lecture 33

Question 1

what does pathogenicity mean

Answer 1

the ability for something to cause disease

Question 2

what are the Koch’s postulates

Answer 2

guidelines that are used to demonstrate that a specific pathogen causes specific symptoms of disease

Question 3

what are the exceptions to Kochs postulates

Answer 3

the fact that not all microbes can be cultured and re-inserted into an organism and the fact that pathogenic bacteria can be found in healthy people.

Question 4

what does the finding of pathogenic bacteria in healthy people imply

Answer 4

it implies certain strains of disease causing microbes have specific virulence factors that aren’t present in all bacterial strains

Question 5

what are the key stages of pathogenesis

Answer 5

1: the microbe must adhere to host cells
2: the microbe must invade the host tissue
3: the microbe will then replicate in the tissue and colonise it
4: when the population is large enough, the population is able to cause disease. this can be done by toxins or by direct tissue damage.

Question 6

what virulence factors help with step one of pathogenicity

Answer 6

the many tiny fimbriae on the membrane of the bacteria.

Question 7

what does fimbriae specificity mean

Answer 7

it means that the bacteria will only bind to specific cell tissues.

Question 8

whats an example of bacteria with fimbriae virulence factor

Answer 8

Neisseria gonorrhoeae

Question 9

what virulence factor is associated with stage 2 of pathogenicity

Answer 9

one factor helping this is the flagella. There are also internalin related proteins, these proteins are used to get into the tissue

Question 10

how does flagella aid the host tissue invasion

Answer 10

it helps the bacterias motility through mucus of tissue

Question 11

what virulence factors help step 3

Answer 11

associated virulence factor could be the capsules Another virulence factor that aids this stage are siderophores,

Question 12

how does the capsule virulence factor aid pathogenicity

Answer 12

it prevents the bacteria from being phagocytosed

Question 13

how do the siderophores aid the pathogenicity

Answer 13

one example of siderophores Yersinia bactin solubilises metal bound to host proteins and transports it to the bacteria

Question 14

whats an example of a siderophore

Answer 14

Yersiniabactin

Question 15

what virulence factors help in stage 4

Answer 15

endotoxins and exotoxins

Question 16

what are endotoxins

Answer 16

things like the lipopolysaccharide on the bacteria or proteins from the membrane. components of the gram negative bacteria

Question 17

what bacteria type do endotoxins come from

Answer 17

gram-negative

Question 18

how do endotoxins work

Answer 18

they are apart of the normal bacteria, but when the bacteria dies and degrades these toxins cause a very strong immune response, so they cause innflamation

Question 19

describe exotoxins and their three sub catagories

Answer 19

toxins that are produced within the bacteria then released. can come in the form of cytotoxins, neurotoxins and enterotoxins.

Question 20

whats an cytotoxin

Answer 20

a substance (such as a toxin or antibody) having a toxic effect on cells.

Question 21

whats a neurotoxin

Answer 21

a poison which acts on the nervous system.

Question 22

whats an enterotoxin

Answer 22

a toxin produced in or affecting the intestines,

Question 23

whats an example of a cytotoxin and how does it work

Answer 23

Streptolysin which is secreted by Streptococcus pyogenes and causes beta Haemolysis of red blood cells

Question 24

what are the three types of Haemolysis and whats the odd one out

Answer 24

alpha, beta and gamma. gamma is odd one out as its actually no haemolysis

Question 25

whats an example of a neurotoxin and what does it do

Answer 25

n example of this is (Botulinum) produced by the bacteria Clostridium botulinum, this causes paralysis of muscles.

Question 26

how does a neurotoxin work

Answer 26

It interferes with muscles workability. At the NMJ synapse botulinum stops the binding of ACh vesicles to the axon terminal, so no ACh is released across the synaptic cleft.

Question 27

whats an example of an enterotoxin

Answer 27

these are associated with dysentery causing bacteria. The one we focus on is shigella dysenteries. This causing blood to release in faeces.

Question 28

what else can shigella cause

Answer 28

Not only are the receptors for these bacteria in the gut, they are also in the kidenys, so people with bad shigella end up with kidney disease.