Management of MRSA Infections

Rationale for Ineffectiveness Against MRSA

The Infectious Diseases Society of America (IDSA) guidelines clearly separate treatment recommendations for methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA infections, with cephalexin only appearing in the MSSA treatment category 2
Cephalexin is not effective for treating MRSA infections and should not be used as monotherapy when MRSA is suspected or confirmed, as stated by the Clinical Infectious Diseases guidelines 1, 2

For suspected or confirmed MRSA skin and soft tissue infections (SSTIs), the IDSA recommends trimethoprim-sulfamethoxazole (1-2 double-strength tablets twice daily) as an oral option 2, 3
The IDSA also recommends clindamycin (300-450 mg four times daily) as an oral option for MRSA SSTIs 2, 3
Vancomycin (15-20 mg/kg/day in 2 divided doses) is the parenteral drug of choice for severe MRSA infections, according to the IDSA guidelines 2, 3

Incision and drainage is the primary treatment for purulent skin infections (abscesses) and may be sufficient for uncomplicated cases without systemic symptoms, as recommended by the IDSA 1, 4
Antibiotic therapy active against MRSA is recommended for patients with systemic inflammatory response syndrome (SIRS), failed initial antibiotic treatment, markedly impaired host defenses, or severe or rapidly progressing infections, according to the IDSA guidelines 1, 2

The IDSA warns against the misdiagnosis pitfall of assuming all staphylococcal infections are methicillin-susceptible without obtaining cultures 3
Failing to reassess patients who don't improve within 48-72 hours of starting treatment is a follow-up pitfall to avoid, as recommended by the IDSA 2

Obtaining cultures when possible before starting antibiotics is recommended by the IDSA 4
For purulent infections (abscesses), performing incision and drainage and adding anti-MRSA antibiotic if moderate/severe or with systemic symptoms is recommended by the IDSA 1, 3, 4
Reassessing in 48-72 hours and adjusting therapy based on culture results and clinical response is crucial, as stated by the IDSA 2