What antibiotics are used to treat cellulitis?

Antibiotic Treatment for Cellulitis

For typical non-purulent cellulitis, first-line treatment should be an antibiotic active against streptococci, such as penicillin, amoxicillin, dicloxacillin, cephalexin, or clindamycin for a 5-day course. 1, 2

First-Line Therapy Based on Severity

Mild to Moderate Cellulitis

• First-line therapy should target beta-hemolytic streptococci with oral antibiotics such as penicillin, amoxicillin, dicloxacillin, or cephalexin for 5 days 1, 2
• For patients with penicillin allergy, clindamycin or erythromycin are recommended alternatives 1
• Levofloxacin can be considered for patients with beta-lactam allergies, with similar efficacy demonstrated in 5-day treatment courses 1, 3

Severe Cellulitis

• For severe cellulitis or high-risk patients, consider coverage for methicillin-resistant Staphylococcus aureus (MRSA) 1, 2
• Indications for MRSA coverage include:
  • Penetrating trauma
  • Evidence of MRSA elsewhere
  • Nasal colonization with MRSA
  • Injection drug use
  • Purulent drainage
  • Systemic inflammatory response syndrome (SIRS) 1, 2
• Treatment options for severe cellulitis include:
  • Intravenous vancomycin
  • Daptomycin
  • Linezolid
  • Telavancin 1, 2

Combination Therapy Considerations

• If coverage for both beta-hemolytic streptococci and community-associated MRSA is desired, options include:
  • Clindamycin alone
  • Trimethoprim-sulfamethoxazole (TMP-SMX) in combination with a beta-lactam like amoxicillin
  • A tetracycline in combination with a beta-lactam 1
• In areas with high MRSA prevalence, antibiotics with activity against MRSA (such as TMP-SMX or clindamycin) have shown higher success rates compared to cephalexin 4

Treatment Duration

• A 5-day course is sufficient for uncomplicated cellulitis, with extension if no improvement is seen 1, 2, 3
• For severe cellulitis, treatment duration may be extended to 7-14 days based on clinical response 1

Pathogen Considerations

• Cellulitis is primarily caused by beta-hemolytic streptococci, with Staphylococcus aureus less frequently involved unless associated with penetrating trauma or underlying abscess 1, 5
• Most non-purulent, uncomplicated cases of cellulitis are caused by beta-hemolytic streptococci or methicillin-sensitive S. aureus 5
• Even in areas with high rates of community-acquired MRSA, coverage for MRSA in non-purulent cellulitis is generally not recommended unless specific risk factors are present 1, 5

Adjunctive Measures

• Elevate the affected area to promote gravity drainage of edema and inflammatory substances 1, 2
• Treat predisposing conditions such as edema, tinea pedis, or other toe web abnormalities 1, 2
• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adult patients to hasten resolution 1, 2

Common Pitfalls to Avoid

• Failure to examine interdigital toe spaces for fissuring, scaling, or maceration that may harbor pathogens 1
• Not elevating the affected area, which delays improvement 1
• Inadequate treatment duration when clinical improvement is not evident after 5 days 1
• Unnecessary MRSA coverage for typical non-purulent cellulitis in the absence of specific risk factors 1, 5