What is the recommended treatment for cellulitis?

Treatment of Cellulitis

For typical cases of cellulitis without systemic signs of infection, an antimicrobial agent active against streptococci should be used as first-line therapy, with a recommended duration of 5 days, extending treatment if the infection has not improved within this period. 1

Classification and Initial Assessment

Cellulitis severity can be classified into three categories that guide treatment:

• Mild (without systemic signs): Localized infection without systemic symptoms
• Moderate (with systemic signs): Infection with fever, tachycardia, or other systemic symptoms
• Severe: Infection with SIRS, altered mental status, hemodynamic instability, or in immunocompromised patients

Key diagnostic considerations:

• Examine interdigital toe spaces in lower-extremity cellulitis to identify and treat fissuring, scaling, or maceration 1
• Differentiate from mimickers such as venous stasis dermatitis, contact dermatitis, and lymphedema 2
• Cultures are not routinely recommended for typical cases but should be obtained in:
  • Patients with malignancy on chemotherapy
  • Neutropenia
  • Severe cell-mediated immunodeficiency
  • Immersion injuries
  • Animal bites 1

Antimicrobial Treatment Algorithm

1. Mild Cellulitis (without systemic signs)

• First-line: Oral antibiotic active against streptococci 1
  • Penicillin VK 250-500 mg every 6 hours
  • Cephalexin 500 mg four times daily 3
  • Amoxicillin 500 mg three times daily

2. Moderate Cellulitis (with systemic signs)

• First-line: Systemic antibiotics active against streptococci with consideration for MSSA coverage 1
  • Cephalexin 1g four times daily 3
  • Dicloxacillin 500 mg four times daily
• Consider hospitalization if outpatient treatment is failing

3. Severe Cellulitis or Special Circumstances

• For MRSA risk factors (penetrating trauma, evidence of MRSA elsewhere, nasal colonization with MRSA, injection drug use, or SIRS):

  • Vancomycin or another antimicrobial effective against both MRSA and streptococci 1
  • Linezolid 600 mg IV or oral twice daily (10-14 days) 4

• For severely compromised patients:

  • Vancomycin plus either piperacillin-tazobactam or imipenem/meropenem 1

Duration of Treatment

• Standard duration: 5 days 1
• Extend treatment if infection has not improved within 5 days 1
• Reassess after 48-72 hours to evaluate response 3

Adjunctive Measures

• Elevate the affected area 1
• Treat predisposing factors such as edema or underlying cutaneous disorders 1
• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adult patients 1

Hospitalization Criteria

Hospitalization is recommended if:

• There is concern for deeper or necrotizing infection
• Poor adherence to therapy is anticipated
• Infection is in a severely immunocompromised patient
• Outpatient treatment is failing 1

Prevention of Recurrence

• Identify and treat predisposing conditions: edema, obesity, eczema, venous insufficiency, and toe web abnormalities 1
• For patients with 3-4 episodes per year despite addressing predisposing factors, consider prophylactic antibiotics:
  • Oral penicillin or erythromycin twice daily for 4-52 weeks
  • Intramuscular benzathine penicillin every 2-4 weeks 1, 3

Important Clinical Pearls

• Beta-hemolytic streptococci remain the primary cause of diffuse, nonculturable cellulitis (73% of cases) 5
• Despite rising rates of community-acquired MRSA, coverage for non-purulent cellulitis is generally not recommended unless specific risk factors are present 2
• Treatment with beta-lactam antibiotics remains effective for diffuse, nonculturable cellulitis with a response rate of approximately 96% 5
• Recurrent cellulitis is common due to persistent post-inflammatory lymphatic damage 6

Remember that early and appropriate antimicrobial therapy targeting the most likely pathogens based on clinical presentation is essential for reducing morbidity and mortality associated with cellulitis.