Classification and Management of Skin and Soft Tissue Infections

Classification by Purulence and Severity

The Infectious Diseases Society of America (IDSA) classifies skin and soft tissue infections based on three main characteristics: presence of purulence, clinical severity, and presence of tissue necrosis 1, 2
Mild purulent infections are localized without systemic signs of infection, and patients have no significant comorbidities, requiring only incision and drainage without antibiotics in most cases 1, 2
Moderate purulent infections present with systemic signs of infection, such as fever, tachycardia, tachypnea, or abnormal white blood cell count, and require incision and drainage plus systemic antibiotics 1, 2, 3
Severe purulent infections are characterized by failure of incision and drainage plus oral antibiotics, presence of systemic signs of infection, and patients may be immunocompromised or have signs of deep infection 1, 2, 3

The Eron classification system divides infections into four classes based on systemic toxicity and comorbidities: Class 1 (no systemic toxicity or comorbidities), Class 2 (systemically ill with stable comorbidities or well but with complicating comorbidity), Class 3 (toxic appearance), and Class 4 (septic syndrome or life-threatening infection) 4, 5

Uncomplicated infections are superficial (cellulitis, simple abscesses, impetigo, furuncles) with low risk of life-threatening infection if treated appropriately, requiring only antibiotics or simple surgical drainage 4, 6
Complicated infections are deep tissue infections (necrotizing infections, infected ulcers, infected burns, major abscesses) with high risk of life-threatening infection, requiring significant surgical intervention with drainage and debridement 4, 6

Warning signs indicating severity include rapid progression of infection, violaceous bullae, disproportionate pain on physical examination, and rapid extension of erythema, suggesting necrotizing infection and requiring immediate surgical consultation 1, 2, 3, 7
Immunocompromised patients are automatically classified as severe due to the risk of unpredictable progression and higher mortality, including those with diabetes, HIV, or on immunosuppressive therapy 3
The IDSA recommends always evaluating independently: necrotizing or non-necrotizing character, anatomical extension, infection characteristics (purulent or non-purulent), and patient's clinical condition 4, 6, 7