Staphylococcal Disease

Staphylococcal Disease

 

Staphylococcus aureus is a gram-positive cocci that causes superficial skin infections such as folliculitis, impetigo, and cellulitis and as well as deep-seated infections such as endocarditis, osteomyelitis and tissue abscesses.

Epidemiology

  • Incidence
    • Cellulitis accounts for 2% of outpatient office visits
    • Deep-seated infections are uncommon
  • Transmission
    • Portal of entry for superficial infections may be a surface abrasion but is frequently unknown
    • For deep infections, portal of entry may be surgery or indwelling catheter

Organism

  • Gram positive coccus
  • May acquire multi-resistance and be called methicillin resistant staphylococcus (MRSA)

Risk Factors

  • Immune deficiency
  • Diabetes mellitus
  • Hospitalization
    • Indwelling catheters
  • Intravenous drug use (IVDU)
  • Primary viral exanthem (e.g., varicella zoster)
  • Alcohol abuse
  • Local trauma

Clinical Presentation

  • Superficial infections
    • Folliculitis
    • Impetigo
    • Cellulitis
      • More commonly caused by beta-hemolytic streptococcus
      • Erythema and warmth, swelling and tenderness of affected area
    • Abscess
      • >50% are caused by staphylococcus
      • Includes furuncles, carbuncles
    • Necrotizing fasciitis
      • Type 1 is frequently caused by staphylococcus
  • Deep infections
    • Endocarditis – usually associated with prosthetic valves, indwelling catheters, or IVDU
    • Osteomyelitis – frequently associated with underlying immune deficiency
    • Deep tissue and muscle abscesses

Diagnosis

  • Superficial disease diagnosed by culture of wound or affected area
  • Diagnosis of deep-seated infections caused by S. aureus is best made by cultivating the organism from appropriate clinical specimens
  • Bacteremia associated with deep-seated staphylococcal infection presents a puzzling picture to both the clinician and laboratory technician, since the focus of infection may not be readily apparent
  • Prolonged exposure to staphylococci during deep-seated infection can result in elevated antibodies to staphylococcal ribitol teichoic acid
    • High antibody levels (1:2 or greater) against staphylococcal ribitol teichoic acid in patients with staphylococcal bacteremia indicates staphylococcal endocarditis or complicated staphylococcal bacteremia

Treatment

  • Superficial – frequently cured with antibiotic therapy and abscess drainage
  • Deep – involves tissue debridement and abscess drainage

See Also