What antibiotics are effective against Staphylococcus (Staph) aureus, including Methicillin-resistant Staphylococcus aureus (MRSA)?

Antibiotics Effective Against Staphylococcus aureus

The most effective antibiotics for treating Staphylococcus aureus infections depend on methicillin susceptibility, with first-line options including cloxacillin or cephalexin for MSSA and vancomycin, linezolid, or trimethoprim-sulfamethoxazole for MRSA. 1

Treatment Based on Methicillin Susceptibility

Methicillin-Susceptible S. aureus (MSSA)

• Oral options:

  • Dicloxacillin or cloxacillin (first choice) 1, 2
  • Cephalexin (first-generation cephalosporin) 1
  • Amoxicillin-clavulanic acid 1
  • Clindamycin (if penicillin allergic) 2

• Intravenous options:

  • Nafcillin or oxacillin (first choice) 1, 2
  • Cefazolin 1, 2
  • Clindamycin (if penicillin allergic) 2

Methicillin-Resistant S. aureus (MRSA)

• Oral options:

  • Trimethoprim-sulfamethoxazole (TMP-SMX) 1, 3
  • Clindamycin (if local resistance <10%) 1, 4
  • Doxycycline or minocycline 1, 3
  • Linezolid 1, 5
  • Tedizolid 1, 5

• Intravenous options:

  • Vancomycin (traditional first-line) 1, 6
  • Linezolid 1, 5, 7
  • Daptomycin (particularly for bacteremia and endocarditis) 1, 8, 3
  • Ceftaroline 1, 5, 7
  • Teicoplanin (where available) 2, 7
  • Tigecycline 1, 7
  • Dalbavancin (long-acting) 1, 5

Treatment Algorithm Based on Infection Severity

Mild Skin and Soft Tissue Infections

1. For suspected MSSA:

   • Dicloxacillin or cephalexin for 7 days 1

2. For suspected or confirmed MRSA:

   • Trimethoprim-sulfamethoxazole (TMP-SMX) 1, 4
   • Doxycycline as alternative 1, 3
   • Clindamycin if local resistance rates are low (<10%) 1, 4

Moderate to Severe Infections

1. For suspected MSSA:

   • IV nafcillin, oxacillin, or cefazolin 1, 2

2. For suspected or confirmed MRSA:

   • IV vancomycin (15 mg/kg q12h) 1
   • IV daptomycin (4-6 mg/kg q24h) for bacteremia and endocarditis 1, 8
   • IV linezolid (600 mg q12h) particularly for pneumonia and complicated skin infections 1, 5

Necrotizing Infections

• Combination therapy recommended:
  • Clindamycin plus piperacillin-tazobactam (with or without vancomycin) 1
  • Ceftriaxone plus metronidazole (with or without vancomycin) 1

Special Considerations

Treatment Duration

• Uncomplicated skin infections: 5-10 days 4
• Bacteremia: Minimum 2 weeks for uncomplicated cases, 4-6 weeks for complicated cases 4

Surgical Management

• Incision and drainage is crucial for purulent infections and should be performed whenever feasible 4, 1
• Obtaining cultures from purulent drainage before starting antibiotics helps guide definitive therapy 4

Antibiotic Selection Considerations

• Vancomycin is becoming less effective for MRSA with higher MICs within the susceptible range 7, 6
• Linezolid has shown superior efficacy compared to vancomycin for MRSA skin infections and pneumonia 1, 5
• Daptomycin should not be used for pneumonia due to inactivation by pulmonary surfactant 5

Common Pitfalls to Avoid

• Using beta-lactam antibiotics alone for MRSA infections 4
• Failing to drain abscesses when present, which can lead to treatment failure regardless of antibiotic choice 4
• Using daptomycin for MRSA pneumonia 5
• Using clindamycin empirically in areas with high resistance rates 4

Prevention of Recurrence

• Keep draining wounds covered with clean, dry bandages 4
• Maintain good personal hygiene with regular handwashing 4
• Consider decolonization with mupirocin (nasal) and chlorhexidine (body) for recurrent infections 4