Recommended Antibiotic for Uncomplicated Skin Infection
For an uncomplicated community-acquired skin infection in an adult without drug allergies, use cephalexin 500 mg orally every 6 hours or penicillin/amoxicillin as first-line therapy.
Rationale and Treatment Algorithm
The majority of non-purulent, uncomplicated skin infections (cellulitis, erysipelas) are caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus 1. Beta-lactam antibiotics represent first-line therapy for most bacterial skin and soft tissue infections because they are efficacious, have well-defined adverse event profiles, and are cost-effective 2.
Specific Antibiotic Selection:
For classical erysipelas (streptococcal):
- Penicillin G or Penicillin V are recommended 2
- These target hemolytic streptococci specifically
For uncomplicated soft tissue infections from wounds (likely staphylococcal):
- Cephalexin (1st/2nd generation cephalosporin) 500 mg every 6 hours orally 3
- Alternatively: isoxazoyl penicillins (oxacillin/nafcillin) 2
- These provide appropriate S. aureus coverage
For mixed or uncertain etiology:
- Cephalexin 500 mg every 6 hours covers both streptococci and MSSA 3
- Amoxicillin is also appropriate for streptococcal coverage 1
Critical Clinical Caveat
Do NOT routinely cover for community-acquired MRSA in non-purulent cellulitis, even with rising MRSA rates 1. MRSA coverage (with agents like trimethoprim-sulfamethoxazole, doxycycline, or clindamycin) is reserved for:
- Purulent infections/abscesses
- Treatment failure with beta-lactams
- Known MRSA colonization
- Local epidemiology suggesting high MRSA prevalence
When Antibiotics Are NOT Needed
If the infection involves an abscess or furuncle with <5 cm of surrounding erythema and minimal systemic signs (temperature <38.5°C, WBC <12,000 cells/µL, pulse <100 bpm), incision and drainage alone is sufficient without antibiotics 3. Studies show little to no benefit for antibiotics when combined with adequate drainage in subcutaneous abscesses 3.
Duration Considerations
Recent evidence supports shorter antibiotic courses for uncomplicated infections 4, though specific duration should be guided by clinical response. Patients with temperature >38.5°C or heart rate >110 bpm may require only 24-48 hours of antibiotics if adequately drained 3.