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41 Cards in this Set
- Front
- Back
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Endotoxin
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LPS; Lipid A: repsonsible for toxicoty, Poly O: Protective, antigenic, determinint of strain
Only Gram Negative Integral part of outer membrane Always on a chromosome Weakly antigenic (O side) Cannot be converted to toxoid Weakly neutralized by antibody Stable with stands high temp Effects similr regardless of bacrerial origin |
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Exotoxin
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Produced by both gram + and -
Extracellular, usually secreted Phage or plasmid encoded Highly antigenic Converttable to non-toxic toxoids Readlily neutralized by antibody Unstable cannot stand high temp Effects vary upon type |
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Type 3 cytotoxins
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Bacteria binds to cell and inserets tube to inject toxins
Proteins never see the environment cant make toxoids against it |
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How does Toxic Shock Syndrom Toxin (TSST) enter the body?
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Mucoasl infection through the vaginal tract
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Superantigens
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Bind to MHC class II and T Cell Receptors
Binding NOT antigen specific T-Cells stimulated to produce IL-2, TNF, Il-1, Il-6, INF-Gamma Results in toxic shock |
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Staphylococcus Aureus TSST-1
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Found in women who used High Absorbency Tampons
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Staphylococcus Enterotoxins
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Intoxication of contaminated food
Causes vomiting and diarrhea Resistant to heat and digestive enzymes |
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Streptpcpccus Pyogenes Pyrogenic Exotoxins
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Responsible for rash in scarlet fever
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Diptheria
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Controlled by low iron levels
Acts primarily on throat |
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Cholera
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Increases cAMP levels which increase ion secretion and water leading to watery diarrhea
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Tetanus, Tetani
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Neurotoxin
Reaches CNS through motor nerves Causes spastic paralysis (lockjaw; arching of back) |
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How does virulence transfer between bacteria?
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By way of horizontal gene transfer mechanisms
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Endogeneous
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Normal flora get somewhere sterile
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Exogeneous
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Contact from food born, respiratory, sexual, vector, zoonoses
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Congenital
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Passed from mother to fetus
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Colonization
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First stage of microbial infection
Establishment of the pathogen at its point of entry |
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Receptor mediated binding of the bacteria
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Requires:
Adhesion, most commmon example is with the pili Receptor, specific carb or peptide that resides on surface of the host cell |
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Non-specific Binding
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Bind to host by secrition of viscous substances(biofilm, slime layer)
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Invasion
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Penetation of host cells and tissue
Mediated by INVASION by phagocytosis Gives advantage by supplying bacterium with nutrients from host |
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Dissemination
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Entrance of a bacterium into the blood stream
Example of a invasion by a bacteria |
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What do all bacteria require for growth
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Iron
Acquistion by eithier Siderophores or iron binding outer membrance proteins |
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Siderophores
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Iron binding chemicals that compete for iron bound to tansferin, Hb, or lactoferin
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Exotoxins
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Secreted by both
Can be easily converted to toxoid Three types: Local, systemic, superantigens (incude uncontrolled T cell cytokine release) |
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O polysaccharide
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Major antigenic determinant; antibody binding site
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Endotoxin
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Gram (-)
Cannnot be converted to toxoid No plasmid encoded Outer membrane Stable to boiling Clinical manifestation; shock and fever |
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Immunopathogenesis
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Damaged caused by the IS
Ex: Gram-bacterial sepsis, and Tuberculosis |
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How can bacterial avoid immune repsponses?
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Avoid contact
Inhibition of phagocytic engulfment by capsules Coat with IgA antibodies or inactivate C5A or C3A Bind antibody inappropriately by binding Fc of Ab Intracellular residence |
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What is one of the most important virulence factors?
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Encapsulation
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Enterotoxins
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Special exotoxins in the gut
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LPS
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Lipid A causes toxicity
CD14 interacts with TLR 4 Leads to activation of TNF and IL-1 Causes hypotention and shock |
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Disseminated Intravascular Coagulation (DIC)
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Activation of Factor XII (hageman factor) and causes occlusion of small vessels
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Classification of Exotoxins
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A-B subunit
B- Binding subunit mediates adherence of toxin complex to host cell and aids in transplocation of A A- Active subunit possesses the toxic activity; mediates host cell damage |
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Diphtheria toxin
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Catalyzes ADP ribosylation of EF2
Acts primarily on throat Encoded on a prophage Maximal effects under LOW IRON levels |
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Cholera Toxin
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Increase adenylate cyclase
Increasing cAMP levels Increased secretion of ions and water leads to DIARRHEA |
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Petussis Toxin
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Similar effect on Adenylate Cyclase but through Gi G protein receptor
Increases respiratory secretion Whooping cough |
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Shiga Toxin
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EHEC produces this toxin
Results in bloody diareha Deadenylates 28S rRNA blocking pretein synthesis |
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Bordetella Adenylate Cyclase Toxin
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Increased cAMP
Forms pores 2 toxins that interfere with phagocytosis |
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Clostridium Difficile Cytotoxins A and B
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Part of some peoples normal gut flora which can overgrow forming a enterotoxin
calls in PMNs leading to diarrhea |
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Alpha Toxin of Staphylococcus Aureus
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Toxic to RBC
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Streptococcus Pneumonia
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Toxic to ciliary action of pulmonary cells
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Clostridium Perfringes Alpha Toxin
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Causes detruction of all types of cells (RBC, WBC, platlets,muscle, endothelium, etc.)
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