, as recommended by the Infectious Diseases Society of America 3, 4
For purulent skin and soft tissue infections likely due to S. aureus (when methicillin-susceptibility is known or highly likely), cefazolin is an appropriate choice, according to the European Society of Clinical Microbiology and Infectious Diseases 5

When empiric coverage for both MSSA and MRSA is needed before culture results are available, appropriate options include vancomycin, daptomycin, or linezolid, not cefazolin, as recommended by the Infectious Diseases Society of America 2, 3
Once MRSA is identified, therapy should be promptly switched to an appropriate anti-MRSA agent, according to the Infectious Diseases Society of America 2, 3