What is the best antibiotic for an uncomplicated abrasion infection in an otherwise healthy individual?

Best Antibiotic for Abrasion Infection

For an uncomplicated abrasion infection in an otherwise healthy individual, cephalexin 500 mg orally four times daily for 7 days is the most appropriate first-line antibiotic, providing excellent coverage against the most common pathogens: Staphylococcus aureus and Streptococcus pyogenes.

Understanding the Pathogen Profile

Abrasion infections are primarily caused by skin flora, with S. aureus and S. pyogenes being the predominant pathogens 1. In pediatric studies of skin infections, these two organisms accounted for the vast majority of cultured pathogens, with microbiologic eradication rates exceeding 97% with appropriate beta-lactam therapy 1.

First-Line Treatment: Cephalexin

Cephalexin remains the gold standard for uncomplicated skin infections because it provides targeted coverage against methicillin-susceptible S. aureus (MSSA) and streptococcal species 1, 2. The standard dosing is 500 mg orally four times daily for 7-10 days 1.

• Clinical cure rates with cephalexin for uncomplicated skin infections range from 93.8% to 98.3% 1
• Cephalexin is well-tolerated, with diarrhea being the most common adverse event (4% incidence) 1
• The four-times-daily dosing ensures adequate tissue penetration throughout the day 1

Alternative First-Line Options

For patients who cannot tolerate four-times-daily dosing, cefdinir 7 mg/kg twice daily (or 300 mg twice daily for adults) for 10 days is an excellent alternative 1. Cefdinir demonstrated a 99.4% microbiologic eradication rate and 98.3% clinical cure rate in pediatric skin infections, with the advantage of twice-daily dosing 1.

Cefditoren pivoxil 200 mg twice daily for 10 days is another alternative, achieving 89% clinical cure rates for uncomplicated skin infections caused by S. aureus and S. pyogenes 2. This agent has excellent activity against penicillin-susceptible and -intermediate S. pneumoniae, S. pyogenes, and methicillin-susceptible S. aureus 2.

When NOT to Add MRSA Coverage

Do not routinely add trimethoprim-sulfamethoxazole or other MRSA-active agents for simple abrasions without purulent drainage. A large randomized trial demonstrated that adding trimethoprim-sulfamethoxazole to cephalexin provided no additional benefit for uncomplicated cellulitis, with clinical cure rates of 83.5% for combination therapy versus 85.5% for cephalexin alone (difference -2.0%, 95% CI -9.7% to 5.7%) 3.

For abscesses requiring incision and drainage, antibiotics may be unnecessary altogether—a placebo-controlled trial showed 90.5% cure rates with drainage alone, even when 87.8% of isolates were MRSA 4. However, simple abrasions without abscess formation differ from this scenario and benefit from appropriate antibiotic coverage.

Treatment Duration

The standard treatment duration is 7-10 days 1, 2. Shorter courses risk treatment failure and recurrence, while longer courses provide no additional benefit and increase adverse events 1.

Penicillin-Allergic Patients

For patients with documented penicillin allergy:

• Cefdinir or cefditoren remain appropriate choices if the allergy is non-severe (non-anaphylactic), as cross-reactivity risk with third-generation cephalosporins is negligible 2
• For severe penicillin allergy with anaphylaxis history, consider alternative agents outside the beta-lactam class, though specific guidelines for simple abrasions in this context are limited in the provided evidence

Critical Pitfalls to Avoid

• Do not use first-generation cephalosporins for infections requiring gram-negative coverage, but for simple skin abrasions where S. aureus and S. pyogenes predominate, cephalexin is ideal 1
• Do not add MRSA coverage empirically unless there is purulent drainage, abscess formation, or systemic signs of severe infection 4, 3
• Do not use inadequate treatment duration—complete the full 7-10 day course even if symptoms improve earlier 1
• Ensure the wound is properly cleaned and debrided before initiating antibiotics, as mechanical cleansing is essential for infection control 5

When to Escalate Therapy

Reassess the patient at 48-72 hours. If there is:

• Worsening erythema, swelling, or tenderness
• Fever development
• Purulent drainage
• Systemic symptoms

Consider broader coverage, obtain wound cultures, and evaluate for abscess formation requiring drainage 3.