skin and soft tissues infections

• related: Dermatology, mksap

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