Cellulitis

Cellulitis is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Acute, spreading erythematous superficial infection of skin and SC tissues:
    • Nonpurulent SSTI (skin and soft tissue infection) = uncomplicated cellulitis
    • Purulent SSTI = cellulitis with purulent component is covered in “Abscess”
    • Extension into deeper tissues can result in necrotizing soft tissue infection
  • Progressive spread of erythema, warmth, pain, and tenderness
  • Predisposing factors:
    • Lymphedema
    • Tinea pedis or other toe web abnormalities
    • Open wounds
    • Pre-existing skin lesion (furuncle)
    • Prior trauma or surgery
    • Retained foreign body
    • Vascular or immune compromise
    • Injection drug use
    • Recurrent SSTI

Etiology

  • Uncomplicated cellulitis (nonpurulent SSTI):
    • Group A streptococci
    • Methicillin-sensitive Staphylococcus aureus (MSSA)
    • Methicillin-resistant S. aureus (MRSA)
    • Risk factors for Staph infection (MSSA and MRSA):
      • Recent hospital or long-term care admission
      • Recent surgery
      • Children
      • Soldiers
      • Incarcerated persons
      • Athletes in contact sports
      • Injection drug use
      • Men who have sex with men
      • Dialysis treatments and catheters
      • History of penetrating trauma
    • Additional risk factors for MRSA infection:
      • Prior MRSA infection
      • MRSA colonization
      • Area of high MRSA incidence
      • Close contact with MRSA patient
  • Extremity cellulitis after lymphatic disruption:
    • Nongroup A β-hemolytic streptococci (groups C, B, G)
  • Cellulitis in diabetics:
    • Can be polymicrobial with S. aureus, streptococci, gram-negative bacteria, and anaerobes, especially when associated with skin ulcers
  • Periorbital cellulitis:
    • Strep and Staph
  • Buccal cellulitis:
    • Polymicrobial with anaerobic oral flora, associated with intraoral laceration or dental abscess
  • Less common causes:
    • Clostridia
    • Anthrax
    • Pasteurella multocida – common after cat and dog bites
    • Eikenella corrodens – human bites
    • Pseudomonas aeruginosa:
      • Hot-tub folliculitis – self-limited
      • Foot puncture wound
      • Ecthyma gangrenosum in neutropenic patients
    • Erysipelothrix species – saltwater fish, poultry, meat, or hide handlers
    • Aeromonas hydrophila – freshwater swimming
    • Vibrio species – seawater or raw seafood

Pediatric Considerations
  • Facial cellulitis in children:
    • Streptococcus pneumoniae
    • H. influenzae type B, although incidence significantly declining since introduction of HIB vaccine
  • Perianal cellulitis:
    • Group A streptococci
    • Associated or antecedent pharyngitis or impetigo
  • Neonates:
    • Group B streptococci

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Basics

Description

  • Acute, spreading erythematous superficial infection of skin and SC tissues:
    • Nonpurulent SSTI (skin and soft tissue infection) = uncomplicated cellulitis
    • Purulent SSTI = cellulitis with purulent component is covered in “Abscess”
    • Extension into deeper tissues can result in necrotizing soft tissue infection
  • Progressive spread of erythema, warmth, pain, and tenderness
  • Predisposing factors:
    • Lymphedema
    • Tinea pedis or other toe web abnormalities
    • Open wounds
    • Pre-existing skin lesion (furuncle)
    • Prior trauma or surgery
    • Retained foreign body
    • Vascular or immune compromise
    • Injection drug use
    • Recurrent SSTI

Etiology

  • Uncomplicated cellulitis (nonpurulent SSTI):
    • Group A streptococci
    • Methicillin-sensitive Staphylococcus aureus (MSSA)
    • Methicillin-resistant S. aureus (MRSA)
    • Risk factors for Staph infection (MSSA and MRSA):
      • Recent hospital or long-term care admission
      • Recent surgery
      • Children
      • Soldiers
      • Incarcerated persons
      • Athletes in contact sports
      • Injection drug use
      • Men who have sex with men
      • Dialysis treatments and catheters
      • History of penetrating trauma
    • Additional risk factors for MRSA infection:
      • Prior MRSA infection
      • MRSA colonization
      • Area of high MRSA incidence
      • Close contact with MRSA patient
  • Extremity cellulitis after lymphatic disruption:
    • Nongroup A β-hemolytic streptococci (groups C, B, G)
  • Cellulitis in diabetics:
    • Can be polymicrobial with S. aureus, streptococci, gram-negative bacteria, and anaerobes, especially when associated with skin ulcers
  • Periorbital cellulitis:
    • Strep and Staph
  • Buccal cellulitis:
    • Polymicrobial with anaerobic oral flora, associated with intraoral laceration or dental abscess
  • Less common causes:
    • Clostridia
    • Anthrax
    • Pasteurella multocida – common after cat and dog bites
    • Eikenella corrodens – human bites
    • Pseudomonas aeruginosa:
      • Hot-tub folliculitis – self-limited
      • Foot puncture wound
      • Ecthyma gangrenosum in neutropenic patients
    • Erysipelothrix species – saltwater fish, poultry, meat, or hide handlers
    • Aeromonas hydrophila – freshwater swimming
    • Vibrio species – seawater or raw seafood

Pediatric Considerations
  • Facial cellulitis in children:
    • Streptococcus pneumoniae
    • H. influenzae type B, although incidence significantly declining since introduction of HIB vaccine
  • Perianal cellulitis:
    • Group A streptococci
    • Associated or antecedent pharyngitis or impetigo
  • Neonates:
    • Group B streptococci

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