Cellulitis

Introduction

• Erythema, edema, warmth, tender ± fever and adenopathy
• Usually unilateral lower extremities
  • Bilateral may be due to stasis dermatitis, lymphedema, or lipodermatosclerosis
• Risk:
  • Loss of skin integrity
    • Trauma
    • Insect/animal bite
    • Skin disorders (psoriasis, eczema)
    • Skin infection (Tinea) or ulcer
  • Immunocompromised (Diabetes)
  • Edema or vascular disease
    • Lymph/venous stasis
• Most common pathogens beta-hemolytic streptococci (non-purulent) and S. aureus (purulent)
  • Erysipelas (superficial sharply demarcated) usually group A streptococcus

Investigations

• Clinically assess for:
  • Necrotizing fasciitis – Pain out of proportion, check scrotum for Fournier gangrene
    • Surgical debridement and empiric antibiotics (Tazo/Clinda/Vanco IV)
  • Toxic shock syndrome – Pain prior to physical findings, ecchymoses, sloughing skin, hypotensive
    • Fluids and vasopressors for hypotension, surgical debridement, empiric antibiotics and IVIG
  • Gas gangrene (clostridial myonecrosis) – Fever, severe pain after surgery/trauma, crepitus
    • Surgery (debridement) and empiric antibiotics ± hyperbaric oxygen
  • Orbital cellulitis – Limitation and/or pain with eye movements, proptosis, visual changes, edema beyond eyelid, history of acute sinusitis/surgery/trauma, no improvement in 24-48 hours
    • Rule out extension/abscess with CT, referral to ophthalmology
  • Labs: WBC, CRP, creatinine, CPK, glucose (rule out diabetes in repeated infections)
  • Culture of pus
  • Culture Blood (low yield ~5%) if toxic, extensive, comorbidities, special exposures, recurrent, or persistent infection
  • X-ray to rule out foreign body
  • Ultrasound may show marbling/cobblestoning
  • Rule out skin abscess, gas gangrene, thrombosis
  • MRI to rule out osteomyelitis

Treatment

• Elevation of affected area (drain edema)
• Promote optimal hydration of skin without maceration
• Consider compressive stockings and diuretic therapy for lymphedema and chronic venous insufficiency

Parenteral (IV) antibiotics if signs of systemic toxicity, rapid progression of erythema, immunocompromised, indwelling device or if progression of symptoms despite 48-72 hours of appropriate oral therapy

• Purulent cellulitis with known MRSA (or requires coverage)
  • Vancomycin 15 to 20mg/kg/dose IV q8-12h (max 2g per dose)
  • Daptomycin 4 to 6mg/kg IV q24h
  • Clindamycin 900mg IV q8h
  • Linezolid 600mg IV q12h
• Nonpurulent cellulitis or purulent with no MRSA risk factors (eg. previous MRSA, highly prevalent environment, recurrent infection) should cover for beta-hemolytic streptococci and MSSA
  • Cefazolin 1 to 2g IV q8h
  • Clindamycin 900mg IV q8h
  • Naficillin or Oxacillin 2g IV q4h
• Pseudomonas coverage (if inadequate response, immunocompromised, prior infection)
  • Cefepime 2g IV q12h
  • Ceftazidime 1g IV q8h
  • Piperacillin-Tazobactam 3.375g IV q6h
  • Imipenem 500mg IV q6h
  • Meropenem 1g IV q8h

Oral Antibiotics

• Purulent cellulitis with known MRSA (or requires coverage)
  • TMP-SMX [Septra DS] 1-2 double-strength tabs BID
  • Doxycycline 100mg PO BID
  • Minocycline 200 mg PO once, then 100 mg PO BID
  • Clindamycin 300 to 450 mg PO q8h
• Nonpurulent with no MRSA risk factors should cover for beta-hemolytic streptococci and MSSA
  • Dicloxacillin 500 mg PO q6h
  • Amoxicillin 500 mg PO q8h
  • Cefadroxil 1 g PO daily (or BID)
  • Cephalexin 500 mg PO QID (or BID)
    • In children 50-100mg/kg/day PO div TID (max 3000-4500mg/day)
  • For penicillin allergic except those with immediate hypersensitivity consider Clarithromycin 500mg PO BID or Clindamycin
• Dog/Cat/Human Bites should cover for both aerobic and anaerobic bacteria
  • Amoxicillin-clavulanate [Clavulin] 875/125mg PO BID
  • Doxycycline 100mg PO BID
    • For penicillin allergic and to cover for MRSA
  • Delayed wound closure, unless face <24h and clearly uninfected
  • Consider postexposure prophylaxis for rabies
    • Monitor animal for 10 days for rabies, if wild animal call Public health or give prophylaxis
  • Consider tetanus
• Exposure to water should cover for AEEVM (Aeromonas species, Edwardsiella tarda, Erysipelothrix rhusiopathiae, Vibrio vulnificus, and Mycobacterium marinum)
  • Cephalexin 500mg PO q6h or Cefazolin 1g IV q8h or Clindamycin (if pen-allergic)
    • PLUS Levofloxacin 750mg PO daily
    • PLUS Metronidazole if soil-contaminant (covered by clindamycin)
    • PLUS Doxycycline if seawater exposure (to cover for Vibrio species)

Duration of therapy: 5 days if uncomplicated, extend up to 14 days if severe or slow response to therapy