What antibiotics are recommended for strep and skin infections, including those caused by methicillin-resistant Staphylococcus aureus (MRSA)?

Antibiotic Recommendations for Streptococcal and Staphylococcal Skin Infections

For streptococcal and staphylococcal skin infections, including MRSA, first-line treatment should be clindamycin (600-900 mg every 8 hours IV for severe infections or 300-450 mg PO three times daily for less severe infections) or trimethoprim-sulfamethoxazole for confirmed MRSA infections. 1

Treatment Algorithm for Skin Infections

Non-MRSA Streptococcal and Staphylococcal Infections

1. First-line options:

   • Penicillinase-resistant penicillins:

     • Dicloxacillin 500 mg PO four times daily
     • Nafcillin 1-2 g IV every 4 hours (for severe infections)
     • Oxacillin 1-2 g IV every 4 hours (for severe infections) 2

   • First-generation cephalosporins:

     • Cephalexin 500 mg PO every 6-12 hours for 7-10 days 3
     • Cefazolin 1 g IV every 8 hours (for severe infections) 2

2. For penicillin-allergic patients:

   • Clindamycin 300-450 mg PO three times daily or 600-900 mg IV every 8 hours 2, 1
   • Doxycycline 100 mg PO twice daily (for patients >8 years old) 1

MRSA Infections

1. Outpatient treatment (mild-moderate infections):

   • Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 DS tablets twice daily 1, 4
   • Clindamycin 300-450 mg PO three times daily (if local resistance <10%) 1, 4
   • Doxycycline or minocycline 100 mg PO twice daily 1, 4
   • Linezolid 600 mg PO twice daily (reserve for serious infections or treatment failures) 1, 5

2. Inpatient treatment (severe infections):

   • Vancomycin 15-20 mg/kg IV every 8-12 hours (not to exceed 2g per dose) 2, 1
   • Linezolid 600 mg IV/PO twice daily 1
   • Daptomycin 6-10 mg/kg IV once daily 1

Special Considerations

Mixed Infections

For mixed infections involving both streptococci and other organisms, broader coverage may be needed:

• Ampicillin-sulbactam 1.5-3.0 g IV every 6-8 hours
• Piperacillin-tazobactam 3.37 g IV every 6-8 hours plus clindamycin and ciprofloxacin 2

Necrotizing Infections

For necrotizing streptococcal infections:

• Penicillin 2-4 MU IV every 4-6 hours plus clindamycin 600-900 mg IV every 8 hours 2

Pediatric Dosing

• For children: Cephalexin 25-50 mg/kg/day divided in 4 doses 3
• For children <8 years: Avoid tetracyclines; use amoxicillin-clavulanate, cephalexin, or clindamycin 1
• Clindamycin dosing for children: 10-13 mg/kg/dose every 6-8 hours (not exceeding 40 mg/kg/day) 1

Treatment Duration

• For uncomplicated skin infections: 7-10 days
• For streptococcal pharyngitis: Minimum 10 days to prevent rheumatic fever 3
• For MRSA bacteremia: Minimum 14 days 1
• For complicated infections (osteomyelitis, endocarditis): 4-6 weeks 1

Important Clinical Pearls

1. Antibiotic resistance considerations:

   • Most S. aureus strains are now resistant to penicillin 5
   • Community-acquired MRSA may have different susceptibility patterns than hospital-acquired MRSA 1, 4
   • Always check local resistance patterns when selecting empiric therapy

2. Monitoring:

   • Follow-up cultures should be obtained 2-4 days after initial positive cultures in bacteremia 1
   • Monitor for adverse effects, particularly with clindamycin (C. difficile), TMP-SMX (rash, hyperkalemia), and linezolid (bone marrow suppression, peripheral neuropathy) 1

3. Combination therapy:

   • For multi-resistant MRSA, combination therapy (e.g., rifampicin plus fusidic acid) may be necessary to prevent resistance development 5

4. Newer agents:

   • Reserve newer agents like linezolid, daptomycin, and quinupristin/dalfopristin for serious infections or treatment failures 5, 6

5. Adjunctive measures:

   • Incision and drainage remains critical for purulent infections
   • Implement infection control measures to prevent MRSA spread 1

By following this evidence-based approach to antibiotic selection for streptococcal and staphylococcal skin infections, clinicians can optimize treatment outcomes while minimizing the risk of antibiotic resistance.