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Bacteriology 1 > Pathogenic mechanisms > Flashcards

Pathogenic mechanisms Flashcards

1
Q

2 main host defenses (groups)

A
  • body surfaces

- defenses of tissues and blood

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2
Q

skin defenses (3)

A
  • dry, acidic pH, and low temp
  • sloughing cells
  • resident microflora
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3
Q

what does mucus contain to help with immunity (4)

A
  • secretory immunoglobulin A
  • lysozyme
  • lactoferrin
  • lactoperoxidase
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4
Q

purpose of GALT/MALT

A

produce secretory antibodies –> prevents bacterial adherence to mucosal cells

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5
Q

ways bacteria avoid killing by neutrophils (3)

A
  • resist ingesion
  • kill neutrophil
  • grow inside phagocyte
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6
Q

define: pathogens

A

disease causing microorganisms

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7
Q

define: pathogenesis

A

the physiological process involved in the generation of clinical signs of disease (means by which a pathogen causes illness)

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8
Q

define: pathogenicity

A

the capacity of a microbe to cause disease

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9
Q

define: virulence

A

ability of a microbe to cause disease efficiently (also refers to degree of pathogenicity) –> case fatality rates, ability to invade host tissues

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10
Q

define: virulence factor

A

component of a pathogen that contributes to its disease-producing potential (toxins, etc)

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11
Q

koch’s postulates

A

1) organism must always be found in humans/animals with the infectious disease but not in healthy ones
2) organism must be isolated from infected animals and grown in pure culture
3) organism isolated in pure culture must initiate disease when re-innoculated into animals
4) organism should be re-isolated from experimentally infected animals

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12
Q

what is the pathogenic capacity of an organism determined by

A

its virulence factors

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13
Q

methods by which pathogens cause disease (5)

A
  • adhesion
  • colonization
  • invasion
  • immune response inhibitors
  • toxins
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14
Q

functions of proteins produced by bacteria

A
  • colonization of parts of the body
  • disruption of cell membranes
  • stimulation of endocytosis into host cells
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15
Q

3 routes by which bacteria can penetrate gut epithelial layer

A
  • adhering to and entering M cells –> kills by apoptosis
  • adherence of fimbriae to luminal epithelial surface
  • dendrites of dendritic cells between epithelial cells to breach the layer
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16
Q

what are M cells

A

epithelial cells found on intestinal mucosa –> transport organisms and particles from gut lumen to immune cells across epithelial barrier (stimulate mucosal immunity)

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17
Q

best mechanism of adherence

A

mediated by pili or fimbriae –> mediates adherence on host cell surface

18
Q

virulence factors that promote colonization (5)

A
  • fimbriae/pili
  • adhesins
  • invasins
  • motility
  • IgA proteases
19
Q

adhesins

A
  • cell surface proteins for adherece

- mediate tighter binding of bacteria to host

20
Q

invasins

A
  • attach to host cell surface and cause changes in host cell cytoskeleton –> enter host
  • surface proteins that provoke phagocytic ingestion of bacteria by host cell
21
Q

capsule

A

covers surface of bacteria to protect it from host’s inflammatory response-complement killing activation and phagocyte-mediated killing

22
Q

how siderophores help bacterial survival

A
  • compounds that chelate iron
  • excreted into medium by bacteria
  • iron-siderophore complex taken up by bacteria
  • make iron available to bacteria (essential for growth)
23
Q

2 possibilities for bacterial invasion

A
  • immune system recognizes and destroys –> organism failed to establish itself, cannot manifest disease
  • immune system fails, organism has evolved strategy for evading/suppressing host respose
24
Q

strategies for avoiding immune system

A
  • against acquired immunity
  • against phagocytes
  • suppression of antibodies
  • antioxidant enzymes
  • spores
  • adherence mechanisms
  • toxins
25
Q

suppression of antibodies

A
  • invading organism targets immune cells
  • prevents body from mounting a response
  • ex) TB reduces IL-2
26
Q

hiding inside cells

A
  • do not present antigens that will evoke a response
  • multiply inside cells and then invade further
  • ex) brucella, listeria, TB infect macrophages
27
Q

anti-oxidant enzymes

A

deactivate products generated by phagocytes that normally kill bacteria

28
Q

anthrax spores

A
  • soil borne, persist for a long time
  • can reinfect over 70 years later
  • unique bacilli
29
Q

exotoxin

A
  • excreted by microorganism
  • can cause damage to the host by destroying cells or disrupting normal cellular metabolism
  • mostly gram +
  • released and act on the surface of host cells
30
Q

endotoxins

A
  • part of the outer membrane of the cell wall in gram - bacteria
  • not secreted (structural component only)
  • released mainly when bacteria are lysed
  • trigger phagocytes to release cytokines
31
Q

inhibition of chemotaxis

A
  • chemotaxis: process by which phagocytes are led to the site of infection
  • toxins inhibit the movement of phagocytes (staph aureus)
32
Q

inhibition of phagocytosis

A

don’t present anything for phagocytes to grip onto

33
Q

killing the phagocyte

A
  • release toxins that are lethal to phagocyte

- TB, strep, staph, anthrax

34
Q

colonization of phagocyte

A
  • allow themselves to be phagocytized but resist being killed once inside
  • multiply once inside
35
Q

indirect mechanisms of tissue damage by pathogens (3)

A
  • immune complexes (antigen:antibody complex)
  • anti-host antibody (antibody cross reacting to host)
  • cell-mediated immunity (t cells killing infected cells)
36
Q

superantigens

A
  • cause non-specific activation of t-cells –> massive cytokine release (TNF-alpha)
  • shock, multiple organ failure
37
Q

antibiotic induced infections

A
  • massive death of commensal organisms normally in the colon
  • pathogenic bacteria can take over
  • clostridium difficile
38
Q

clostridium perfringens

A
  • opportunistic pathogen
  • alpha and epsilon toxins
  • overheating disease, pulpy kidney disease
  • neurologic signs
39
Q

virulent foot rot

A
  • opportunistic pathogen
  • dissolves hoof keratin
  • spontaneous recovery
40
Q

lipopolysaccharide

A
  • LPS is integral part of gram - bacterial membrane
  • lipid A portion responsible for endotoxic activity
  • LPS activation of macrophages
41
Q

mycobacterium bovis

A
  • granulomatous lesions –> tubercles
  • inhaled or ingested
  • blocks acidification of phagolysosome
  • escapes phagolysosomes to replicate within host cells
  • impaired organ function
42
Q

mycobacterium paratuberculosis

A
  • johne’s disease
  • infected feces ingestion
  • enteric disease

Bacteriology 1 (10 decks)

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