lecture 7 exotoxins and leaving the host

-large porins; they insert raft of target cell membrane and forms large pores an example is enteroxin and enditheliotoxin known as epsilon toxin
-RTX (repeats in toxin porins)
produced by gram -ve and usually function porins
predominantly leukotoxin (WHC destructive) or haemolysins (RBC destructive)
@ low con. they increase intracellular ca, cell apoptosis, degranulation and @ high conc. cause cell lysis.
Leuotoxin of M. haemolytic causes feedlot pneumonia in cattle
-Enzymatically active toxin, 1 example is the alpha toxin of C. perfringens which causes gas gangrene which has an alpha toxin with phospholipase activity

they enter the cytoplasm of cells and disrupt cellular activities

• AB toxins

• using a molecular injector

AB toxins
an example of this is is neurotoxin; they effect they central and peripheral nervous system. For botulism, when its ingests it enters the intestinal tract and circulates in the lymphatics and bloodstream to the muscle. @ muscle proteins bind to the presynaptic membrane on motor end plate and it’s taken up by the axon. It the cleaves (splits) vesicles associated membrane proteins and realising the acetylcholine into synaptic junction, thus the muscle can’t contract
-using a molecular injector; some bacteria use type 3 secretion system to inject toxins into the cell. An example is salmonella species where it uses an injector to stimuli endocytosis of itself. Enteropathogenic; E. coli uses an injector to inject initimin into cell which causes the cell membrane actin polymerisation and it will attach more secure to the intestinal epithelium

-it can reduce O2 levels in H2O and prevent sunlight penetrating this is for algae blooms in fresh water
-when one of the exotoxins produced by the algae is ingested by animals or people they get clinical signs of liver disease for dogs this includes vomiting and diarrhoea for people they also get skin rashes and blistering lips, its also a tumour promoter
-neurotoxins cause respiratory paralysis
-usually present in highly populated areas
-control
good H2O management which reduces growth
-treatment of sewage and stormwater run offs
-stay away from slimy, scumming disgusting water
-fence off farm ponds, creek or other water sources
prevent fertiliser or shit going into water ways

intracellular active toxins
AB toxins
-enterotoxin;
killing cells; stops intracellular protein manufacture by shigatoxin of enterohaemorrhagic E. coli
once the strain of E. coli stick to the brush border of the intestine, they produce shigatoxin which enters the cell via receptor mediated endocytosis and is transported to the ribosome on the endoplasmic reticulum. There is cleaves (cuts) adenosine molecule from the ribosome stoping aminoacyl-tRNA binding and thus the ignition of protein manufacture resulting in cell death

-Anthrax toxin; killer of macrophages and other cells
it produces an AB toxin, its ag and goes into the membrane, activated and forms hetamper, which is then phagocytosed. All the different toxins enter the cell, the lethal factor (toxin) snips off the mitogen activated protein kinases leading to apoptosis and Oedema factor (toxin) increases cAMP in cell affecting water homeostasis (water leaves)

-DERMONECROTOXIN: A MITOGEN; it induces cell mitosis, enters the cell via receptor mediated endocytosis where is effect the production of G proteins and leads to decreased apoptosis and increase growth and causes the death of oestoblasts