Cellulitis (including erysipelas)
Overview
Cellulitis and erysipelas are acute bacterial infections of the skin and subcutaneous tissues. Distinction is often clinical only: erysipelas is typically a well‑demarcated, raised, superficial plaque; cellulitis is usually more diffuse and deeper. Both range from mild, community‑managed infections to life‑threatening invasive disease.
Management is directed by severity, likely pathogens and exposure history (NICE NG141).
Microbiology and risk factors
Common pathogens
- Beta‑haemolytic streptococci, especially Streptococcus pyogenes.
- Staphylococcus aureus, including meticillin‑sensitive S. aureus (MSSA).
Atypical or exposure‑related organisms
- Pseudomonas spp. in immunocompromised hosts or specific exposures.
- Mixed Gram‑negative and anaerobic organisms after human or animal bites.
- Water‑associated organisms after freshwater or marine exposure.
Predisposing factors
- Lymphoedema.
- Venous insufficiency or venous eczema.
- Chronic leg skin disease (eg, stasis dermatitis).
- Tinea pedis or other interdigital fungal infection.