Bacterial skin infection of lower dermis and subcut tissue

<aside> 💡 dont draw margin around it - lagging indicator of cell damage. local damage can worsen even 48hrs after therapy. (systemic Sx should have eased)

</aside>

Aetiology

many people falsely attribute to unseen spider bite

• 2/3 strep pyo
• 1/3 staph aureus
• rare causes:
  • Pseudomonas aeruginosa, usually in a puncture wound of foot or hand
  • Haemophilus influenzae, in children with facial cellulitis
  • Anaerobes, Eikenella, Streptococcus viridans, due to human bite
  • Pasteurella multocida, due to cat or dog bite
  • Vibrio vulnificus, due to saltwater exposure, eg coral injury
  • Aeromonas hydrophila from fresh or saltwater exposure, eg following leech bites
  • Erysipelothrix (erysipeloid), in butchers.

Risk Factors

• PHx
• fissuring of heels or toes
• venous disease
• injury
• immunosuppression
• diabetes