Bacterial Pathogenesis

Question 1

Pathogenicity

Answer 1

ability to cause disease

Question 2

Infection

Answer 2

Host response - inflammation: Pain, Red, Immobility, Swelling, Heat

Question 3

Endogenous infection

Answer 3

infection by member of NF

Question 4

Exogenous infection

Answer 4

Infection not by a member of NF

Question 5

Local infection

Answer 5

infection restricted to an area

Question 6

Focal infection

Answer 6

localised infection but the pathogen releases by-products that can spread to other parts of body e.g. tetanus

Question 7

Systemic infection

Answer 7

Infection spread throughout the body by organism and their by-product

Question 8

Primary infection

Answer 8

initial infection caused by one pathogen

Question 9

Secondary infection

Answer 9

infection that follows primary infection e.g. may contract another infection because immune sys. is weak from 1º infection: cold -> flu

Question 10

Latent infection

Answer 10

Infection that one may have but symptoms arise at a later date

Question 11

Acute infection

Answer 11

rapid @ start & more severe e.g. measles

Question 12

Chronic infection

Answer 12

Slow progressive disease e.g. TB

Question 13

Commensals (refer to microbes)

Answer 13

rarely cause disease

Question 14

Define Pathogen and list 3 types

Answer 14

may cause disease in normal host.

3 O’s: Opportunistic; Obligate; Overt

Question 15

Opportunistic pathogens

Answer 15

a microbe that can become pathogenic under circumstances like if body is immunocompromised (weak immune sys)

Question 16

Obligate pathogen

Answer 16

Always cause disease => transferred from one host to another = survive

Question 17

Overt pathogen

Answer 17

organism that is ALWAYS regarded as pathogenic by clinical labs

Question 18

What is ID50 and what does it measure?

Answer 18

Infectious dose 50: measure # of bacteria to infect 50% of population of animals exposed (NOTE: Lo val. = more virulent)

Question 19

What is LD50 and what does it measure?

Answer 19

Lethal dose 50: measure # of bacteria to kill 50% of population of animals exposed (NOTE: Lo val. = more virulent)

Question 20

Which virulence factors in pathogens aids in attachment to body surfaces?

Answer 20

Glycocalyx (Capsule and slime layer); pili and fimbrae

Question 21

Explain the emergence of Haemophilius influenzae as a secondary pathogen?

Answer 21

H. influnzae becomes a secondary pathogen if the host’s immune defences are weak due to the response to a primary pathogen: cold-> flu

Question 22

What is glycocalyx and how can this contribute to the virulence of a pathogen?

Answer 22

capsule/slime layer made up of glycoproteins and /or polysaccharides.&raquo_space; sticky = adherence= resist cough reflex; resist phagocytosis (too big for macrophages)

Question 23

How may collagenase act as a virulent factor?

Answer 23

Break down collagen in connective tissue = allow pathogen to spread to neighbouring tissues

Question 24

What is the basis of vaccine for tetanus?

Answer 24

Exotoxin from clostridium tetani converted into toxoids for vaccine: heat treated or formalin treated (= to stimulate primary immune resp.)

Question 25

Why does a single molecule of diptheria toxin subunit A lead to death of host cell?

Answer 25

subunit A interferes w/ elongation factor 2 (EF-2) = inhibit protein synthesis= cell can’t make new proteins = repeats process until all ribosome is blocked enzyme not consumed) = cell dies.

Question 26

What gram stain is the Vibrio species and a feature it has?

Answer 26

Gram neg baccilli. Motile- single polar flagella

Question 27

What does ENTEROTOXIN (endotoxin of Vibrio cholera) do to the human body?

Answer 27

1. enterotoxin binds to GM1 (mucosal cells of SI)
2. A1 goes in SI via A2 subunit
3. A1 stimulates intracellular cAMP production
4. = Excrete ions (K+, Cl-,Na+, HCO3-) = water follows ions = large fluid loss

Question 28

What 2 places were majorly affected by cholera?

Answer 28

Yemen & Haiti

Question 29

The serotype of Vibrio cholera

Answer 29

Variable O antigen

Question 30

Cholera toxin component and their roles

Answer 30

5 beta units, one alpha subunit w/ the A2 bridging piece and an active component A1

Question 31

How does fibrinolysin act as a virulence factor?

Answer 31

DIssolves fibrin clot preventing a phagocyte from capturing the pathogen

Question 32

What type of exotoxin binds one portion of the host cell receptor while another portion enters the cell w/ enzyme activity to cause toxicity?

Answer 32

AB toxin

Question 33

Describe how antibody works as normal vs w/ protein A on bact. surface

Answer 33

Normal

1. Fab portion (Antibody) binds to epitope (antigen) which is the
2. antibody presents to phagocyte (Fc portion binds to receptor on macrophage)
3. Bact. engulfed

w/ Protein A

1. Fc portion (bottom of antibody) binds to Protein A (antigen)
2. Fab portion presented to cell but not recognised bc Fc portion can’t bind on receptor
3. Bact. can’t be engulfed

Question 34

Give 3 examples each of indirect contact and fomite transmission

Answer 34

Indirect: food, water, soil

Fomite (inanimate objects): splinters, blankets, clothing, furniture surfaces

Question 35

define immunogenicity

Answer 35

ability for antigen to spark an immune response from host