skin and soft tissues infections

Skin and Soft Tissues

Introductions

Types of skin infections:

  • Purulent: usually staph
    • abscess
    • furuncles
    • carbuncles
  • Nonpurulent: usually beta-hemolytic strep
    • erysipelas
    • cellulitis
    • necrotizing skin infections

Erysipelas and Cellulitis

  • Erysipelas: epidermis, upper dermis, superficial lymphatics
  • Cellulitis: deeper dermis, subcutaneous fat tissues

Differential diagnosis:

  • contact or stasis dermatitis
  • lymphadema
  • erythema nodosum
  • DVT
  • thrombophlebitis
  • lipodermatosclerosis
  • erythromelalgia
  • hypersensitivity reactions

Diagnosis

  • Blood cultures: positive 5%. Not routinely used
  • Skin aspirate/biopsy: consider
  • Imaging: not helpful but can use to exclude necrotizing infection

Treatment

  • Surgical debridement: necrotizing infection, bullae, desquamation
  • Duration: 5 days and extend as necessary until improvement
  • Ppx: Consider penicillin or erythromycin for patients with >3 episodes annually

  • Stasis dermatitis
    • Stasis dermatitis is caused by fluid buildup due to varicose veins, circulation issues, or heart disease.
    • Skin discoloration of the ankles or shins, itching, thickened skin, and open sores (ulcers) are symptoms.
    • Treatments may include compression stockings and prescription creams as well as treating the underlying condition.

Necrotizing Fasciitis

  • subdermal compartments: fascia, muscle
  • usually spreads along superficial fascia
  • usually occur with previous skin trauma/infection, extremities more often
  • risk factors: DM, IVDU, malignancy, liver disease, immunocompromised
    • liver disease: V. vulnificus especially
    • DM: NF of perineum, Fournier gangrene
  • bacteria: Streptococcus pyogenes, Staphylococcus aureus, Streptococcus agalactiae, Aeromonas hydrophila, Vibrio vulnificus, and Clostridium perfringens.
  • LRINEC score for risk indicator

Bullous cellulitis characteristic of Vibrio vulnificus infection is shown in a patient with cirrhosis; cutaneous necrosis is also evident, most likely associated with disseminated intravascular coagulation.

  • Sx:
    • initially resembles cellulitis
    • rapid progression with edema, severe pain, bullous lesion, skin necrosis, crepitus, anesthesia
    • SIRS
    • characteristics: "woody" induration with palpation
  • Labs: nonspecific
  • Imaging:
    • gas in soft tissues
    • MRI > xray/CT
  • Treatment
    • empiric: aerobic and anaerobic organisms (including MRSA) and consists of vancomycin, daptomycin, or linezolid plus piperacillin-tazobactam, a carbapenem, ceftriaxone plus metronidazole, or a fluoroquinolone plus metronidazole. Some experts also recommend adding empiric clindamycin because of its suppression of toxin production by staphylococci and streptococci.
    • Antimicrobial discontinuation can be considered when the patient is afebrile and clinically stable, and surgical debridement is no longer required.

Purulent Skin Infections

  • Abscess: pus collection in dermis, subcutaneous fat
  • Furuncles: boils. Hair follicle associated abscess into dermis/subcutaneous tissues
  • Carbuncle: extension subcutaneously with several furuncles
  • Treatment
    • I&D
    • Gram stain and culture with drainage
    • MRSA: decolonization with topical intranasal mupirocin and chlorhexidine washes