Cellulitis Classification and Diagnosis

Diagnostic Criteria

A wound infection with surrounding erythema is considered cellulitis according to established clinical definitions and guidelines from the Infectious Diseases Society of America (IDSA) 1, 2
Cellulitis is defined as a diffuse, superficial, spreading skin infection that presents with erythema (redness) extending beyond the immediate wound margins, warmth of the affected area, tenderness or pain, swelling or induration, and sometimes accompanied by lymphangitis and regional lymph node inflammation 2
The IDSA specifically includes "wound infection surrounded by erythema" in their classification of skin and soft tissue infections, categorizing it as a form of cellulitis 3, 4, 5

The International Working Group on the Diabetic Foot (IWGDF) and IDSA classification system notes that infection involving the skin or subcutaneous tissue with local signs such as local swelling or induration, erythema >0.5 cm around the wound, local tenderness or pain, and local warmth constitutes an infected wound with cellulitis 6
Purulent discharge is also a sign of infected wound with cellulitis 7

For wound infections with surrounding cellulitis, both drainage (if applicable) and systemic antimicrobial therapy are required, with antibiotic selection targeting streptococci and Staphylococcus aureus as the most common causative organisms 1, 2
Appropriate antibiotic duration for cellulitis with wound infection is typically 5-10 days, with extension if symptoms haven't improved 3, 4

The presence of erythema alone is not sufficient for diagnosis of cellulitis - the clinical context and other signs of infection must be considered together 2, 6