Microbio Chapter 15- Mechanisms of Pathogenicity Flashcards by claire b🩻

What are portals of entry?

Places where microbes can enter a host

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What are types of portals of entry?

Mucous membrane
Skin
Parenteral route

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Examples of mucous membrane portals of entry?

Repiratory tract e.g Pneumonia
GI tract e.g, E. coli
Genitourinary (GU) tract e.g, HIV
Conjunctiva e.g Pink eye

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Example of bacteria that invades through the skin?

Staphylococcus aureus

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How does bacteria enter a host through parenteral routes?

(Punctured skin)
Insect bite, wound, broken tissue

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What is adherence?

How bacteria attaches to establish a colony and invade a host

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How does a pathogen and host bond?

The host has receptors which the pathogen’s adhesions/ligand’s bind to

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What are host receptors made from?

Complex sugars
-Mannose, fucose

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What are pathogen’s ligands made from?

Glycoproteins or lipoproteins

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What structures (5) on a pathogens help to attach?

Capsule
Fimbrae
M-protein
Mycolic acid
Opa protein

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Example of a bacteria with a capsule?

Streptococcus mutans (teeth decay)

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How does Streptococcus mutans invade?

Enzyme called glucosyltransferase

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S. mutans breaks down what kind of sugar present on teeth?

Sucrose
-from dietary sugar

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What is sucrose broken down into?

Glucose and fructose

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What does glucosyltransferase break down?

Glucose and fructose

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What does glucosyltransferase turn Glucose into?

Glucan

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What does glucosyltransferase turn Fructose into?

Acid

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What does Glucan cause on the surface of teeth?

Plaque (leads to tooth decay)

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What does the broken down fructose acid do to teeth?

degeneration on teeth and loosing of teeth

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Example of bacteria with M-protein?

Streptococcus pyogenes

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What is the purpose of M-protein?

Heat and acid resistance
Attachment
Evade phagocytosis

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What species of bacteria has Mycolic acid?

Mycobacterium sp.

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What is an exoenzyme?

enzyme that is secreted by a bacterial cell and functions outside that cell

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Examples of exoenzymes?

Coagulase
Kinase
Hyaluronidase
Collagenase

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What does Coagulase do?

Coagulate blood (form a clot) Converts fibrinogen to fibrin threads

Example of a bacteria with Coagulase?

Staphylococcus aureus

What does kinase do?

Digest fibrin clots

Example of a bacteria with Kinase?

Streptococcus pyogenes

What does hyaluronidase do?

Hydrolyses hyaluronic acid

Examples of bacteria with hyalyronidase?

1. Clostridium perfringens (gangrene: blackening of the skin) 2. Streptococcus pyogenes

What does Collagenase do?

Hydrolyses (breaks down) collagen

Example of bacteria with Collagenase?

Clostridium perfringens

What is a toxoid?

Inactivated toxin used in a vaccine

What is toxemia?

Presence of toxin used in a vaccine

What is an antitoxin?

Antibody against a specific toxin

What is an Exotoxin?

Proteins produced inside pathogenic bacteria

What kind of bacteria produce exotoxins?

Gram positive and a few gram negative

How are exotoxins produced?

As a part of metabolism (not on the cell wall) -They circulate

What do exotoxins produce?

Specific signs and symptoms | ***Don't cause fever

How are exotoxins neutralised?

The body produces antitoxins called Ig molecules

What are exotoxins chemically change into to use in vaccines?

Toxoids e.g; DTAP vaccine

What are the 3 classes of exotoxins?

1. Classic A-B 2. Membrane disrupting 3. Superantigens

What are classic A-B exotoxins?

-Have two polypeptide chains Chain #1- A Chain #2- B

What is the A polypeptide's function?

the Active part -Causes cell damage -Creates signs and symptoms

What is the B polypeptide's function?

the Binding part (binds to host cell) -Used for entry -Brings A into the cell so it can cause damage

examples of bacteria classic A-B exotoxins?

