Unit 1: Chapter 18 Microbial Pathogenesis

Question 1

Steps of Pathogenesis

Answer 1

1. Entry
2. Tissue Attachment and Colonization
3. Immune Avoidance
4. Host Damage
5. Pathogen Exit

Question 2

Pathogens are characterized by the presence of __________

Answer 2

virulence factors

Question 3

Virulence Factors

Answer 3

Factors that may help pathogens cause disease in host

The more factors, the more dangerous the pathogen

Question 4

Adhesion

Answer 4

Any microbial factor that promotes attachment

Question 5

Different types of attachment

Answer 5

• Type I Pili/ Fimbriae
• Type IV Pili
• Cell Surface proteins
• Cell envelope components
  
  • Capsule
  • Teichoic Acid (gram positive)
  • Components of Outer Membrane (o-polysaccaride can help attach)

Question 6

Type I Pili/ Fimbriae

Answer 6

Static hairline appendages used only for attachment

The tip binds to a specific substrate on host tissue

Fimbriae and nonplus attachment proteins often collaborate to secure a pathogen to a host cell

Question 7

Adhesion of type I Pili/Fimbriae

Answer 7

Step 1/ Initial Binding: Type I plus attaches to the host cell

Step 2/ Secondary (tighter) binding: Cell surface proteins and host cell receptors (integral)

Question 8

Type IV Pili

Answer 8

Dynamic, thin, and flexible

Repeatedly extend and retract allowing “twitching” movement

Tight secondary binding is facilitated by other surface adhesions

Question 9

Adhesion of type IV Pili

Answer 9

Step 1/ Initial Binding: Type IV pili attaches to cell surface and pulls it closer

Step 2/ Secondary (tighter) binding: Surface Adhesions

Question 10

Bacteria can attach to surfaces in bulk, forming a _______

Answer 10

Biofilm

Question 11

What is a biofilm?

Answer 11

A community of bacteria protected by an external called EPS that allows them to live in hostile environments. Formed in nutrient rich environments and will be flushed by water.

Can be made of anything (sugars, proteins, etc)

Question 12

How is biofilm secreted?

Answer 12

By the bacteria

Question 13

T or F: Biofilms are just single species

Answer 13

False

Biofilms can contain both single species or multispecies of bacteria

Question 14

How do biofilms play an important role in chronic infections?

Answer 14

It helps enables persistent adherence and resistance to bacterial host defenses and antimicrobial agents

EPS protects the cell compared to the cells that may be outside the biofilm

Question 15

T or F: Cell cannot dissolve the EPS and spread

Answer 15

False

They can dissolve the EPS and spread

Question 16

Features of Exotoxins

Answer 16

1. Gram negative and gram positive cells produce exotoxins
2. Enzymes (proteins)
3. Sensitive to heat
4. Secreted by live bacteria
5. Specific to their target cells (ex. neurotoxin)

Question 17

Features of Endotoxins

Answer 17

1. Only gram negative cells produce endotoxins
2. Lipid A
3. Heat- Resistant
4. Released when bacteria dies
5. Non- specific

Question 18

___________ are part of the outer portion of the cell wall of gram negative bacteria

Answer 18

Endotoxins

Question 19

Endotoxins are engulfed by macrophages which secrete ______

Answer 19

Cytokines

Question 20

Endotoxins can cause

Answer 20

Very high fever, vasodilation, activate clotting factors, shock, and death if possible

Question 21

What are the targets are bacterial exotoxins?

Answer 21

• Plasma membrane disruption
• Cytoskeleton alterations
• Protein synthesis disruption
• Cell cycle disruption
• Signal transduction disruption
• Cell-Cell adhesion disruption
• Vesicular trafficking
• Exocytosis

Question 22

What can Staphylococcus alpha toxin cause?

Answer 22

Can cause lysis (bursting) of the host cell by disrupting the plasma membrane

Question 23

How does Staphylococcus alpha toxin disrupt the plasma membrane?

Answer 23

By forming pores or breaking down membrane lipids

Question 24

What are A-B Exotoxin’s

Answer 24

Intracellular Toxins
They bind to a receptor and enter a cell

Question 25

Parts of A-B Exotoxin

Answer 25

B (Binding) region A (Active) portion exerts effects inside

Question 26

A-B Toxin Steps

Answer 26

1. Bacterium produces and releases exotoxin 2. B (binding) component of exotoxin attaches to host cell receptor 3. A-B exotoxin enters host cell by **receptor- mediated** endocytosis 4. A-B exotoxin enclosed in pinched-off portion of plasma membrane during pinocytosis 5. A-B components of exotoxin separate. 6. The A component alters cell function by inhibiting protein synthesis. 7. The b- component is released from the hostel

Question 27

What are two types of A-B Exotoxins?

Answer 27

1. Diphtheria Toxin 2. Cholera Toxin

Question 28

What does diptheria toxin do?

Answer 28

It blocks ribosome function; cell dies It creates toxin when there is decreasing amount of iron

Question 29

What does cholera toxin affect?

Answer 29

It affects cell signaling inside the cell

Question 30

How does cholera toxin affect cell signaling?

Answer 30

Luman has a channel called CTFA that opens when needed to let things in and closes when it doesn't. Cl⁺ and Na⁺ is pumped when channel is open which makes the environment hypertonic and causes H₂O to leave. ATP is used to make cAMP and adenylate cyclase helps make it but is not always active. Adenylate cyclase helps make it but is not always active and AC is made by a G-portion which is also not always active. This causes the channel to open. Basically the G protein is in always on mode, so adenylate cyclase is being produced too much so Na, Cl, and water is being pushed out which leads to diarrhea

Question 31

Is it more difficult to move toxins out a gram negative or gram positive cell?

Answer 31

A gram negative cell because toxins have to move out of 2 membranes (the outermembrane and the inner membrane)

Question 32

Type II Secretion System

Answer 32

System that uses a pilus like structure as a piston to ram proteins through the outer membrane pore structure Pushes protein out in piston manner from inner membrane to periplasm to outer membrane

Question 33

What type of energy does type II secretion use?

Answer 33

ATP

Question 34

Type III Secretion

Answer 34

Some microbes use tiny molecular syringes embedded in their membranes to inject proteins directly into the host cytoplasm Basically sticks the protein directly into the host cell and goes into the cytoplasm of the host directly; no receptors are required so it makes it easy to infect

Question 35

Type IV pili helps aid in \_\_\_\_\_\_\_

Answer 35

Pathogenesis

Question 36

What type of bacteria is is there a wide range of type IV pili?

Answer 36

Gram Negative

Question 37

Can biofilms live in in any surface, living or non living?

Answer 37

Yes they can live on both living and non living surfaces and the biofilm allows for them to live in hostile environments

Question 38

What tissues do biofilms cause the most chronic infections?

Answer 38

Oral, lung, and urogenital

Question 39

Type I Pili/Fimbriae *E.coli* Binding

Answer 39

Step 1/ Initial Binding: Attach to the host Step 2/ Secondary Binding: Via cell surface proteins AND it injects the receptor into the cell Tir proteins Intimin proteins then attach