What is the recommended treatment for cellulitis?

Treatment of Cellulitis

The first-line treatment for uncomplicated cellulitis is amoxicillin-clavulanate 875/125 mg twice daily orally for 5-7 days, which provides coverage for both beta-hemolytic streptococci and Staphylococcus aureus, the most common causative pathogens. 1

Causative Organisms and Antibiotic Selection

Cellulitis is an infection of the deep dermis and subcutaneous tissue that presents with expanding erythema, warmth, tenderness, and swelling. The majority of cases are caused by:

• Beta-hemolytic streptococci (primary pathogen)
• Staphylococcus aureus (including MRSA in specific risk groups)

First-line Treatment Options:

• Amoxicillin-clavulanate 875/125 mg twice daily orally for 5-7 days
• Cephalexin 500 mg 3-4 times daily for 5-7 days (for non-purulent cellulitis)

Alternative Options (for penicillin allergies):

• Clindamycin 300-450 mg orally three times daily for 5-7 days
• Doxycycline 100 mg twice daily (good activity against Pasteurella multocida)
• Trimethoprim-sulfamethoxazole (160-800 mg twice daily) plus metronidazole (250-500 mg three times daily)

MRSA Coverage Considerations

MRSA coverage should be considered in patients with:

• Previous MRSA infection or colonization
• Purulent cellulitis
• Failure to respond to beta-lactam therapy
• High-risk groups: athletes, children, men who have sex with men, prisoners, military recruits, residents of long-term care facilities, intravenous drug users 1

For MRSA coverage, options include:

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily
• Linezolid 600 mg twice daily (for severe infections or treatment failures) 2
• Clindamycin 300-450 mg three times daily (if local resistance rates are low)

Duration of Therapy

• Standard treatment duration: 5-7 days for uncomplicated infections 1
• Extended treatment (7-10 days) for:
  • Established infections
  • Immunocompromised patients
  • Patients with comorbidities (diabetes, peripheral vascular disease)
  • Severe or extensive disease

Treatment should continue until at least 48-72 hours after resolution of symptoms 3

Special Considerations

Recurrent Cellulitis

For patients with recurrent cellulitis, address underlying risk factors:

• Treat tinea pedis or other fungal infections
• Manage lymphedema with compression therapy
• Treat venous insufficiency
• Consider prophylactic antibiotics (penicillin V) for frequent recurrences 4

Adjunctive Therapy

• Elevation of affected limb
• Pain control
• Consider anti-inflammatory agents (ibuprofen 400 mg every 6 hours) which may hasten resolution of inflammation 5

Treatment Failure

If no improvement after 48-72 hours of appropriate therapy:

1. Reassess diagnosis (consider conditions that mimic cellulitis)
2. Consider ultrasound to rule out abscess formation
3. Broaden antibiotic coverage
4. Consider hospitalization for IV antibiotics

Monitoring and Follow-up

• Patients should show improvement within 48-72 hours of starting antibiotics
• Mark the border of erythema to monitor progression/resolution
• Follow up within 48-72 hours for non-improving patients
• Complete resolution typically occurs within 7-10 days

Research shows that adding trimethoprim-sulfamethoxazole to cephalexin for uncomplicated cellulitis does not significantly improve outcomes in most patients, suggesting that routine MRSA coverage is unnecessary for typical cases 6, 7.