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Animal Health & Disease 1 > Lecture 33 - What Makes a Bacterium Pathogenic > Flashcards

Lecture 33 - What Makes a Bacterium Pathogenic Flashcards

1
Q

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

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

A

c. neutrophil

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2
Q

Which bacterium is acid-fast?

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

A

d. mycobacterium

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3
Q

Which bacterium is perfectly happy at 4 degrees Celsius?

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

A

b. listeria

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4
Q

which is the MOST common leukocyte in an abscess?

A

neutrophil

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5
Q

self-replicating genes in bacteria are called

A

plasmids

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6
Q

which is an example of a slow-growing bacterium

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

A

d. mycobacterium tuberculosis

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7
Q

parasite

A

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

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8
Q

primary pathogen

A

a microbe that WILL cause disease if exposed

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9
Q

opportunistic pathogen

A

an organism that CAN cause disease under certain circumstances

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10
Q

saprophyte

A

organism that normally inhabits inanimate environments shared with animals

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11
Q

commensal

A

organisms that do not cause harm to the host

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12
Q

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

A
  1. mucus, sebum, tears
  2. low/high pH
  3. mucociliary escalator
  4. IgA, complement
  5. epithelial barrier
  6. sentinel cells (mast, macro -, and dendritic)
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13
Q

Pathogenicity

A

ability to cause disease

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14
Q

Virulence

A

degree of pathogenicity, clinical signs

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15
Q

Virulence factor

A

products produced by the pathogen that facilitates pathogenesis

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16
Q

host

A

animal affected

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17
Q

host-specificity

A

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

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18
Q

what were Koch’s postulates?

A
  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
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19
Q

Virulence factors are either _____ or _____

A

synthesized; structural

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20
Q

what do virulence factors allow for?

A
  1. colonization (adhesins)
  2. invasion (invasins)
  3. evasion
  4. suppression
  5. acquisition of nutrients
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21
Q

pathogenicity islands

A

clusters of genes that code for virulence determinates

22
Q

virulence plasmids

A

clusters of self-replicating extrachromosomal genes encoding virulence

23
Q

what are the 7 steps in pathogenicity

A
  1. exposure
  2. adhesion
  3. colonization
  4. invasion
  5. evasion of host defenses
  6. damage to host tissue
  7. +/- transmission
24
Q

what are the main modes of exposure

A
  1. ingestion
  2. inhalation
  3. inoculation
25
Q

what are adhesins? give examples

A

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

26
Q

what are host receptors that bacteria attach to

A

fibronectin
sialic acid

27
Q

how do commensal bacteria keep pathogenic bacteria from attaching

A

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

28
Q

Describe enterotoxigenic e. coli

A
  • 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
29
Q

What are invasins responsible for

A

cytoskeletal arrangements

30
Q

describe the “zipper” mechanism

A
  1. infection - bacteria w adhesin finds target cell
  2. receptor binding - adhesion binds to surface cell receptors
  3. membrane engulfment
  4. endosomal trafficking
31
Q

describe the “trigger” mechanism

A
  1. infection - bacteria w T3SS finds target cell
  2. effector injection - T3SS punctures the target cell
  3. membrane ruffling
  4. endosomal trafficking
32
Q

Describe enterohemorrhagic E. coli pathogenesis

A
  • carried by cattle
  • invasin called intimin
  • attaching and effacing lesions cause bloody diarrhea
  • humans are more susceptible to shiga toxin
33
Q

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

A

commensal

34
Q

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

A

virulence factor

35
Q

Adhesions can be found on

A

pili

36
Q

what are the 4 mechanisms of spread

A
  1. direct
  2. lymphatic/blood
  3. organ architecture (bronchial tree, bile ducts, nerves)
  4. within phagocytes
37
Q

describe Burkholderia mallei pathogenesis

A
  • gram-negative, aerobic, facultative intracellular rods
  • primary lesion in upper airways/skin
  • spread via lymphatic within macrophages
38
Q

what are the 6 host defense evasion mechanisms

A
  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
39
Q

how do bacteria prevent phagocytic degradation

A
  • 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
40
Q

describe mycobacterium tuberculosis pathogenesis

A
  • host-adapted and slow-growing
  • phagocytized but prevents phagolysosomal generation
  • can reactivate
41
Q

describe listeria pathogenesis

A
  • 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
42
Q

what is contained in abscesses

A

neutrophil, extracellular bacteria

43
Q

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

A

myeloperoxidase

44
Q

Describe staphylococcus pathogenesis

A
  • gram-positive, “grape-like” clusters, facultative anaerobes
  • common on skin and mucus membranes
  • penicillin resistance common
  • methicillin-resistant (MRSA) common to hospitals
45
Q

what is a granuloma

A

focal aggregate of large, epitheliod macrophages

46
Q

what type of bacteria causes granulomas

A

intracellular; mycobacterium

47
Q

Describe the pathogenesis of Johne’s Disease

A
  • mycobacterium
  • a chronic, contagious disease in ruminants that affects the small intestine
  • lamina propria of villi expanded due to macrophages
48
Q

what is a biofilm

A

self-produced matrix of an extracellular polymeric substance

49
Q

which mechanism of immune evasion does Mycobacterium tuberculosis use

A

phagosomal maturation inhibition

50
Q

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

A

polymerizing host actin

51
Q

what is the most concerning characteristic of biofilms

A

bacteria can exchange antibiotic resistance genes

Animal Health & Disease 1 (52 decks)

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