Pathogens Host Defenses Flashcards Preview

Microbiology Final > Pathogens Host Defenses > Flashcards

Flashcards in Pathogens Host Defenses Deck (103)
Loading flashcards...
1

What are pathogens?

Microorganisms capable of causing disease/damage to the host.

2

Do all strains of one species have the same ability to cause disease?

No

3

What is a pathogen usually identified by?

The set of virulence genes that it carries and expresses

4

What is virulence?

A measure of the ability to cause damage to the host

5

What 2 factors is virulence determined by?

Invasiveness, toxigenicity

6

What is invasiveness?

The ability of microorganisms to become established in the host, or overcome the host defenses and to spread in the tissues

7

What is toxigenicity?

the capacity of the microorganism to produce substances known as toxins that damage specific tissues of the host

8

What happens once a host is exposed to a pathogen? 5 steps

1. Adherence to skin or mucosa
2. Invasion through epithelium
3. Growth and colonization (production of virulence factors)
4. Toxicity or Invasiveness
5. Tissue damage, disease

9

What are the 5 different types of virulence factors that pathogens use to invade host tissues?

1. adhesins
2. capsules
3. enzymes that destroy host tissues
4. Invasins
5. Type 3 Secretion Systems (T3SS) and Type 4 Secretion Systems (T4SS)

10

What do adhesins promote?

Specific attachment to host cell surfaces

11

How many cell types is one adhesin normally able to attach to?

one or many

12

What are Fimbriae/Pili? What do they mediate?

Polymers that mediate loose attachment

13

What are Afimbrial adhesins?

(not filaments) mediate close attachment

14

In what 2 ways do capsules aid pathogens?

1. They prevent them from being destroyed by host immune cells (phagocytes)
2. They help them attach to host cells and to other bacteria

15

What are 2 essential virulence factors for some bacterial pathogens?

Streptococcus pneumonia, Haemophilus influenzae

16

What is epidermis?

The outer layer of skin

17

How do most pathogens infect humans?

They penetrate the epidermis by using breaches in the skin (wounds, surgery, catheter)

18

What happens when pathogens penetrate the mucosa?

They destroy the single-cell layer or invade the cells themselves

19

What is hyaluronidase? Function?

An extracellular enzyme that degrades hyaluronic acid

20

Which pathogens release hyaluronidase?

Staphylococci, streptococci, clostridia

21

What is hyaluronic acid?

A sticky polysaccharide that holds host cells together

22

What is collagen? Function?

An extracellular enzyme that degrades the protein collagen present in connective tissues (muscle, cartilage)

23

What is the function of lecithinase? Causes the lysis of what?

An extracellular enzyme that degrades lecithin (phosphatidylcholine) in cell membranes -- causes the lysis of RBCs and destroys tissue cells

24

What is gas gangrene?

The term used to describe the decay or death of an organ or tissue caused by lack of blood supply in wounds infected by anaerobic bacteria

25

What microorganism are present in gas gangrene? What do they do?

Clostridium perfringens. They break down tissue by gas production.

26

What type of microorganism are Clostridium perfringens?

strict anaerobes

27

What enzyme do Clostridium perfringens use to lyse host cells in gas gangrenes? What enzymes do they use to destroy the extracellular matrix?

Lecithinase

28

What are hemolysins? What are the different types of hemolysins?

A substance in the blood that destroys RBCs and liberates hemoglobin.

Enzymes, cytolysins

29

What are two examples of hemolysin enzymes?

Lecithinase, phospholipase

30

What is a characteristic of hemolysin cytolysins?

Pore-forming