6.1 virulence factors

Question 1

the normal human microbiota composed of

Answer 1

composed of bacterial, fungal, some viral species acquired at birth.

Question 2

normal human microbiome changes..

Answer 2

over lifetime

Question 3

normal human microbiome found on

Answer 3

external and internal tissues,

Question 4

normal human microbiomes form

Answer 4

biofilms by adhering to surface of tissues and to one another

Question 5

the normal human microbiota can turn on us.. some bacteria can become opportunistic pathogens..

Answer 5

if introduced to an unusual site, when the body is immunosuppressed, and when antimicrobial agents disrupt the normal balance of microbes

Question 6

example of when bacteria become opportunistic pathogens if introduced to an unusual site (organisms)

Answer 6

Staphylococcus aureus, E. coli

Question 7

example of when bacteria become opportunistic pathogens when the body is immunosuppressed

Answer 7

pseudomonas species in cystic fibrosis lung

Question 8

example of when bacteria become opportunistic pathogens when antimicrobial agents disrupt the normal balance of microbes

Answer 8

clostridium difficile in GI tract

Question 9

Or pathogenic bacteria can be..,

Answer 9

acquired from the environment

Question 10

infection - definition

Answer 10

the invasion and multiplication of microorganisms (bacteria, viruses) that are not normall present within the body.

Question 11

patogen - definition

Answer 11

microbial parasite

Question 12

pathogenicity - definition

Answer 12

the ability of a parasite to inflict damage on the host.
– some pathogens kill cell instantly, others remain on host cell for a while..

Question 13

virulence - definition

Answer 13

measure of pathogenicity - relative ability of a pathogen to cause disease

Question 14

opportunistic pathogen - definition

Answer 14

causes disease only in the absence of normal host resistance

Question 15

virulence factors - definition

Answer 15

any of the pathogens genetic, biochemical, or structural features that enable it to produce a disease in a host.

Question 16

examples of virulence factors (think part of bacteria as well as other things)

Answer 16

plii, capsules, flagella
– bacterial proteases and mimicry.

Question 17

bacterial proteases examples

Answer 17

these are enzymes synthesized by bacteria that function to cleave host proteins – inactivating them

Question 18

mimicry examples

Answer 18

bacteria modify themselves and appear like they belong in the host – allows themselves to evade the defense mechanisms of the host cell by blending in

Question 19

are normal flora bacterial pathogens?

Answer 19

typically no, but if those bacteria get to places in the body where they dont belong, then they will cause problems

Question 20

example of opportunistic bacteria from normal flora

Answer 20

if a person has an injury to the gut that causes rupture, then bacteria that are normally in intestine will escape to bloodstream – they are in a new niche, therefore can proliferate and cause disease.

Question 21

who is Robert Koch known as

Answer 21

grandfather of microbiology

Question 22

what did Koch win a nobel prie for

Answer 22

discoveries in relation to TB

Question 23

what are the bacteria Koch worked with

Answer 23

Mycobacterium tuberculosis, vibrio cholerae, Bacillus anthracis

Question 24

what was Koch’s postulates designed for

Answer 24

an attempt to establish a standard for identifying specific causes of infectious diseases.

Question 25

step 1 Kochs postulates

Answer 25

1. the suspected causative agent must be found in every case of disease, and absent from healthy hosts

Question 26

step 2 kochs postulates

Answer 26

agent must be isolated and grown inside the host

Question 27

step 3 kochs postulates

Answer 27

when the agent is introduced to a healthy, susceptible host, the host must get the disease.

Question 28

step 4 kochs postulates

Answer 28

same agent must be reisolated from the diseased experimental host

Question 29

Molecular kochs postulates basic three steps/indicators

Answer 29

1. a gene must be linked to the disease in an animal 2. removal/mutation of the gene results in loss or reduction of virulence. 3. returning the gene into the organism restores full virulence.

