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MBIO > medical microbio: pathogenesis > Flashcards

medical microbio: pathogenesis Flashcards

1
Q

infection

A

growth of microbes that are not normally present in the host (regardless of whether or not the host is harmed)

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2
Q

disease

A

damage or injury that impairs regular host functions

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3
Q

pathogen

A

a microbe that is able to cause disease

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4
Q

opportunistic pathogen

A

a microbe that causes disease only in the absence of normal host resistance:

ex. streptococcus pneumoniae- causes pneumonia in immunocompromised patients
ex. e.coli-causes urinary tract infections when bacteria from feces are moved into the urethra

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5
Q

pathogenicity

A

the ability to cause disease

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6
Q

virulence

A

the severity of the disease that is caused

  • often given as an LD50 value
  • number of cells of a pathogen (or dose of a toxin) that will cause death in 50% of infected animals
    ex. streptococcus pneumoniae - LD50 ~50 cells
    ex. salmonella enterica- LD~5000 cells
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7
Q

pathogenesis

A

the precess by which a disease develops

*steps that lead to an infection and tissue damage

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8
Q

virulence factors

A

genetically encoded traits that contribute to a pathogen’s ability to cause disease

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9
Q

adherence

A

the ability of a pathogen to stick to a surface and begin colonization

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10
Q

non-covalent adherence factors

A

ex. capsules and slime layers
- streptococcus mutans uses slime layer to stick to teeth and form a biofilm
- streptococcus pneumoniae uses capsule to stick to cells in the lungs
- also protects the cell from phagocytes

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11
Q

other adherence factors

A

-adhesins- specific surface molecules that allow selective adherence to particular cell types

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12
Q

examples of adhesins

A
  • strains of enterotoxigenic E.coli produce fimbriae and can adhere specifically to cells in teh small intestine
  • Neisseria gonorrhoeae produces fimbriae that allow it to attach to mucosal epithelial cells
  • retract to bring bacteria close to the membrane
  • opa proteins then specially attach to certain receptors on the host cell
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13
Q

some pathogens can colonize and grow on the surface of tissues others need to _______

A

invade tissue

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14
Q

invasiveness

A

-the ability of a pathogen to enter into host cells or spread through tissues

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15
Q

virulence factors that promote invasiveness

A
  • siderophores
  • exoenxymes
  • invasins
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16
Q

siderophores

A

iron binding molecules

  • host proteins transferrin and lactoferrin- sequester iron, making it unavailable for microoganisms
  • limits the growth of invaders
  • siderophores rip iron out of tissues to be used by bacteria
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17
Q

exoenzymes

A
  • excreted by bacteria to degrade host tissues
  • hyaluronidase
  • collagenase
  • proteases, nucleases and lipases
  • fribrinolysin
  • coagulase
18
Q

hyaluronidase

A

hydrolyzes hyaluronic acid (cement that holds animal cells together)

19
Q

collagenase

A 
degrades collagen (structural component of connective tissue)
allows pathogen to spread through tissues
20
Q

proteases, nucleases and lipases

A

degrade host macromolecules

21
Q

fibrinolysin

A

dissolves fibrin clots

*ex. streptococcus pyogenes makes streptokinase

22
Q

coagulase

A

induces fibrin clots

ex. staphlococcus aureus produces coagulase to protect it from phagocytes
* keeps staph infections localized

23
Q

invasins

A

proteins that allow bacteria to invade and enter directly into host cells

24
Q

listeria monocytogenes

A
  • invasins
  • non lactic acid, non pore forming psychrotolerant (grows best at lowe temp) member of the firmicutes
  • produces invasins that promote phagocytosis by macrophages
  • hijacks the cytoskeleton to escape the phagolysosome
  • spreads from cell to cell- avoiding humoral immune response
25
Q

some pathogens remain localized at the site of infection while others _____

A

spread

26
Q

bacteremia

A

bacteria in the blood

can be carried to different organs and tissues

27
Q

septicemia

A

bacteria multiplying in the blood (blood borne systemic infection)
-can lead to sepsis

28
Q

sepsis

A

widespread systemic inflammation

29
Q

septic shock

A

can be caused by gram negative bacteria (gram negative sepsis)
-also by gram positives : staphylococci and enterococci

30
Q

exotoxins

A

proteins released by growing bacteria

  • inhibit host cell function (or kill host cells)
  • usually heat labile
  • can be extremely toxic
31
Q

bacillus anthracis

A
  • exotoxins
  • several virulence factors: capsule, exoenzymes and the anthrax toxin
  • interferes with the immune response and kills macrophages
32
Q

there are three categories of exotoxins

A

cytoxins
AB toxins
superantigens

33
Q

cytotoxins

A 
disrupt cytoplasmic membrane integrity 
cell lysis and death 
-hemolysins
-lecithinase or phospholipase 
-leukocidins
34
Q

hemolysins

A

lyse many cells (not just red blood cells)

ex. streptococcus pyogenes
- produces streptolysin sterols in the cell membrane

35
Q

lecithinase or phospholipase

A

dissolves membrane lipids

  • ex. clostridium perfringens
  • alpha-toxin (gas gangrene)
36
Q

leukocidins

A

destroy white blood cells
ex. staphylcoccus aureus - staphylococcal alpha-toxin
toxin subunits insert into the membrane and oligomerize to form a heptamer
a membrane spanning pore
cell contents leak out and the cell dies

37
Q

AB toxins

A

two subunits : active subunit and binding subunit
ex.diphtheria toxin (corynebacterium diphtheriae)
subunit B- specifically binds to a protein on animal cells
subunit A- then moves across the membrane
*interferes with protein synthesis
-gene for diphtheria toxin is not encoded on the chromosome, but instead on a virus

38
Q

other AB toxins

A

tetanus, botulism and cholera toxins

39
Q

superantigens

A
  • activate T cells to elicit an extreme immune response
  • bind to MHC molecules and TCRs outside the antigen bind sites
  • bridge the gap and mimics proper antigen presentation
  • huge number of T cells can be activated
  • T cells produce cytokines
  • extreme immune response
  • extreme fever, systemic inflammation, shock, death
    ex. staphylococcus aureus’s toxic shock syndrome toxin
40
Q

endotoxins

A

lipopolysaccharide from the gram negative outer membrane

  • toxic part is lipid A -only released when the cells die
  • generally considered less toxic than exotoxins (need a lot to cause symptoms)
41
Q

salmonellosis

A

food borne illness
endotoxin
-salmonella colonizes the intestine-multiply to a huge number of bacteria
*as those bacteria die, they release endotoxin
*fever, diarrhea, generalized inflammation

42
Q

gram negative species

A

endotoxins

  • gram negative bacteria multiply in the blood
  • killed by immune system, releasing endotoxin
  • massive inflammation leads to septic shock an death

MBIO (9 decks)

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