Bacterial Toxins Flashcards
What is an Endotoxin?
heat stable component of gram negative bacteria, not secreted, lipid A portion binds TLR4 and cause immune response
What is an exotoxin?
heat labile protein, component of gram positive bacteria and is secreted into the environment, some of the most toxic substances known to man
What are A-B toxins?
A sub-type of exotoxin that has an active site (a) and a binding site (B)
What is the general MOA for A-B toxins
causes cell death by interfering with protein synthesis
What organism does the diphtheriae toxin come from and what is it’s structure
comes from corynebacterium diphtheriae (gram positive), 3 domains, receptor binding, transmembrane and catalytic domain
What is the diphtheria toxin MOA?
Inactivates elongation factor two, which allows for the translocation of the ribosome during protein synthesis
How is diphtheria transmitted, general signs of infection, how long it lasts and how it is treated?
transmitted orally, pseudomembrane in back of throat due to cells dying, lasts days to weeks and treated with antibiotics
What organism does the shiga toxin come from and what is it’s structure?
STEC E.coli strains-most commonly O157:H7 strain. A subunit and a pentamer B subunit
What is the shiga toxin MOA
Bacteria colonizes the intestines, toxin binds glycosphingolipid receptor, transported to ER from golgi, A subunit cleaved into two and inactivates ribosomes
How is shiga toxin obtained normally, what are its symptoms, what is its onset of symptoms and how long does the infection last?
Eating ground beef, unpasteurized milk or fresh produce, diarrhea, cramping and sometimes vomiting, onset 2-3 days, usually resolves in a week
Why is the onset of the shiga toxin 2-3 days?
The bactiera needs time to colonize the intestine
Who are the most at risk for infection of Shiga toxin and what harmful symptoms can it cause?
Young children and elderly, kidney failure and death
What organism produces the botulism toxin and what is the toxins structure?
Clostridium botulinum (gram positive), 3 domains-catalytic, translocation and binding domain
What is botulism’s MOA?
binds presynaptic neuron, receptor mediated endocytosis, proteolysis of SNARE and SNAP proteins and halted acetylcholine release
What is the onset for botulism and it’s LD50?
onset 12hr-3d, LD50: 1-3ng/kg
What are the symptoms of botulism posioning?
descending paralysis, nausea, dry mouth, difficulty swallowing, blurred vision, droopy eyelids, eventual death by respiratory paralysis
What are the other forms of botulism and how are they acquired?
Infant botulism-spore found in honey
Wound-spores entire wound and germinate in the wound (deadly)
Avian botulism-eating infected food source
What is the treatment for infant botulism and why can adults eat honey with no issue?
Botulism Immune Globulin Intravenous- neutralizes circulating toxin, babys gut isn’t as acidic so spores can live
How does one treat botulism and diagnose it?
anti-toxin for unbound toxin, respiratory ventilator so person doesn’t die, mouse bioassy and symptom assessment for diagnosis
What organism produces the tetanus toxin and what is its structure?
Produced by clostridium tetani (gram positive) and it is a A-B multidomain protein
What is tetanus’s MOA?
Cleaves synaptobrevin and syntaxin, prevents release of GABA and glycine
How is tetanus acquired, what is its onset and symptoms?
enters through wounds, descending paralysis often beginning with lockjaw and eventual death from suffocation, onset 3d-3w
How is tetanus treated and how long does it take to recover from if you live?
control spasms, antibiotics for to prevent further toxin production and respirator
What is a toxoid vaccine?
an inactivated toxin done by heat or formaldehyde
What is ADP ribosylation?
post translational modifications of proteins that involves the transfer of one or more molecules of ADP-ribose from NAD+
What are some biological functions of ADP ribosylation?
DNA damage repair, cell proliferation, cell differentiation, stress, metabolism and immune function
What organism produces the Iota toxin and what is the structure of the toxin?
produced by clostridium perfringens (gram positive), composed of Ia and Ib
What is the Iota toxin’s MOA?
ADP-ribosylation of G-actin which inhibits the polymerization of F actin
What are the other classes of toxins produced by C. perfringens?
Type C and Type D
What are the two subclasses of Type C toxins and their MOA?
Alpha toxin: A phospholipase that contributes to tissue damge
Beta toxin: pore forming toxin that causes severe necrotizing enteritis (most commonly in livestock) (defining)
What are the two subclasses of Type D toxins and their MOA
Alpha: involved in tissue damage
Epsilon: pore forming toxin in endothelium especially in brain and kidneys (defining)
What are the symptoms from Iota toxin in humans?
fever, dehydration, food poisoning symptoms, necrosis of small intestine (necrotic enteritis)
What are the symptoms produced by the iota toxin in animals?
ataxia, convulsions, necrotic enteritis, pulpy kidney disease, sudden death
What are the treatments for Iota toxin?
penicillin, antitoxin and supportive care
What organism produces the cholera toxin and what is its structure?
produced by vibrio cholerae (gram negative) and has A and B subunit
What is cholera’s MOA?
ADP-ribosylation of G protein, activation of AC which leads to increased cyclic AMP, rapid efflux through CFTR channel, decreased sodium ion, electrolyte imbalance-metabolic acidosis and death
How is cholera transmitted, identified and treated?
ingestion of water with fecal matter, identified in feces and IV treatment with electrolyte replacement and antibiotics
