mechanisms of bacterial virulence

Question 1

what is a pathogen

Answer 1

an organism that causes disease

Question 2

what is pathogenicity

Answer 2

capacity to initiate disease

Question 3

what is virulence

Answer 3

capacity to cause disease and severity of the disease

Question 4

what is transmissibility

Answer 4

ability to transmit from human-to-human to reservoir-to-human

Question 5

what is survival infectivity

Answer 5

ability to breach host defences

Question 6

what are Koch’s postulates

Answer 6

1. Microorganism must be found in diseased but not healthy individuals
2. Microorganism must be cultured from the disease individual
3. Inoculation of a healthy individual with cultured microorganism must cause the same disease
4. Microorganism must be re-isolated from the inoculated, disease individual and matched to original microorganism.

Question 7

what are the steps to infection

Answer 7

transmission 
adherence 
invasion 
survival in host 
tissue damage

Question 8

what secretory systems have the capacity to transfer proteins directly from the cytoplasm

Answer 8

T1SS, T3SS, T6SS and T7SS

Question 9

what secretory systems can only secrete proteins from the periplasm to the outside environment

Answer 9

T2SS, T5SS T8SS T9SS

Question 10

what are the routes of entry for pathogens

Answer 10

respiratory, gastrointestinal, urinary tract, mucus membranes and skin

Question 11

what is adhesion

Answer 11

process by which organisms attach themselves to our cells

Question 12

how is initial attachment of bacteria to cells mediated?

Answer 12

fibrae/pilli and flagella

Question 13

what are EPS?

Answer 13

expolysacchardies they can further mediate attachment of pathogen to cells.

they are hydrophobic structures that displace water promoting closer contact between cells

Question 14

what is invasion

Answer 14

crossing host barriers, extra-cellular environments are harsh environments.

Question 15

what are the two things bacteria produce to induce entry into target cells

Answer 15

zipper and trigger

Question 16

what is zipper

Answer 16

expression of adhesion proteins that bind with high affinity to host receptors.

binding tricks the cell that another one is close by inducing membrane arrangements

bacteria is engulfed

Question 17

what is trigger

Answer 17

bacterial effector proteins are injected directly into the cytoplasm using T3SS.

activates signalling pathways = cytoskeleton rearrangements

Question 18

example of zipper

Answer 18

listeria

Question 19

example of trigger

Answer 19

salmonella and Shiga

Question 20

how do bacteria survive in the host?

Answer 20

1. some escape into the cell cytoplasm rapidly multiplying and escaping to adjacent cells & repeating
2. cytosol is a neutral pH, must have specific adaptations to import metabolic by-products from the cytoplasm
3. bacteria need to hide from host immune responses such as autophagy.
4. avoid lysosomal killing y interfering with endoscope maturation pathway

Question 21

what is the obligate survival?

Answer 21

pathogens require a host to fulfil their life cycle

Question 22

what is facultative survival?

Answer 22

pathogen can live in multiple different conditions

Question 23

what is extracellular survival

Answer 23

pathogens that thrive independent of a host cell

Question 24

example of what pathogens thrive independent of a host cell

Answer 24

E.Coli

Question 25

what are the two types of toxins

Answer 25

exotoxins and endotoxins

Question 26

what are exotoxins

Answer 26

toxins released into the environment can be gram negative and gram positive

Question 27

what are endotoxins

Answer 27

comprised of lipid A or LPS, only gram-negative.

Question 28

how do exotoxins stop self-attacking

Answer 28

they have A/b type subunits

o A+B synthesized and secreted separately
o A-B synthesized separately but associated during secretion
o A/B synthesized together but inactive until cleaved

Question 29

what is LPS and what does it degrade into

Answer 29

lipopolysaccharide is an endotoxin, degrades into non-immunogenic O-antigen and core part and lipid A.

Question 30

what is lipid A

Answer 30

Lipid A is highly pro-inflammatory binds to macrophages and monocytes that initiates a inflammatory response

Question 31

what is the function of endotoxins

Answer 31

responsible for stability and organisation of the cell wall