Streptococcal Disease

Basics

Increase in frequency of aggressive streptococcal necrotizing skin infection noted in 1980s and dubbed “flesh-eating bacteria”
Affects otherwise healthy patients aged 20–50 yr who did not have underlying predisposing diseases
Rapid progression of shock and multiorgan dysfunction, with death occurring within 1–2 d
Incidence is 3–4 per 100,000 in industrialized countries
Invasive infections caused by group A Streptococcus (GAS) include:
- Necrotizing fasciitis (NF):
  - Progressive, rapidly spreading soft tissue infection located within the deep fascia and subcutaneous fat
- Streptococcal toxic shock syndrome (STSS):
  - May occur in patients with GAS-associated NF
  - Portals of entry for streptococci include vagina, pharynx, mucosa, and skin
  - Unknown cause in 50% of cases
- “Other” invasive disease defined as isolation of GAS from a normally sterile body site (i.e., sepsis, bacteremic pneumonia, septic arthritis, etc.)
Occurs sporadically, with occasional outbreaks in long-term care facilities and hospitals
Rate of invasive GAS disease 6 times the annual incidence of meningococcal disease

STSS Case Definition

NF:
- GAS is causative in 10% of cases. Blunt trauma is risk factor
- Mixed anaerobic and aerobic organisms are found in 70% of cases
- Staphylococcus aureus, Clostridium species, and other enteric organisms
STSS:
- Occurs when susceptible host is infected with virulent strain
- M protein types 1, 3, and 28 are most common
- Pyrogenic exotoxins (e.g., A, B, and C) produce fever and shock via activation of tumor necrosis factor and interleukins
- Nonsteroidal anti-inflammatory drugs appear to mask or predispose patients
- Risk factors:
  - Age <10 or >60 yr
  - Cancer
  - Renal failure
  - Leukemia
  - Severe burns
  - Corticosteroids

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