Pathogenic Mechanisms II
what are the clinical signs of low concentration of lipid A
fever, vasodilation, increased antibody synthesis, inflammation
what is the effect of membrane damaging toxins
most cytolytic/cytotoxic
what are the classifcations of membrane damaging toxins
phospholipases and pore forming toxins
what are the different actions of exotoxins
toxins that act extracellularly, toxins that act at the cell surface, toxins that act intracellularly
what are endotoxins
toxins that can't be separated from live bacteria, lipopolysaccharide
What does botulinum toxin do?
blocks release of ACh at neuromuscular junction causing flaccid paralysis
how do AB toxins enter the cell
1. B binds host cell and enters either through endocytosis or A translocates through B 2. A is free in the cytoplasm 3. A has its toxic effect
what are the steps of gram negative septic shock
1. bacteria lyse 2. Free LPS 3. LPS binds LPS binding proteins 4. LPS complex binds CD14 on macrophages 5. Macrophages releases pro-inflammatory cytokines 6. prostaglandins, leukotrienes, activation of complement cascade, activation of coagulation cascade 7. acute respiratory distress syndrome, disseminated intravascular coagulatation, multi-system organ failure
what happens during contact dependent secretion
1. bacteria senses theyre in contact with host cell 2. bacteria starts secreting proteins that form a controlled pore (injectosome) 3. bacterial start secreting through injectosome
What is the toxic portion of LPS?
Lipid A
what is the B port of AB toxins
binds the toxin to host cell surface
how do exotoxins stimulate cytokine production
activate 5-20% of T cells by binding to a conserved region on the T cell receptor and MHC II which activates the T cell
what is cytotonic mean
alters cell activity but does not kill them
what are AB toxins
bifunctional with separate domains or subunits
what is the function of phospholipases
cleave phospholipids in cell membrane
how do exotoxins act at the cell surface
damage membranes
what are the clinical signs of high concentration of lipid A
endotoxic shock
what are spreading factors function
enhanne disperal of microorganisms in tissues by breaking down extracellular matrix or debris in necrotic tissue
what type of bacteria produces endotoxins
gram negative bacteria
how do exotoxins act intracellular
inhibit protein synthesis, modify intracellular signaling, modify intracellular trafficking, alter cytoskeleton
what is the function of pore forming toxins
inserts pore which affects concentrations and either activates immune system or kill cell when enough pores are inserted
how is activating T cells beneficial to the microorganism
its not targeting the pathogen, just the superantigen which exhausts immune system
what does tetanus toxin do
prevents release of inhibitory neurotransmitters in spinal cord causing rigid paralysis
What are toxins?
product of microorganism that harms susceptible animals by altering cellular struture and/or function
what exotoxins stimulate cytokine production
pyrogenic exotoxins and are superantigens
how do exotoxins act extracellularly
stimulate cytokine production and spreading factors
what are the clostridium toxins that alter neurotransmitter release
tetanus and botulin
what is the A part of AB toxins
the active part of the toxins
why are antibodies not effective against contact-dependent secretion
the proteins are always intracellular
what is essential for pathogenesis of dimorphic fungi
their availability to convert from one form to another
how do extoxins alter cytoskeleton
they are cytotonic and disrupt or activation or actin polymerization. can act on actin directly or indirectly through Rho family of small GTP binding proteins
how do exotoxins modify intracellular signaling
they are cytotonic by increasing adenylate cyclase or guanylate cyclase and activation of host cyclases to activate ion transport. some bacteria make their own cyclases
how do exotoxins modify intracellular trafficking
they are cytotonic, inhibit neurotransmitter release (clostridium toxins) because they are endopeptidases which inactivate proteins required for neuroexocytosis
how do exotoxins inhibit protein synthesis
they are cytotoxic by modifying ribosomal proteins or damage rRNA
what is not a reason that bacteria enter cells
to avoid hydrogen peroxides
what exotoxins
toxins found outside of cell, protein