A. C. diphtheriae (Diphtheriotoxin) B. Botulinum toxin C. Tetanospasmin D. Vibriotoxin

What does A and B do in Diphtheriotoxin?

B- binds to host cell A- Inactivates protein synthesis

How does Diphtheriotoxin damage a cell?

After protein synthesis is deactivated, cell death occurs, a pseudomembrane forms ---> leads to suffocation/ blocks resp. tract

What does A and B do in Botulinum toxin?

B- binds to host cell A- becomes a neurotoxin.

What does A in Botulinum toxin inhibit?

Acetylcholine in neuromuscular junction -No action potential/nerve movement -muscles freeze

What does botulinum toxin cause?

Flaccid paralysis

What does A and B do in Tetanospasmin?

B- Binds to host cell A- becomes a neurotoxin

What does A in Tetanospasmin inhibit?

GABA (neurotransmitter that allows muscles to relax)

what does Tetanospasmin cause?

Severe spasms Stages 1- Lock jaw 2- Opisthosomas (spinal fracture; end stage tetanus) 3- CV and respiratory affected

What does A and B do in Vibriotoxin?

B- binds to host INTESTINAL cells A- Converts cells into little pumps (secondary cyclic AMP system) and pumps out water

What does Vibriotoxin cause?

Rice water stools

What are membrane-disrupting toxins?

Disrupt plasma membrane by forming holes in it (cell content leave) -2 ways

What are 2 ways a membrane-disrupting toxin can form a hole in the plasma membrane?

1. Disrupting the phosphilipid bilayer 2. Creating protein channels

Example of membrane-disrupting toxins?

Hemolysins leukocidin Erythrogenic toxin

What does hemolysis disrupt?

Red blood cells e.g blood agar ---> clear zone

What does Leukocidin disrupt?

Leucocytes (white blood cells)

What does erythrogenic disrupt?

Membrane of skin and blood vessels

What does erythrogenic toxin cause?

Scarlet fever -Red skin rash

What bacteria has hemolysis, leucocidin and erythrogenic?

Streptococcus pyogenes

What are superantigens?

provoke an intense immune response

How do superantigens function?

trigger T-cells to activate and over release cytokines (Interleukins) which circulate in the blood to vital organs (especially GI tract)

What symptoms do superantigens cause?

Nausea, vomitting, diarrhoea and shock

Example of bacteria with a superantigen?

Staphylococcus aureus

What does staphylococcus aureus cause?

1. TSS 2. Food poisoning

What is an endotoxin?

Lipid portion of LPS is released when cell dies and cell wall lyses

What is the name of the lipid that is an endotoxin?

Lipid A

What kind of bacteria can have an endotoxin?

only Gram- negative

What symptoms does endotoxins cause?

Fever GI tract (nausea, vomiting, diarrhoea and dysentry) Shock

Do endotoxins promote the formation of antitoxins (Immunoglobulins Ig)

No they don't -Antibodies can be produced but won't counter the effect of the toxin

What triggers a fever?

When Gram negative bacteria is digested by a macrophage

What do lysosomes do to trigger a fever?

Lysosomes degrade (w/ enzymes) the bacteria cause the LPS (lipid A) to be released

When LPS is released what does it trigger in a fever?

Triggers the release of interleukin-1(a cytokine) -IL-1 is over released therefore is toxic

Where does IL-1 in the blood travel to during a fever?

The brain and specifically the Hypothalamus

What does the hypothalamus secrete during a fever?

Prostaglandins -Which tell the body to reset its temperature to a high temperature Causing a fever

What are the two stages of fevers?

1. Chills stage 2. Crisis stage (stages work in a cycle)

What is the Chills stage?

Lots of IL-1 in blood Leads to shivering

What is the Crisis stage?

IL-1 decreases in the blood -Sweating

How is septic shock triggered?

Gram-negative bacteria is digested by a macrophage causing LPS to be released

What does the release of LPS trigger in shock?

TNF (tumor necrosis factor) or Cachetin

What does TNF/Cachetin do?

Travels to vital organs via blood and changes the permeability of their blood vessels (BP drops drastically)