What are the recommended treatments for infections caused by MRSA (methicillin‑resistant Staphylococcus aureus) and streptococci?

Treatment for MRSA and Streptococcal Infections

For dual coverage of both MRSA and streptococci, clindamycin alone is the preferred single-agent option, while TMP-SMX or a tetracycline (doxycycline/minocycline) combined with a beta-lactam (amoxicillin) provides effective dual coverage when clindamycin resistance is a concern. 1

Outpatient Treatment Approach

The treatment strategy depends critically on whether the infection is purulent or nonpurulent:

Purulent Cellulitis (with drainage/exudate but no drainable abscess)

• Primary target: MRSA coverage
• Empirical therapy for streptococci is likely unnecessary 1
• Oral antibiotic options:
  • Clindamycin 300-450 mg PO three times daily (covers both MRSA and strep) 1
  • TMP-SMX 1-2 double-strength tablets twice daily (MRSA only) 1
  • Doxycycline 100 mg PO twice daily (MRSA only) 1
  • Minocycline 200 mg loading dose, then 100 mg twice daily (MRSA only) 1
  • Linezolid 600 mg PO twice daily (covers both, but expensive) 1

Nonpurulent Cellulitis (no drainage/exudate, no abscess)

• Primary target: Streptococci coverage
• Add MRSA coverage only if patient fails beta-lactam therapy or has systemic toxicity 1
• Initial therapy:
  • Beta-lactam (cephalexin 500 mg four times daily or dicloxacillin) 1

If dual coverage needed from the start:

• Clindamycin alone 300-450 mg three times daily 1
• TMP-SMX or tetracycline PLUS amoxicillin 500 mg three times daily 1
• Linezolid alone 600 mg twice daily 1

Duration: 5-10 days, individualized based on clinical response 1

Hospitalized Patients with Complicated SSTI

For severe infections requiring IV therapy:

Empirical MRSA coverage options:

• Vancomycin 15-20 mg/kg/dose IV every 8-12 hours (A-I evidence) 1
• Linezolid 600 mg PO/IV twice daily (A-I evidence) 1
• Daptomycin 4 mg/kg/dose IV once daily (A-I evidence) 1
• Telavancin 10 mg/kg/dose IV once daily (A-I evidence) 1
• Clindamycin 600 mg IV/PO three times daily (A-III evidence) 1

Duration: 7-14 days based on clinical response 1

Pediatric Considerations

Critical age-related restrictions:

• Tetracyclines contraindicated in children <8 years old 1
• TMP-SMX not recommended in children <2 months or third-trimester pregnancy 1

Pediatric dosing for dual coverage:

• Clindamycin 10-13 mg/kg/dose every 6-8 hours (max 40 mg/kg/day) 1
• Linezolid:
  • Children >12 years: 600 mg twice daily
  • Children <12 years: 10 mg/kg/dose every 8 hours (max 600 mg/dose) 1

For hospitalized children with complicated SSTI, vancomycin is recommended (15 mg/kg/dose IV every 6 hours), with clindamycin as an alternative if clindamycin resistance is low (<10%) 1

Key Clinical Pitfalls

Avoid these common errors:

1. Don't use rifampin as monotherapy or adjunctive therapy for SSTI—no proven benefit and promotes resistance 1

2. Clindamycin resistance concerns: While clindamycin covers both pathogens, inducible resistance exists. Reserve for mild-moderate infections; avoid in severe infections if resistance detected 1

3. TMP-SMX and tetracyclines lack reliable streptococcal coverage—must add beta-lactam if strep coverage needed 1

4. Linezolid has higher adverse reaction rates compared to alternatives like teicoplanin, despite excellent efficacy 2

Evidence Quality Note

These recommendations come from the 2011 IDSA MRSA guidelines 1, 3 and 2014 IDSA SSTI guidelines 4, representing the highest-quality guideline evidence available. Recent network meta-analysis suggests linezolid may have superior clinical success rates compared to vancomycin for MRSA infections 2, though this doesn't change the guideline-based algorithmic approach for empirical dual coverage.