Lecture 4-Toxins-Staphylococcus 2010

Lecture 4-Toxins-Staphylococcus 2010 - Lectures 4 Toxins...

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Lectures 4 Toxins Staphylococcus
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Review: Cell shape and arrangement of bacteria
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Review: Cell shape and arrangement of bacteria Conclusion: Gram-stain is also very important to determine cell shape and arrangement of bacteria (diagnostic tool!) Therefore need to DILUTE bacteria for gram staining!!
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Review: Structure Chapter 3
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Review: gram pos. vs. neg. Characteristic Gram-Positive Gram-Negative Outer membrane - + Cell wall Thicker Thinner LPS - + Teichoic acid Often present - Sporulation Some strains - Capsule Sometimes present Sometimes present Lysozyme Sensitive Resistant Antibacterial activity of penicillin More susceptible More resistant Exotoxin production Some strains Some strains
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TOXINS Bacterial products that either directly harm/destroy host cells (=Aggressin) or induce a harmful biological response (=Modulin) which then leads to tissue destruction
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Endo and Exotoxins Endotoxin (e.g. LPS) and other integral cell wall components -causes local effects Exotoxin, secreted proteins - Classification into three types according to their activity (not stringent/overlap between types) - cause systemic effects, without local presence of bacteria!
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Endotoxin and Endotoxin-like LPS only in gram neg. bacteria Gram positive bacteria have other cell wall components with endotoxin activity (PG, teichoic acid, lipoteichoic acid) All mediate very intense pro-inflammatory (pyrogenic) responses Interact with PRR (e.g. TLR-2 or TLR-4) on surface of immune cells
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Exotoxins (general) Type I (membrane acting) toxins Act from outside of cell to influence host cell signal transduction some are “super antigens” (Staphylococcus enterotoxins; Streptococcal pyrogenic exotoxins=Spes)
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What is a superantigen? Activation of T-cells via superantigens may result in T-cell death (immunosuppression) or T-cell activation leading to cytokine secretion, followed by very strong inflammatory response leading to tissue damage, organ failure, toxic shock.
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Exotoxins (general) Type II (membrane-damaging) toxins 1. Channel forming toxins ( α -toxin- St. aureus ) 2. Enzyme Toxins ( β -toxin- St. aureus )
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Exotoxins (general) Type III (intracellular) toxins 1. A-B Toxins: two chain molecules B-subunit mediates binding to target cell and internalization A-subunit inhibits intracellular target Toxin targets very well defined tissues/cells
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Lecture 4-Toxins-Staphylococcus 2010 - Lectures 4 Toxins...

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