What is the recommended antibiotic therapy for treating cellulitis?

Antibiotic Therapy for Cellulitis

For non-purulent cellulitis, a 5-6 day course of antibiotics active against streptococci is recommended as first-line therapy, with coverage for MRSA considered in patients who don't respond to beta-lactam therapy or have risk factors for MRSA infection. 1, 2

First-Line Treatment Options

Non-Purulent Cellulitis (No Drainage/Exudate/Abscess)

• First choice: Beta-lactam antibiotics targeting beta-hemolytic streptococci 1, 2
  • Amoxicillin-clavulanate
  • Cephalexin
  • Penicillin

When MRSA Coverage Is Needed

Consider MRSA coverage in patients who:

• Do not respond to beta-lactam therapy
• Have systemic toxicity
• Have risk factors for MRSA (prior MRSA infection, MRSA colonization, injection drug use)
• Have penetrating trauma

MRSA Coverage Options

• Clindamycin 600mg orally three times daily 1, 2
• Trimethoprim-sulfamethoxazole (TMP-SMX) 1
• Doxycycline or minocycline (not for children <8 years) 1, 2
• Linezolid 600mg twice daily 1

Combination Therapy Options

When coverage for both beta-hemolytic streptococci and MRSA is desired:

• Clindamycin alone 1, 2
• TMP-SMX plus a beta-lactam (e.g., amoxicillin) 1, 2
• Doxycycline plus a beta-lactam 2
• Linezolid alone 1

Treatment Duration

• 5-6 days for uncomplicated cellulitis 1, 2
• Consider extending if infection hasn't improved after 5 days 2
• Multiple studies show 5-day courses are as effective as 10-day courses 3

Hospitalized Patients with Complicated SSTI

For patients requiring hospitalization:

• IV vancomycin 1
• IV/oral linezolid 600mg twice daily 1
• Daptomycin 4mg/kg/day IV 1, 4
• Telavancin 10mg/kg/day IV 1
• IV clindamycin 600mg three times daily 1

Special Considerations

Pediatric Patients

• Mupirocin 2% topical ointment for minor skin infections 1
• Avoid tetracyclines in children <8 years 1, 2
• For hospitalized children with complicated SSTI, vancomycin is recommended 1
• Clindamycin 10-13mg/kg/dose IV every 6-8h is an option if local resistance is low 1

Adjunctive Therapy

• Consider systemic corticosteroids in select adult patients to hasten resolution (contraindicated in diabetics and pregnant women) 2
• Reduce underlying edema through elevation and compression stockings 2

Prevention of Recurrent Infections

• Keep draining wounds covered with clean, dry bandages 1
• Maintain good personal hygiene 1
• Avoid reusing or sharing personal items 1
• Consider environmental hygiene measures for recurrent SSTI 1
• Identify and treat predisposing conditions (edema, obesity, eczema, venous insufficiency) 2

Common Pitfalls to Avoid

1. Using TMP-SMX alone for non-purulent cellulitis (poor activity against streptococci) 2
2. Using tetracyclines in children under 8 years 1, 2
3. Failing to obtain cultures from abscesses and purulent drainage 1
4. Not considering MRSA coverage when risk factors are present 2
5. Using unnecessarily prolonged antibiotic courses when shorter durations are equally effective 1, 3

The evidence strongly supports a 5-6 day course of antibiotics for uncomplicated cellulitis, with the specific choice guided by local resistance patterns and patient-specific factors such as MRSA risk. Early recognition of treatment failure and appropriate adjustment of therapy are essential to improve outcomes and reduce complications.