- Infection of superficial skin and skin structures
Etiology
- Streptococcus pyogenes (much more common)
- Staphylococcus aureus (especially if purulent)
- Rare, depending on exposures:
- Hand or foot puncture: Pseudomonas aeruginosa
- Facial cellulitis in children: Haemophilus influenzae
- Human bite wounds: Anaerobes, Eikenella, viridans-group Streptococcus
- Cat or dog bites: Pasteurella multocida
- Saltwater exposure: Vibrio vulnificus (e.g. injury on coral)
- Fresh- or saltwater exposure: Aeromonas hydrophila (e.g. leech bites)
- Butchers: Erysipelothrix (erysipeloid)
Differential Diagnosis
- Skin and soft tissue infections
- Cellulitis (Strep/Staph)
- Erysipelas (usually Strep)
- Abscess (usually Staph)
- Folliculitis (usually Staph or Pseudomonas): warm compresses and mupirocin ointment
- Impetigo (usually Staph): watchful waiting, or topical or systemic antibiotics
- Carbuncles
- Necrotizing fasciitis
- Other disease
- Deep vein thrombosis
- Gout (if over a joint)
- Erythema nodosum
- For an exhaustive list, see [Cellulitis mimickers](Cellulitis mimickers.md)
Presentation
- Hot, red, swollen, tender area of skin with poorly demarcated margins
- With or without pus and/or bullae
- Legs more common than elsewhere
Management
- Source control: drain any abscess
- Antibiotics for 5-7 days
- Purulent SSTI
- Cephalexin or cefazolin are good first-line empiric choices
- Doxycycline or vancomycin can also be considered
- Non-purulent SSTI
- Cephalexin 500mg po qid or cefazolin 1-2g IV q8h for 5-7 days
- If penicillin allergy
- Clindamycin300mg po qid
- Moxifloxacin 400mg po daily
- Linezolid 600mg po bid
- Clindamycin 600mg IV tid
- Vancomycin 1g IV q12h
- Non-resolving cellulitis
- Bug-drug mismatch
- Resistance
- Poor antibiotic choice
- Unusual organism
- Water exposure (fresh- or saltwater)
- Fish
- Shellfish, meats, hides
- IV drug use
- Animal or human bites
- Poor adherence/absorption/distribution
- Wrong diagnosis
- Impatience!
- Complications of infection
- Abscess (drain it)
- Deep infection
- Metastasis
Prophylaxis
