Cellulitis

Definitions

  • 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
  • Impetigo (see Impetigo): infection of superficial layers of the epidermis
  • Necrotizing Fasciitis (see Necrotizing Fasciitis): deep-seated infection of subcutaneous tissue (involving fascia and fat), which may spare the skin
  • 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

SKIN INFECTIONS


Predisposing Factors

Local Factors

  • Skin Barrier Disruption: penetrating wound, IV drug abuse, etc
  • Skin Inflammation: eczema, radiation therapy, etc
  • Pre-Existing Skin Infection: impetigo, tinea pedis, etc
  • Edema: venous insufficiency, etc

Systemic Disease


Etiology


Diagnosis

Blood Cultures

  • Sensitivity/Specificity: positive in <5% of cases
  • Indications for Blood Cultures
    • Systemic Toxicity
    • Extensive Skin Involvement
    • Recurrent/Persistent Infection
    • Specific Host Factors: lymphedema, malignancy, neutropenia, immunosuppression/immunodeficiency, splenectomy, diabetes
    • Specific Exposures: animal bite, water-associated injury

Culture of Pus

  • Sensitivity/Specificity
    • Cultures of swabs from intact skin are rarely useful
    • Cultures of swabs from toe web intertrigo due to tinea pedis may be useful to identify pathogenic organisms in lower extremity cellulitis
  • Indications for Cultures of Pus
    • Extensive Skin Involvement
    • Recurrent/Persistent Infection
    • Specific Exposures: animal bite, water-associated injury
    • Specific Host Factors: lymphedema, malignancy, neutropenia, immunosuppression/immunodeficiency, splenectomy, diabetes
    • Systemic Toxicity

Skin Punch Biopsy

  • Sensitivity/Specificity: only positive in 20-30% of cases
    • Suggests that relatively small numbers of bacteria may result in significant inflammation with most of the observed findings being due to the host inflammatory response
    • Usually not performed

Needle Aspiration of Bullae

  • Sensitivity/Specificity: positive in <5-40% of cases
    • Suggests that relatively small numbers of bacteria may result in significant inflammation with most of the observed findings being due to the host inflammatory response
  • Indications for Needle Aspiration of Bullae
    • Extensive Skin Involvement
    • Recurrent/Persistent Infection
    • Specific Exposures: animal bite, water-associated injury
    • Specific Host Factors: lymphedema, malignancy, neutropenia, immunosuppression/immunodeficiency, splenectomy, diabetes
    • Systemic Toxicity

X-Ray/CT/MRI

  • May be useful in some cases to exclude skin abscess or to distinguish cellulitis/erysipelas from osteomyelitis or gas gangrene
    • However, radiologic exams cannot reliably differentiate cellulitis from necrotizing fasciitis or gas gangrene and these should not delay surgical intervention if necrotizing fasciitis or gas gangrene are suspected

Clinical Manifestations

  • Skin Erythema, Warmth, and Edema without an Underlying Suppurative Focus
    • Most Common Site of Involvement: lower extremities
    • Pain may occur
    • Associated Lesions: variably occur
      • Vesicles/Bullae (see Vesicular-Bullous Skin Lesions, [[Vesicular-Bullous Skin Lesions]])
      • Ecchymoses
      • Petechiae (see Petechiae, [[Petechiae]])
      • “Peau D’Orange” (Orange Peel) Appearance: due to edema surrounding hair follicles with dimpling of the skin
  • Lymphangitis/Inflammation of Regional Lymph Nodes (see Lymphadenopathy, [[Lymphadenopathy]]): may occur

Treatment

Antibiotics

  • Ceftaroline (Teflaro, Zinfloro) (see Ceftaroline, [[Ceftaroline]])
  • Tigecycline (Tygacil) (see Tigecycline, [[Tigecycline]])

References

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