Bacterial infection 2

Question 1

Invasion

Answer 1

Pathogen moving into or through mucosal epithelium

to reach site of infection

Question 2

Biofilm

- define

Answer 2

= surface-associated multicellular communities

in host tissues or medical devices

Cells embedded in exopolymeric matrix

Question 3

Biofilm formation

- role

Answer 3

Protection from enviro stress

e.g IS or ABs

Question 4

EPEC main site of infection

Answer 4

Mucosal membrane

Question 5

Invasion

- 3 options for a bacterial cell that’s attached themselves to an epithelial cell

Answer 5

>Enter host cells + pass through 
>Move between host cells
- disrupt tight junctions 
= more permeable 
>Intracellular = remain within cells

Question 6

Intracellular invasion

Answer 6

Enter host cells

Survive within host cells

Move through host cells

• > exit cells
• > spread to other cells

(Need to be able to overcome our systems to exclude them)

Question 7

Mechanisms for entry into host cells

Answer 7

Active mechanisms
= zipper + trigger

Induce uptake by host

Question 8

Zipper + trigger cause

Answer 8

Cytoskeleton reorganisation (actin)
-> changes cell shape

Question 9

Zipper

Answer 9

Exploits host cell receptors used for normal functions
- e.g. E-cadherin important in forming junctions between cells

Signals to host cell proteins

• > induces polymerisation of actin
• > forms endosome
• > engulfs bacteria

Question 10

Trigger

Answer 10

T3SS- dependent

Inject efforts into host cells

• > trigger host cytoskeleton reorganisation
• > forms phagocytic cup
• > internalises bacteria

Question 11

Trigger

e.g. Salmonella

Answer 11

Encoded on PAI 1 (=SPI-1)

Encodes 13 effectors

Question 12

Phagocytosis

Answer 12

Inhibit bacteria growth:
- nutrient limited + acidic

Fuse w/ lysosomes
-> releases lysozyme, proteases + defensives into phagosome

= destruction

Question 13

3 strategies to surviving inside host cell

Answer 13

1. Adapted to survive phagosome-lysosome fusion
2. Break out of phagosome before lysosome fusion
3. Prevent lysosome fusion

Question 14

Salmonella intracellular survival by…

Answer 14

Blocks maturation of phagosome
+ fusion w/ lysosome

Forms a SCV
= Salmonella Containing Vacuole

Question 15

SPI 2 encodes…

= Salmonella PAI 2

Answer 15

Encodes functions that allow pathogen to alter phagosome properties

A T3SS + effectors infected into cell
- can prevent lysosome fusion

Question 16

SPI-2 effectors

- when injected into host cytoplasm…

Answer 16

1. Can initiate apoptosis
2. Can down regulate inflammation
3. Can modify surface of SCV
   -> lysosome fusion blocked
   (+ bacteria can exit cell when vesicle fuses w/ cell periphery)

Question 17

SPI 1 + 2

Answer 17

Have to be coordinated to the different stages of infection

-> so use the right virulence factors at the right time

Question 18

Escape from phagosome into cytoplasm

- L. monocytogenes

Answer 18

Encodes Listeriolysin O (LLO)

At pH 5.5. in phagosome
–> LLO forms pore in phagosome membrane

Works with phospholipase enzymes to break open phagosome

Question 19

How Listeria spread to adjacent cells

Answer 19

Listeria then polymerise host cel actin

-> propel through cytoplasm

Question 20

Q fever

• caused by
• transmission

Answer 20

Coxiella burnetii

Transmitted by deer ticks, illation, ingestion, wound contamination

Question 21

Coxiella burnetii

- features

Answer 21

Obligate intracellular pathogen

Allows lysosome fusion
-> adapted to grow in acidic + nutrient-limited conditions

Modifies phagosome
= Coxiella Containing Vacuole
(CCV)

Question 22

Coxiella burnetii

- effects on CCV

Answer 22

Expands CCV by fusion w/ other CCVs + endoscope
= Large Cell Variant (LCV)

Can be dramatic + take up lots of cell volume

Question 23

Coxiella burnetii

- promotes cell survival

Answer 23

Suppresses apoptosis

Question 24

Life cycle of Chlamydiae

Answer 24

Elementary body
= infectious form
- metabolically inactive

Reticulate body
= replicative form
- metabolically active