6.2 Bacteria As Pathogens

Question 1

What is a pathogen

Answer 1

A disease chasing microorganism
Can invade and cause harm to host tissues

Question 2

How do pathogens get into the body

Answer 2

Must penetrate host interface with environment (interface is a surface or boundary linking two environments)
e.g. lining of digestive system or gas exchange system

Question 3

How does the body prevent entry of pathogens

Answer 3

Mucus- thick later and is hard to penetrate
Enzyme- break down the pathogen
Stomach acid- kills microorganism

Question 4

How do bacterial pathogens cause disease

Answer 4

1- produce exotoxins
2- produce endotoxin
3- host tissues invasion

Question 5

What is gram staining

Answer 5

A strain which differentiates between two types of bacteria based on cell wall structure

Question 6

Gram + bacteria

Answer 6

Thick layer of peptidoglycan
Just inner membrane (no outer)
Has teichoic acid and a periplasmic space
Does not produce endotoxins

Question 7

Gam - bacteria

Answer 7

Thin layer of peptidoglycan
Outer and inner membrane
More lipopolysaccharide

Question 8

What does gram staining detect

Answer 8

Peptidoglycan barrier

Question 9

What is the advantage of the more complex structure of Gram- cell walls

Answer 9

Extra protection from the action of antibacterial agents e.g. lysozyme and penicillin

Question 10

How does penicillin kill bacteria

Answer 10

Effects formation of cross linkages in cell wall
Wall is weakened so osmotic changes occur
Cell lysis

Question 11

Which bacteria use endotoxin

Answer 11

Gram -

Question 12

Which bacteria use exotoxins

Answer 12

Gram+ and Gram-

Question 13

What is the relationship of endotoxin and bacteria cell

Answer 13

Part of cell surface membrane

Question 14

What is the relationship of exotoxin and bacteria cell

Answer 14

Secreted by cell

Question 15

Chemical nature of endotoxin

Answer 15

Lipopolysaccharide

Question 16

Chemical nature of exotoxin

Answer 16

Polypeptide or protein

Question 17

Which toxin has higher potency

Answer 17

Exotoxin

Question 18

Which toxin can be denatured

Answer 18

Exotoxin

Question 19

Action of endotoxin

Answer 19

Once released, usually from bacterial cell death, causes inflammation and cell death

Question 20

Action of exotoxin

Answer 20

Destroy cell membrane or overstimulate the immune system (cytokine storm)

Question 21

Infections associated with endotoxin

Answer 21

Salmonella

Question 22

Infections associated with exotoxin

Answer 22

Staphylococcus aureus

Question 23

O specific competent of endotoxin

Answer 23

Lives outside cell membrane
Needed to infect and invade host

Question 24

Effects of endotoxin

Answer 24

Effects are around infection site
Symptoms include fever, vomiting and diarrhoea (bc cells don’t absorb water)
Take a few hours for symptoms

Question 25

Use of antibiotics to treat endotoxins

Answer 25

Use bacteriostatic To recent further cell death and release of endotoxin in cell lysis Prevents worsening symptoms

Question 26

Is endotoxin denatured in cooking

Answer 26

Yes Because high heat denatures enzymes and kills bacteria

Question 27

Which gram if bacteria produce staphylococcus

Answer 27

Positive

Question 28

Are exotoxins soluble

Answer 28

Yes so easily transported around the body causing widespread effects

Question 29

How do exotoxins get released and infect

Answer 29

Produced and secreted as part of normal growth and metabolism to colonise host Bind to specific receptors on host cell

Question 30

Antigenic properties of exotoxins

Answer 30

Highly antigenic so stimulation production of antitoxins which inactivate them

Question 31

What is an antitoxin

Answer 31

Bind and neutralise toxin by preventing receptor binding

Question 32

TB full name

Answer 32

Mycobacterium tuberculosis

Question 33

How does mycobacterium tuberculosis cause disease

Answer 33

Host tissue invasion

Question 34

What does mycobacterium tuberculosis infect

Answer 34

Phagocytes in the lung

Question 35

Why is the first invasion normally symptomless

Answer 35

Infected phagocytes are sealed in tubercles as a result of inflammatory response of the lungs

Question 36

What occurs during mycobacterium tuberculosis dormancy period

Answer 36

Bacteria not destroyed by immune system bc of thick waxy coat produced protecting them from macrophage enzymes

Question 37

penicillin

Answer 37

only effects gram + because gram + has a thick cell wall interferes with the formation of cross links during synthesis of cell walls so bacteria is susceptible to osmotic shock