Tsst and Hypotension

Topics: Streptococcus pyogenes, Immune system, Streptococcus Pages: 3 (413 words) Published: February 16, 2013
Pathogenesis

Hypotension and Toxic Shock Syndrome (TSS)
* Toxic shock syndrome (TSS) is a bacterial toxin
* Causative pathogens include certain strains of:
* Sta. Aureus (TSST-1)
* Str. Pyrogenes (Str. Pyogenes exotoxins)
Str. Pyogenes – Cause of Group A Streptococci
* Spherical
* Gram-positive bacterium
* Displays streptococcal Group A Ag on cell wall
* releases Str. Pyrogenic exotoxins A
Role of Superantigens in Staphylococcal and Streptococcal Toxic Shock Syndrome * Toxic shock syndrome (TSS) is a rapid-onset illness causing: * fever
* hypotension
* rash
* vomiting
* diarrhea
* eventual multiple organ failure 

* TSS is caused by the nonspecific stimulation of T lymphocytes by superantigens belong to pyrogenic toxins family.

* Superantigen:
* Can be viral or bacterial protein
* Bacterial proteins cross link variable B domain of T-cell receptor to a chain class II MHC molecules. * Crosslink provides signals that induces T-cell activation * Binds outside of the antigens-binding cleft (no APC)

* Activates any clones of T-cells expressing VB sequence
* Causes polyclonal T-cell activation
* Activated T-cells secrete large amount cytokines, IFN-γ * Excess IFN-γ activates macrophages
* Activated macrophages overproduce proinflammatory cytokines such as cytokines (IL-1, IL-6,TNF-α) * Excess amounts of cytokines induce systemic toxicity and multisystem failure

* Str. Pyogenes causes three types of disease:
* Pyogenic (pharyngitis and cellutis)
* Toxigenic (scarlet fever and streptococcal TSS)
* Immunologic (rheumatic fever and AGN)
* Cause toxic shock syndrome (TSS) by stimulating the release of large amounts of IL-1, IL-2 and TNF * Similar mode of action as Sta. Aureus (TSST-1)
* Recognizable site of pyogenic inflammation
* Cultures often positive
Clinical Findings: Hypotension...

References: Forni AL, Kaplan EL, Schlievert PM, Roberts RB. (1995). Clinical and microbiological characteristics of severe group A streptococcus infections and streptococcal toxic shock syndrome. Clinical Infectious Diseases 21: 333–34.
Levinson, W. (2010). Review of medical microbiology and immunology. 3rd ed. New York: McGraw Hill Companies, Inc.
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