Definitions of Skin/Soft Tissue Infections

• Impetigo (see Impetigo): infection of superficial layers of the epidermis
• Cellulitis (see Cellulitis): skin infection of deeper dermis and subcutaneous fat (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
• Erysipelas (see Erysipelas): skin infection of upper dermis and superficial lymphatics (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
• Furuncle (Boil) (see Skin Abscess): infection of hair follicle where purulent material extends through the dermis into the subcutaneous tissue, forming a small abscess
• Carbuncle (see Skin Abscess): coalescence of several inflamed follicles into a single inflammatory mass with purulent drainage from multiple follicles
• Skin Abscess (see Skin Abscess): collection of pus within dermis and deeper skin tissues
• Necrotizing Soft Tissue Infection (see Necrotizing Soft Tissue Infection): deep tissue infection involving the hypodermis (and contained structures)
  • All of These are Characterized by Fulminant Tissue Destruction, Systemic Toxicity (Tachycardia >120 Beats/min, Hypotension, Elevated Creatine Kinase, CRP >15 mg/dL, LRINEC Score >6, etc), and High Mortality Rates

Microbiology

• Staphylococcus Aureus (see Staphylococcus Aureus): most common etiology of impetigo
• β-Hemolytic Streptococcus: less common etiology of impetigo
  • Streptococcus Pyogenes (Group A) (see Streptococcus Pyogenes): most common Streptococcal etiology of impetigo
  • Streptococcus Dysgalactiae Subspecies Equisimilis (Group C/G) (see Group C+Group G Streptococcus)

Clinical Manifestations

Radiologic Presence of Soft Tissue Gas May Allow Clinical Differentiation of Necrotizing Soft Tissue Infections (NEJM, 2017) [MEDLINE]

Dermatologic Manifestations

• Bullous Impetigo (see Vesicular-Bullous Skin Lesions)

Other Manifestations

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References

• Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2014 Jul 15;59(2):e10-52. doi: 10.1093/cid/ciu444 [MEDLINE]