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Toxins Flashcards

1
Q

Three categories of toxins

A

Enzymes

Receptor proteins

Inappropriate immune responses

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2
Q

Exotoxins

A

Are secreted by bacteria and are not integral parts of the bacterial structure

  • can act locally or systematically

Ex: diphtheria, cholera, botulinum, shiga, anthrax etc.

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3
Q

Exotoxins

A

Membrane bound toxins that are on bacteria and are integral parts oft heir membrane

  • can act on the host cell structure
  • can act as super antigens
  • can hydrologic enzymes that splice host enzymes

Ex: LPS and pore forming proteins

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4
Q

Exotoxin subtypes/categories

A

B subunit: mediates adherence of the toxin to the host cell or aids in allow the toxin to enter the host cell

A subunit: actually produces the toxic affect

can either be synthesized together and then cleaved or separately pending on the bacteria

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5
Q

LPS

A

Gram negative bacteria endotoxins that is associated with the cell membrane

  • possesses a lipid A portion that induces fever and release of IL-1/TNF of macrophages (induce inflammation)
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6
Q

Bacillus anthracis

A

Gram positive,non motile, facultative anaerobic (but prefers aerobic), spore forming, rod

  • is the etiological agent of anthrax*

Produce their virulence factors via plasmid production

Possesses three proteins as the toxins

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7
Q

Bordetella pertussis

A

Gram negative aerobic coccobacillus

  • causative agent of whopping cough*

Possesses two main toxins

  • Pertussis toxin (PT)
  • hydrolysis cellar NAD+ = inactivates G proteins
  • protein vaccinated against*
  • Adenylate Cyclase toxin (ACT)
  • generates pores in red blood cells = hemolysis
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8
Q

Corynebacterium diphtheria

A

Gram positive rod

causative agent of diphtheria

Produces 1 major toxin (diphtheria toxin)
- inhibits peptide chain elongation factor (EF-2) = causes inhibition of ribosomes and cell death

  • causes new bacterial membrane formation in throat mucosa and leads to suffocation if not fixed*
  • high levels of inorganic iron limits growth rate*
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9
Q

Clostridium tetanus

A

Anaerobic gram positive rod

  • causative agent of tetanus*
  • contaminates open wounds

Possesses one major toxin (tetanospasmin)

  • binds to receptors on presynaptic membranes of motor neurons
  • ultimately degrades synaptobrevin which is required for docking of neurotransmitter vesicles on inhibitory presynaptic neurons = spastic paralysis and suffocation
  • requires immunization with tetanus toxoid*
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10
Q

Clostridium botulinum

A

Anaerobic gram-positive spore forming

causative agent of botulinum poisoning

MOST POTENT TOXIN = botulinum toxin

  • is heat liable
  • absorbed from the gut
  • toxin moves to target function similarly to tetanus except it functions differently

Functions to inhibit release of acetylcholine at synapse of presynaptic motor neurons.
- induces flaccid paralysis

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11
Q

Clostridium perfringens

A

Anaerobic gram positive spore-forming

Are introduced into wounds by contaminated soil of feces

Produces several different toxins but all lead to gas gangrene of the wound

  • spores produce gas via replication and digestion of carbohydrates in the host cells
  • Also limits blood flow due to the site causing necrosis/hypoxia
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12
Q

Toxins produced by clostridium perfringens

A

Alpha/beta/epsilon/iota/ enterotoxin

Necrotic B-like

Collagenases and DNAses

Alpha toxin (CPA)

  • lecithinase which damages cell membranes by splitting lecithin
  • main culprits of gas gangrene in adults *

CPB (gas gangrene in babies) and CPE (food poisoning)

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13
Q

Staph aureus

A

Gram positive non-motile cocci

Colonies are everywhere and have multiple infections

Produces 5 virulence factors

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14
Q

Virulence factors of staph aureus

A

Panton- valentine leukocidin (PVL)
- lysis human white blood cells

Alpha- hemolysis (alpha toxin)
- forms pores in all cells

Phenol-soluble modeling (PSMs)
- amphipathic proteins that lyse human cells

ACME and agr proteins
- controls expression of toxins

lysing cells cause release of iron which promotes invasiveness of infection and replication

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15
Q

Staphylococcal enterotoxin

A

Special type of staph aureus toxin that is absorbed by the gut
-when absorbed, stimulates vagus nerve receptors which induce vomiting

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16
Q

Streptococcus species

A

Gram positive cocci

Group A are the most dangerous

  • (beta) hemolytic and produce pyrogenic exotoxins
  • also produce streptococcal pyrogenic exotoxin B which cleaves antibodies

All produce streptolysin S/O which are pore forming

17
Q

What is the most potent toxin?

