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Group A Streptococcus invasive infections: a review
1Department of Microbiology and Infectious Diseases, Hôpital Maisonneuve-Rosemont, Université de Montréal, Que.
Abstract:
The incidence of group A Streptococcus (GAS) invasive infections has been increasing worldwide, and there is no obvious explanation for this phenomenon. In 1993, a working group on severe GAS infections was established to define accurately what constitutes an invasive infection. Three types of infection are particularly feared: necrotizing fasciitis, myositis and a newly defined entity, named streptococcal toxic shock syndrome (STSS) because of a certain analogy with its staphylococcal counterpart. GAS produces many toxins responsible for its clinical manifestations. Some of them, labelled streptococcal pyrogenic exotoxins, have been characterized as superantigens. These proteins play a key role in initiating the immune response to GAS and are mostly responsible for the precipitous course of invasive infections. Death rates are high in streptococcal invasive infections, ranging from about 20% for necrotizing fasciitis to almost 100% for myositis. Therapy consists mainly of high doses of antibiotic combinations, aggressive surgery, and intravenous administration of immunoglobulins for STSS.
Insights
Group A Streptococcus (GAS) invasive infections are rising globally. Researchers defined severe GAS infections like necrotizing fasciitis, myositis, and streptococcal toxic shock syndrome (STSS).
Area of Science:
- Infectious Diseases
- Microbiology
- Immunology
Background:
- Global incidence of invasive group A Streptococcus (GAS) infections is increasing without clear cause.
- A working group defined severe GAS infections in 1993, identifying key feared entities.
- Severe GAS infections include necrotizing fasciitis, myositis, and streptococcal toxic shock syndrome (STSS).
Purpose of the Study:
- To define severe group A Streptococcus (GAS) infections.
- To characterize the toxins and superantigens produced by GAS.
- To understand the immune response and clinical manifestations of invasive GAS infections.
Main Methods:
- Defining criteria for severe GAS infections.
- Characterizing GAS toxins, specifically streptococcal pyrogenic exotoxins (superantigens).
- Reviewing clinical manifestations and outcomes of invasive GAS infections.
Main Results:
- Identification and definition of necrotizing fasciitis, myositis, and STSS.
- Characterization of streptococcal pyrogenic exotoxins as superantigens crucial to GAS pathogenesis.
- High mortality rates associated with invasive GAS infections (20% for necrotizing fasciitis to nearly 100% for myositis).
Conclusions:
- Invasive group A Streptococcus (GAS) infections, including STSS, are a significant and increasing global health threat.
- GAS superantigens play a critical role in the rapid progression and severity of these infections.
- Effective treatment requires a multi-modal approach including antibiotics, surgery, and immunoglobulins for STSS.