Question 30

the three classes of the 'traditional' virulence factors

Answer 30

endotoxins, extracellular enzymes, and exotoxins

Question 31

endotoxins

Answer 31

bacterial products that typically have functions for the bacterial survival, but also results in diseased condition for infected host.

Question 32

examples of endotoxins

Answer 32

Lipid A (LPS), Lipoteichoic Acid

Question 33

extracellular enzymes

Answer 33

function outside the bacterial cell to damage non-specific host cells/tissues - enzymes secreted by bacteria

Question 34

exotoxins

Answer 34

proteins that are secreted into the environment from pathogen cell as it grows - can have activity EVEN in the absence of the pathogenic bacteria

Question 35

endotoxin - Lipid A

Answer 35

- not actively secreted from the bacterial cell - normally present on cell and required for bacterial survival - if sensed by host and at elevated levels, can lead to excessive inflammation, fever - effects more acute with higher # of cells

Question 36

extracellular enzymes examples

Answer 36

hyaluronidase, collagenase

Question 37

what is hyaluronidase secreted by

Answer 37

clostridium perfringens

Question 38

what does hyaluronidase do

Answer 38

targets and degrades cell surface molecules -- allows pathogens to pass through -- attacks specific host molecules (proteins and lipids) -- promote colonization of bacteria.

Question 39

what are collagenase secreted by

Answer 39

clostridium perfringens

Question 40

what do collagenase do

Answer 40

targets and degrades cell surface molecules as well - degrades collagen between endothelial cells, allowing bacteria to enter bloodstream

Question 41

exotoxins have three classes, what are they

Answer 41

intracellular targeting toxins, membrane disrupting toxins, and superantigen toxins

Question 42

intracellular targeting toxins, two types

Answer 42

AB toxins and AB5 toxins

Question 43

AB toxin - intracellular targeting process

Answer 43

-- B component binds to the host cell through interaction with specific cell surface receptors -- entire toxin is brought into host cell through endocytosis -- once inside the vacuole, A component separates from B compound, and A component gains access to the cytoplasm where it exhibits its toxin effects.

Question 44

what is an example of an AB toxin

Answer 44

Diptheria toxin

Question 45

what is the mechanism of diptheria toxin

Answer 45

- B subunit attached to vacuole membrane - A subunit in cytoplasm where it inactivates elongation factor 2 by transferring an ADP-ribose onto that protein - this stops protein synthesis and kills the cell

Question 46

examples of AB5 toxins

Answer 46

shiga toxin (E. coli O157:H7) cholera (Vibrio cholerae) botox (Clostridium botulinim)

Question 47

A and B meaning in AB5 toxin

Answer 47

A = active B = binding -- pentamer -- all B components are identical

Question 48

AB5 toxin mechanism of action (Cholera toxin)

Answer 48

- B subunits bind to intestinal enterocytes on GM1 receptor - entire toxin is internalized through endocytosis - trafficked through golgi and ER - A subunit is cleaved and released - A1 causes hyperactivation of adenylyl cyclase, resulting in elevated levels of cAMP. - increase cAMP causes secretion of salt and fluid through the channel CFTR

Question 49

example of a membrane disrupting (pore forming) toxin

Answer 49

Staphylococcus aureus alpha toxin

Question 50

mechanism of action of membrane disrupting alpha toxin

Answer 50

pore formation of the plasma membrane by this toxin degrades the membrane integrity, and leads to uncontrolled flux of ions and water, causing cell death

Question 51

Staphylococcus aureus a-toxin is a..

Answer 51

hemolysin

Question 52

example of superantigen

Answer 52

Toxic shock syndrome toxin 1

Question 53

mechanism of action of toxic shock syndrome

Answer 53

areas with absorbant substances (tampons) provide optimal environment for proliferation of staphylococci -- favours production of TSST-1 - this superantigen is secreted into the bloodstream and increases cytokines `

Question 54

how does the toxic shock syndrom toxin 1 increase number of cytokines

Answer 54

TSST 1 binds to macrophages and to CD4 lymphocytes, which stimulates the production of cytokines -- leads to fever, rash, hypertension