A

Botulinum

Diphtheria is lest potent but still very toxic

18
Q

Lipid A portion of endotoxins

A

Parts of the endotoxins that causes fever

- does this by release IL-1 and TNF from macrophages and induces physiologic effects associated w/ inflammation

19
Q

Bacillus anthracis virulence factors and toxins

A

Virulence factors = from plasmids

  • toxin production
  • capsule formation

Contains three toxins
Protective antigen (PA)
- binds to cell and permits entrance

  • Lethal factor (LF)
  • decreases MAPK which completely inhibits intracellular enzymes = hypoxia and necrosis
  • Edema Factor (EF)
  • Stimulates massive amounts of cAMP production within host cells = edema
  • protective antigen is target for vaccines*
20
Q

Bordetella pertussis toxins

A

Pertussis toxin (PT) = hydrolyzes cellular NAD and transfers the released ADP-ribose to deactivate G-proteins

Adenylate Cyclase Toxin (ACT) = Forms pores to lyse RBCs

PT is the toxin used for vaccines

21
Q

Corynebacterium diptheriae toxin

A

Encoded in a lysogenic temperate bacteriophage.

Toxin inhibits peptide chain elongation factor (EF-2) by attaching an adenosine diphosphate-ribosyl group
- B subunit allows entrance where as A subunit does the above toxic effect

  • toxin production is inversely related to iron availability*
22
Q

Clostridium tetani toxin

A

Tetanospasm

  • binds to receptors on presynaptic membranes of motor neurons and enters inhibitory cells
  • once in the inhibitory cells, degrades synaptobrevin, which is required for inhibitory cells to work

immunizations w/ small amounts of the tetanus toxoid

23
Q

Clostridium botulinum toxin

A

most potent toxin, heat labile and absorbed in the gut

  • Binds to receptor of presynaptic membranes of motor neurons and initiates proteolysis of target proteins in neurons (SNARE proteins)
  • heavy chain binds to the receptor
  • light chain actually does the cleaving of the SNARE proteins
  • ultimately inhibits release of acetylcholine at the synapses
24
Q

Clostridium perfringens toxin

A 
Alpha toxin (CPA) 
- main virulence factor called lecithinase which works to damage cell membranes by splitting lecithin to phosphorylcholine and diglyceride 
Beta toxin (CPB) 
- enterotoxemia primarily in neonatal patients

Enterotoxin (CPE)
- food poising causing agent

Also produces collagenases and DNAases

25
Q

Panton-valentine leukocidin (PVL)

A

Is a virulence factos of staph aureus Lysis of human white blood cells

26
Q

Alpha-hemolysis (alpha-toxin) and hemolysis A

A

Virulence factor and toxin of staphylococcus aureus respectively

Both Form pores in cells leading to cell lysis by using H1a subunits to generate pores in the membrane

27
Q

Phenol-soluble modulins (PSMs)

A

Virulence factor for staphylococcus aureus

Lyse human neutrophils and RBCs by attaching to the cytoplasmic membrane and leading to membrane disintegration

28
Q

Staphylococcus aureus toxins

A

All function to damage the cell membranes of host via two ways

  • degrade inter-cellar connections
  • modulate immune responses

Can induce enterotoxins
- function for food poising and act to stimulate vagus nerve receptors which induces vomiting

29
Q

Hemolysis B (sphingomyelinase C)

A

Staphylococcus aureus toxin that affects human keratinocytes, polymorphonuclear leukocytes monocytes and T-lymphocytes

Poke holes in all of these cells

30
Q

Leukotoxins

A

Group of Staph aureus toxins that focus on lysing WBCs

Includes but not limited to:

  • PVL
  • gamma-hemolysin
  • Leukotoxin ED
  • Leukotoxin AB/GH
31
Q

Exfoliative toxins

A

Staph aureus toxins that focus on degrading skin cells by braking adhesions

Includes but not limited to the following:

  • epidermolytic toxins
  • specific serine proteases
  • hydrolyses cadherins
  • cleavage of keratinocyte junctions
  • induces skin peeling and blister formation
32
Q

Toxic shock syndrome toxin (TSST-1)

A

Toxin of select staphylococcus aureus species

Elicits superantigens which bind to MHC class 2 and dont let go.
- releases cytokine storms of IL-2, IN-y and TNFs
33
Q

Pyrogenic exotoxins A and C

A

Toxins from Group A B-hemolytic streptococci

Act as superantigens toxins that are very similar to TSST-1

SSA and SmeZ act in similar fashions

34
Q

Streptolysin S and O

A

GAS pore-forming toxins

S targets RBCs, Leukocytes, platelets and subcellular organelles

O targets macrophages, neutrophils, epithelial/endothelial cells
- impaired phagocytic clearance and is cholesterol- dependent

35
Q

Streptococcal pyrogenic exotoxins B (SpeB)

A

GAS toxin

Cysteine/serine protease that cleaves IgG into Fc and Fab fragments (destroyed antibodies other than IgG and compliment)

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