Lecture 33 - What Makes a Bacterium Pathogenic

Question 1

Which is NOT an immune component encountered by a bacterium upon first exposure?

a. IgM
b. Mucus
c. Neutrophil
d. Macrophage

Answer 1

c. neutrophil

Question 2

Which bacterium is acid-fast?

a. E. coli
b. bacillus
c. mycoplasma
d. mycobacterium

Answer 2

d. mycobacterium

Question 3

Which bacterium is perfectly happy at 4 degrees Celsius?

a. E. coli
b. Listeria
c. Leptospira
d. salmonella

Answer 3

b. listeria

Question 4

which is the MOST common leukocyte in an abscess?

Answer 4

neutrophil

Question 5

self-replicating genes in bacteria are called

Answer 5

plasmids

Question 6

which is an example of a slow-growing bacterium

a. leptospira spp.
b. escherichia coli
c. listeria monocytogenes
d. mycobacterium tuberculosis

Answer 6

d. mycobacterium tuberculosis

Question 7

parasite

Answer 7

an organism that lives in association with and at the expense of an animal host

Question 8

primary pathogen

Answer 8

a microbe that WILL cause disease if exposed

Question 9

opportunistic pathogen

Answer 9

an organism that CAN cause disease under certain circumstances

Question 10

saprophyte

Answer 10

organism that normally inhabits inanimate environments shared with animals

Question 11

commensal

Answer 11

organisms that do not cause harm to the host

Question 12

what are the first innate immune defenses that a microbe encounters?

Answer 12

1. mucus, sebum, tears
2. low/high pH
3. mucociliary escalator
4. IgA, complement
5. epithelial barrier
6. sentinel cells (mast, macro -, and dendritic)

Question 13

Pathogenicity

Answer 13

ability to cause disease

Question 14

Virulence

Answer 14

degree of pathogenicity, clinical signs

Question 15

Virulence factor

Answer 15

products produced by the pathogen that facilitates pathogenesis

Question 16

host

Answer 16

animal affected

Question 17

host-specificity

Answer 17

range of species that can be infected and affected by the pathogen

Question 18

what were Koch’s postulates?

Answer 18

1. present in all cases
2. agent isolated and propagated outside the host
3. produces original disease in host
4. re-isolated from experimental infection

Question 19

Virulence factors are either _____ or _____

Answer 19

synthesized; structural

Question 20

what do virulence factors allow for?

Answer 20

1. colonization (adhesins)
2. invasion (invasins)
3. evasion
4. suppression
5. acquisition of nutrients

Question 21

pathogenicity islands

Answer 21

clusters of genes that code for virulence determinates

Question 22

virulence plasmids

Answer 22

clusters of self-replicating extrachromosomal genes encoding virulence

Question 23

what are the 7 steps in pathogenicity

Answer 23

1. exposure
2. adhesion
3. colonization
4. invasion
5. evasion of host defenses
6. damage to host tissue
7. +/- transmission

Question 24

what are the main modes of exposure

Answer 24

1. ingestion
2. inhalation
3. inoculation

Question 25

what are adhesins? give examples

Answer 25

proteins on the surface that help with attachment fimbrial proteins or pili

Question 26

what are host receptors that bacteria attach to

Answer 26

fibronectin sialic acid

Question 27

how do commensal bacteria keep pathogenic bacteria from attaching

Answer 27

they block receptor sites and secrete toxic substances that prevent pathogens from colonizing

Question 28

Describe enterotoxigenic e. coli

Answer 28

- diarrhea in young animals/people/travelers - bind receptors in the mucus layer via fimbrial attachment - secrete heat labile and stable enterotoxins that disrupt cell membrane transport - disrupt chloride channels

Question 29

What are invasins responsible for

Answer 29

cytoskeletal arrangements

Question 30

describe the "zipper" mechanism

Answer 30

1. infection - bacteria w adhesin finds target cell 2. receptor binding - adhesion binds to surface cell receptors 3. membrane engulfment 4. endosomal trafficking

Question 31

describe the "trigger" mechanism

Answer 31

1. infection - bacteria w T3SS finds target cell 2. effector injection - T3SS punctures the target cell 3. membrane ruffling 4. endosomal trafficking

Question 32

Describe enterohemorrhagic E. coli pathogenesis

Answer 32

- carried by cattle - invasin called intimin - attaching and effacing lesions cause bloody diarrhea - humans are more susceptible to shiga toxin

Question 33

A bacterium that do not normally cause disease in or help its host is called a

Answer 33

commensal

Question 34

A bacterial PRODUCT that generally causes disease in the host is called a

Answer 34

virulence factor

Question 35

Adhesions can be found on

Answer 35

pili

Question 36

what are the 4 mechanisms of spread

Answer 36

1. direct 2. lymphatic/blood 3. organ architecture (bronchial tree, bile ducts, nerves) 4. within phagocytes

Question 37

describe Burkholderia mallei pathogenesis

Answer 37

- gram-negative, aerobic, facultative intracellular rods - primary lesion in upper airways/skin - spread via lymphatic within macrophages

Question 38

what are the 6 host defense evasion mechanisms

Answer 38

1. firm attachment 2. prevention of mechanical removal 3. avoidance of phagocytosis 4. impairment of phagocytic function 5. degradation of antibodies/complement 6. alteration of blood supply

Question 39

how do bacteria prevent phagocytic degradation

Answer 39

- make toxins/proteins that kill phagocytes - block opsonins - produce capsule that "hides" microbe - inhibit fusion of microbe-containing phagosomes w/ lysosomes - help escape into the cytoplasm - antioxidants block phagolysosomal killing

Question 40

describe mycobacterium tuberculosis pathogenesis

Answer 40

- host-adapted and slow-growing - phagocytized but prevents phagolysosomal generation - can reactivate

Question 41

describe listeria pathogenesis

Answer 41

- Gram-positive, facultatively intracellular rod - foodborne pathogen - grows at cooler temps - can be transmitted by peripheral nerve endings to the CNS - can translocate the intestine, use ActA to polymerize host actin and avoid immune response

Question 42

what is contained in abscesses

Answer 42

neutrophil, extracellular bacteria

Question 43

what enzyme is responsible for the production of pus-like liquid

Answer 43

myeloperoxidase

Question 44

Describe staphylococcus pathogenesis

Answer 44

- gram-positive, "grape-like" clusters, facultative anaerobes - common on skin and mucus membranes - penicillin resistance common - methicillin-resistant (MRSA) common to hospitals

Question 45

what is a granuloma

Answer 45

focal aggregate of large, epitheliod macrophages

Question 46

what type of bacteria causes granulomas

Answer 46

intracellular; mycobacterium

Question 47

Describe the pathogenesis of Johne's Disease

Answer 47

- mycobacterium - a chronic, contagious disease in ruminants that affects the small intestine - lamina propria of villi expanded due to macrophages

Question 48

what is a biofilm

Answer 48

self-produced matrix of an extracellular polymeric substance

Question 49

which mechanism of immune evasion does Mycobacterium tuberculosis use

Answer 49

phagosomal maturation inhibition

Question 50

how does listeria spread from cell to cell while AVOIDING the immune response

Answer 50

polymerizing host actin

Question 51

what is the most concerning characteristic of biofilms

Answer 51

bacteria can exchange antibiotic resistance genes