DESCRIPTION

Infection associated with isolation of group A β-hemolytic streptococci (GABHS) from a normally sterile body site; includes three clinical syndromes:

• GABHS toxic shock syndrome (STSS)
• GABHS necrotizing fasciitis (NF)
  • Infection characterized by extensive local necrosis of skin and subcutaneous soft tissues
• Isolation of GABHS from normally sterile sites in patients who are not meeting criteria for STSS or NF (e.g., meningitis, osteomyelitis, septic arthritis, myositis, surgical wound infections) with or without bacteremia
• Diagnostic criteria for STSS:
  • (I) Isolation of GABHS
    • A: from a normally sterile site (e.g., blood, CSF, tissue, peritoneal fluid)
    • B: from a nonsterile site (e.g., throat, vagina, sputum, open surgical wound)
  • (II) Clinical signs of severity
    • A: hypotension
    • B: two or more of the following signs:
      • Renal impairment
      • Coagulopathy
      • Hepatic involvement
      • Acute respiratory distress syndrome
      • A generalized erythematous macular rash that may desquamate
    • C: soft tissue necrosis, including NF or myositis, or gangrene
• A definite case fulfills criteria IA and II (A and B). A probable case fulfills criteria IB and II (A and B) and no other identifiable cause.

EPIDEMIOLOGY

• Most cases occur in winter and early spring.
• Case fatality rates in children range from 10% to 30% in published reports.
• The average annual incidence in industrialized countries ranges from 3 to 5 per 100,000 per year and 10 to 43 per 100,000 per year in developing countries.
• Annual incidence appears to be increasing, possibly due to a change in prevalent emm types, although emm1 is still the most commonly identified type.
• Incidence is highest in infants and the elderly.

ETIOLOGY

Streptococcus pyogenes is the only species of β-hemolytic streptococci to be associated with invasive infections.

RISK FACTORS

• Risk factors for invasive GABHS infections include injuries resulting in bruising or muscle strain, surgical procedures, viral infections such as varicella, and use of nonsteroidal anti-inflammatory drugs (NSAIDs).
• High-risk groups include patients with diabetes mellitus, chronic cardiac or pulmonary disease, HIV infection or AIDS, and those with a history of IV drug use.
• Environmental factors such as overcrowding may potentiate cluster outbreaks.

GENERAL PREVENTION

• Routine immunization against varicella
• Isolation of hospitalized patients
• In addition to standard precautions, droplet precautions for children with pneumonia
• Contact precautions should be used for at least 24 hours after the start of antimicrobial therapy in children with extensive or draining cutaneous infections.
• There are several multivalent M protein–based vaccines in development that have progressed through early-stage human trials.

PATHOPHYSIOLOGY

• The pathogenic mechanism has not been fully defined; however, an association with streptococcal pyrogenic exotoxins (SPEs) has been suggested.
• SPEs A, B, and C (responsible for rash of scarlet fever) along with streptococcal exotoxins, mitogen factor, and superantigen stimulate activation of T lymphocytes and macrophages to produce large quantities of cytokines resulting in shock and tissue damage.