Microbial Pathogenicity- Chapter 15

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The Mechanisms of Pathogenicity
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1

To cause disease, a pathogen must do these three things?

Enter host

Attach to host cells

Damage host cells

All while escaping destruction by the immune system

2

What are virulence factors?

Characteristics of a microbe that allow it to cause disease. May assist in entry, attachment, damage, or evading the immune system.

3

What is the parenteral route of infection?

Microbes deposited directly underneath the skin or mucous membrane by needles, surgical or other wounds, etc.

4

What is meant by preferred portal of entry?

A bacteria introduced to one part of the body may grow and cause disease but when that same bacteria is introduced to a different part it may not.

5

What does ID50 mean?

The number of microbes that will cause disease in 50% of the population, if they were to be exposed to it.

6

Bacterial capsules what are they and what do they do?

Thick layer of slimy material that covers the outside of the bacterium and makes it difficult to phagocytize.

7

What cell components can help bacteria evade destruction?

M proteins, make the bacteria resistant to heat and acid

Waxy lipids- make bacteria resistant to digestion inside phagocytes

8

What extracellular enzymes can combat the immune defenses?

Coagulase- help form blood clots that bacteria can hide inside

Kinases- break down blood clots that the host has formed to prevent pathogen spread

9

What extracellular enzymes can combat the immune defenses?

IgA proteases- breaks down antibodies

10

What is antigenic variation?

By constantly changing its antigens, a pathogen can evade the adaptive immune defenses.

11

How is antigenic variation done?

By activating the expression of alternate genes

By exchanging DNA with other variants of the same species

12

What is the name of the surface protein that when triggered causes non-phagocytic host cells to engulf a phathogen?

Invasins

13

Why are invasins good for some pathogens?

Help them hide inside of a cell

14

Surface molecules on pathogens called ______ or ________, bind specifically to complementary surface receptors on cell certain host tissues.

Adhesins Or ligands

15

What are biofilms?

hint not 90's films staring Polly Shore

A group of microbes plus their sticky extracellular products, that can adhere to host cells

16

This protein secreted by pathogens tightly binds to iron in host hemoglobin robbing it of nutrients that the host needs.

Siderophores

17

What does LD50 mean?

A dose that would be lethal for 50% of people.

18

To types of toxins?

Exotoxins

Endotoxins

19

Exotoxins Vs Endotoxins

Produced inside pathogen and released

Part of the bacterial cell wall released when the bacteria is broken down

20

How do A-B toxins work?

Made up of two proteins these toxins attach to the cell with one subunit (B) to gain entry to the cell. Once inside of the cell the first subunit (A) is released into the cytoplasm and the other is returned to the extracellular matrix.

21

A toxin that causes the lysis of host cells by disrupting their cell membranes

Membrane-disrupting toxins

22

What are Superantigens?

•cause an intense immune response that can lead to severe inflammation, fever, vomiting, diarrhea, and sometimes shock and death

23

Cytopathic Effects

...

24

syncytia

...

25

•Viruses have a variety of cell-damaging strategies:

Cytopathic Effects

–Stopping synthesis of important macromolecules–Causing digestive enzymes to be released from the lysosome–Fusing of infected cells to form syncytia–Inducing changes in the host cell DNA