M2 Basis of Infectious Disease

Question 1

Define the term Gram-negative bacteria

Answer 1

bacteria which has only 1-3 layers of peptidoglycan but has a lipopolysaccharide outer layer

Question 2

Define the term Gram-positive bacteria

Answer 2

bacteria which has many multiple layers of peptidoglycan

Question 3

Role of outer membrane of gram negative bacteria in sepsis

Answer 3

lipopolysaccharides, aka bacterial endotoxin

Question 4

Explain the term pathogenesis

Answer 4

the ability of endogenous bacteria to shift to a parasitic lifecycle through adaptation

Question 5

What is bacterial adhesion?

Answer 5

The adhesion of bacterial ligands to adhere to receptors on the host’s cells

Question 6

What are the 5 things that bacteria must do to evade host defences?

Answer 6

• Immunity at mucosal surfaces
• Destroy immune cells
• Interfere with inflammatory response
• Evade innate immunity
• overome acquired immunity

Question 7

Give the main features of a bacterial capsule

Answer 7

• secreted layer external to outer membrane and cell wall
• is a polysaccharide layer
• immunogenic

Question 8

Give 3 abilities that bacterial capsules have to fight immune response

Answer 8

• interfere with deposition of complement
• can mask antibodies
• composition can mimic host

Question 9

Explain the term acquired immunity

Answer 9

immunity through memory pretty much

Question 10

Give the 2 ways that bacteria can overcome acquired immunity

Answer 10

Phase variation

Antigenic variation

Question 11

Explain Phase variation

Answer 11

switching between on and off to control a gene

Question 12

Explain Antigenic variation

Answer 12

allows the bacterium to change the sequence of a gene

Question 13

Give an example of a bacteria that uses Phase variation

Answer 13

Salmonella

Question 14

Give an example of a bacteria that uses Antigenic variation

Answer 14

Neisseria gonorrhoeae Pili

Question 15

Give the 6 ways in which infection can spread

Answer 15

superficial
systemic
extracellular
intracellular
general contact
injection

Question 16

Give the 2 methods of bacterial intracellular invasion

Answer 16

Zipper mechanism

Trigger mechanism

Question 17

how does the zipper mechanism of bacterial intracellular invasion work?

Answer 17

through ligand binding and membrane engulfment

Question 18

how does the trigger mechanism of bacterial intracellular invasion work?

Answer 18

through T3SS needles on the bacteria injecting into the cell membrane

Question 19

If the bacteria penetrates blood vessel endothelium, what is the result?

Answer 19

bacteria circulate in blood

Question 20

If the bacteria penetrates phagocytic cells, what is the result?

Answer 20

bacteria establish new sites of infection

Question 21

If the bacteria penetrates lymphatic tissue endothelium, what is the result?

Answer 21

bacteria accumulate in lymph nodes

Question 22

what are the basic building blocks of a lipopolysaccharide?

Answer 22

Lipid A
Core polysaccharide
O-antigen

Question 23

what is the main role of lipopolysaccharides on the outer membrane of gram-negative bacteria?

Answer 23

to bind to receptors on macrophages, B cells and other cells that stimulates release of acute phase inflammatory cytokines

Question 24

what is 1 main symptom of sepsis?

Answer 24

fever

Question 25

Explain the term spore and give an example

Answer 25

inert structures, resistant to physical and chemical challenge, e.g. C difficile

Question 26

What type of bacteria is Clostridium spp.?

Answer 26

Gram positive, anaerobic

Question 27

Where is Clostridium spp. found?

Answer 27

found in faeces and soil

Question 28

What does Clostridium spp. produce?

Answer 28

Spores that can survive outside the body for many months and can cause severe tissue damage

Question 29

Give 3 infections that are caused by Clostridium spp.

Answer 29

Diarrhoea - antibiotic associated Gangerene Tetanus

Question 30

Explain the term biofilm

Answer 30

a complex community of bacteria found on surfaces e.g. hard surfaces of the mouth