Strep Infection: Invasive Group A β-Hemolytic Streptococcus
Basics
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 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
- (I) Isolation of GABHS
- 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.
- Diagnostic criteria for STSS:
EPIDEMIOLOGY
- Overall mortality rates for invasive GABHS infections are lower in children (3.6–8.3%) than in adults (30–80%).
- Most cases occur in winter and early spring.
INCIDENCE
- The average annual incidence in the United States is approximately 3.5 cases per 100,000 persons.
- Incidence is highest in infants and the elderly.
- 85% of cases are sporadic, 10% hospital-acquired, 4% in chronic care facilities, 1% in cases with a close index contact.
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 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.
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.
- Several GABHS vaccine candidates are in varying stages of development. A 26-valent recombinant M protein vaccine is the only vaccine to have entered into clinical trials.
PATHOPHYSIOLOGY
- The pathogenic mechanism has not been fully defined; however, an association with streptococcal pyrogenic exotoxins (SPE) has been suggested.
- SPE 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.
ETIOLOGY
Streptococcus pyogenes is the only species of β-hemolytic streptococci to be associated with invasive infections.
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Citation
Cabana, Michael D., editor. "Strep Infection: Invasive Group a β-Hemolytic Streptococcus." Select 5-Minute Pediatrics Topics, 7th ed., Wolters Kluwer Health, 2015. Medicine Central, im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14144/6/Strep_Infection:_Invasive_Group_A_β_Hemolytic_Streptococcus.
Strep Infection: Invasive Group A β-Hemolytic Streptococcus. In: Cabana MDM, ed. Select 5-Minute Pediatrics Topics. Wolters Kluwer Health; 2015. https://im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14144/6/Strep_Infection:_Invasive_Group_A_β_Hemolytic_Streptococcus. Accessed December 10, 2024.
Strep Infection: Invasive Group A β-Hemolytic Streptococcus. (2015). In Cabana, M. D. (Ed.), Select 5-Minute Pediatrics Topics (7th ed.). Wolters Kluwer Health. https://im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14144/6/Strep_Infection:_Invasive_Group_A_β_Hemolytic_Streptococcus
Strep Infection: Invasive Group a β-Hemolytic Streptococcus [Internet]. In: Cabana MDM, editors. Select 5-Minute Pediatrics Topics. Wolters Kluwer Health; 2015. [cited 2024 December 10]. Available from: https://im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14144/6/Strep_Infection:_Invasive_Group_A_β_Hemolytic_Streptococcus.
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