Bacteria pathogenesis

Question 1

Pathogen

Answer 1

organisms capable of causing disease

Question 2

Disease

Answer 2

clinical signs and symptoms of damage that occur in a host as a result of its interaction with an infectious agent

Question 3

Overt/strict pathogens

Answer 3

only associated with human disease, not found as members of normal microbial flora.

Question 4

Opportunistic pathogens

Answer 4

members of normal flora that only cause disease when in the right conditions/introduced into unprotected sites.

Question 5

Facultative pathogens

Answer 5

can grow and survive in the environment as well as in the host. doesn’t have to cause disease to survive in environment (the ‘accidental host’)

Question 6

what do virulence factors do?

Answer 6

facilitate the colonisation, growth and spread of bacteria in host

Question 7

Areas of the body that should be microbe free

Answer 7

fluids: blood, CSF, urine

Tissues/organs: muscles, glands, brain etc

Question 8

LD50

Answer 8

lethal dose 50: dose that gives 50% mortality in animal model

Question 9

infective dose vs lethal dose

Answer 9

ID = dose at which you get infection
LD = dose at which you die

Question 10

Sub-clinical infection

Answer 10

Bacteria are present but no pathology

Question 11

Name 6 examples of virulence factors in bacteria

Answer 11

1. Adhesins: fimbriae, pili, outer membrane proteins
2. Flagella for motility
3. Help to obtain essential nuritents (e.g. siderophores)
4. Toxins
5. Capsule
6. Type III secretory molecules

Question 12

Give an ex of a bacteria which is an extracellular pathogen

Answer 12

Streptococcus pneumoniae

Question 13

Ex of toxin producing bacterium

Answer 13

Clostridium botulinum
Clostridium tetani
Vibrio cholera
E.coli

Question 14

Ex of an intracellular bacterium

Answer 14

Salmonella enterica serovar Typhimurium

Listeria monocytogenes

Question 15

Virulence factors of S.pneumoniae

Answer 15

Capsule
Surface adhesions
Secretory IgA protease
Neuroaminidase
Pneumolysins (pore forming)

Question 16

Endotoxin

Answer 16

On bacteria surface

Question 17

Ex of endotoxin

Answer 17

LPS on Gr- bacteria

Question 18

What receptor can detect LPS?

Answer 18

TLR4 (toll-like receptor 4)

Question 19

What is LPS an example of?

Answer 19

PAMP

Question 20

General symptoms of LPS

Answer 20

fever, diarrhoea, vomiting

Question 21

Ex of bacteria that has LPS endotoxin

Answer 21

Salmonella

Question 22

Exotoxin

Answer 22

Toxin released extracellular

Question 23

Which is generally more toxin, endo or exo toxin?

Answer 23

Exotoxin

Question 24

Which is generally more heat stable, endo or exo toxin?

Answer 24

Endotoxin

Question 25

Enterotoxin

Answer 25

group of exotoxins that act on the small intestine

Question 26

Ex of bacterium that release enterotoxins

Answer 26

C.dif Cholera toxin E.coli

Question 27

Toxoid

Answer 27

inactivated toxin useful as a vaccine

Question 28

Which bacteria has beta-haemolysin?

Answer 28

Streptococcus pyogenes

Question 29

Botulinum toxin is an example of a...

Answer 29

Neurotoxin

Question 30

Clostridium botulinum is a...

Answer 30

G+, spore forming anaerobe

Question 31

Symptoms of botulinum toxin

Answer 31

``` flaccid paralysis (floppy baby) Respiratory arrest ```

Question 32

What does botulinum toxin do?

Answer 32

Blocks release of Ach

Question 33

Clinical use of botulinum toxin

Answer 33

``` Relief of spasticity Chronic migraine Excessive sweating Overactive bladder Botox ```

Question 34

Is vibrio choleae Gr- or Gr+?

Answer 34

Gr-

Question 35

What does cholera toxin do?

Answer 35

- conformational change of G protein - adenyl cyclase constantly activated - increase cAMP - Cl- and Na+ into lumen, water follows

Question 36

Cholera toxin results in

Answer 36

massive loss of fluid and electrolytes

Question 37

4 strategies used by bacteria to evade immune system

Answer 37

- Hide: intracellular - Antigenic variation and phase variation: change immunogeneicty to avoid established immune response - Molecular mimicry - Modify or block host response

Question 38

3 ex of bacteria modifying/blocking host immune response

Answer 38

1. capsule - phagocytosis 2. IgA protease - antibody 3. Type III secreted effectors - cell signally

Question 39

Ex of pathogen which undergoes molecular mimicry

Answer 39

Haemophilus influenzae

Question 40

Molecular mimicry may trigger...

Answer 40

Autoimmunity

Question 41

Extra genome sequence, regions of DNA unique to a set or related pathogens usually transferred via horizontal gene transfer =

Answer 41

Pathogenicity islands