Cellulitis and Skin Infections

Cellulitis & Skin Infections

Cellulitis is a spreading infection of the skin extending to involve the subcutaneous tissues. The most common causes are group A b -haemolytic streptococci (GABHS) and Staphylococcus aureus. Predisposing factors include skin abrasions, lacerations, burns, eczematous skin, etc, although the portal of entry of organisms is often not seen.

Allergic reactions / contact dermatitis (e.g. to insect bites, immunisations, plants, etc) are frequently misdiagnosed as cellulitis. If there is itchiness and no tenderness, cellulitis is unlikely.

Erysipelas is a specific superficial form of cellulitis usually caused by GABHS. There may be lymphatic involvement.

Impetigo (commonly called "school sores") is a highly contagious infection of the epidermis, particularly common in young children. Causative organisms are GABHS and S. aureus.

Staphylococcal scalded skin syndrome (SSSS) is a blistering skin disorder induced by the exfoliative (epidermolytic) toxins of S. aureus. It primarily affects neonates and young children.

Necrotising fasciitis is a rapidly progressive soft tissue infection characterised by necrosis of subcutaneous tissue. Aetiology is often polymicrobial. Causative organisms include GABHS, S. aureus, anaerobes, etc. It can cause severe illness with a high mortality rate (ﾒ 25%).

Consider herpetic infection when vesicles are present, and send appropriate specimens for immunofluorescence and viral culture.

There are many other forms of skin infection that are not covered in this guideline.

Assessment

The typical presenting features of all skin infections include soft tissue redness, warmth and swelling, but other features are variable (see table and photos below). It is difficult to distinguish between skin infections caused by GABHS and S. aureus on a clinical basis alone.

Investigations

Swab for Gram stain (slide) and culture if discharge present
FBE + blood culture if systemic symptoms present
ESR, xrays +/- bone scan if osteomyelitis suspected (See Osteomyelitis / Septic arthritis guidelines)
Ultrasound if fluctuance present

Treatment

Flucloxacillin 25 mg/kg (max 500mg) po 6H for 7 days

If severe/extensive, systemically unwell or not responding to oral treatment
flucloxacillin 50 mg/kg (max 2g) iv 6H(consider adding clindamycin if rapidly progressive to inhibit toxin production)

For facial/periorbital cellulitis: consider adding cefotaxime if: <>Periorbital cellulitis guidelines)

See complete article with diagnostic images:

Cellulitis and Skin Infections