Microbio Chapter 15- Mechanisms of Pathogenicity Flashcards
What are portals of entry?
Places where microbes can enter a host
What are types of portals of entry?
- Mucous membrane
- Skin
- Parenteral route
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
Example of bacteria that invades through the skin?
Staphylococcus aureus
How does bacteria enter a host through parenteral routes?
(Punctured skin)
Insect bite, wound, broken tissue
What is adherence?
How bacteria attaches to establish a colony and invade a host
How does a pathogen and host bond?
The host has receptors which the pathogen’s adhesions/ligand’s bind to
What are host receptors made from?
Complex sugars
-Mannose, fucose
What are pathogen’s ligands made from?
Glycoproteins or lipoproteins
What structures (5) on a pathogens help to attach?
- Capsule
- Fimbrae
- M-protein
- Mycolic acid
- Opa protein
Example of a bacteria with a capsule?
Streptococcus mutans (teeth decay)
How does Streptococcus mutans invade?
Enzyme called glucosyltransferase
S. mutans breaks down what kind of sugar present on teeth?
Sucrose
-from dietary sugar
What is sucrose broken down into?
Glucose and fructose
What does glucosyltransferase break down?
Glucose and fructose
What does glucosyltransferase turn Glucose into?
Glucan
What does glucosyltransferase turn Fructose into?
Acid
What does Glucan cause on the surface of teeth?
Plaque (leads to tooth decay)
What does the broken down fructose acid do to teeth?
degeneration on teeth and loosing of teeth
Example of bacteria with M-protein?
Streptococcus pyogenes
What is the purpose of M-protein?
Heat and acid resistance
Attachment
Evade phagocytosis
What species of bacteria has Mycolic acid?
Mycobacterium sp.
What is an exoenzyme?
enzyme that is secreted by a bacterial cell and functions outside that cell
Examples of exoenzymes?
- Coagulase
- Kinase
- Hyaluronidase
- Collagenase
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?
- Clostridium perfringens (gangrene: blackening of the skin)
- 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?
- Classic A-B
- Membrane disrupting
- 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?
- Disrupting the phosphilipid bilayer
- 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?
- TSS
- 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?
- Chills stage
- 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)
