Invasive gram negative pathogens of GI tract Flashcards

1
Q

what are the 3 mechanisms bacteria can use to cause infections

A

1 - invade the mucous membrane
2 - toxin producers
3 - hybrid of the two above

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2
Q

what are the 2 main gram (-) bacterial species that cause infections by invasion of the mucous membrane

A

salmonella and shigella

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3
Q

shigella species of gram negative pathogens has 4 subgroups distinguished by what antigen

A

O antigen (based on structure of LPS

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4
Q

what is RpoS ?

A

transcription factor that causes acid resistance in shigella allowing pathogen to pass through stomach

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5
Q

which gram negative bacteria has a small inoculum size ? large ?

A

shigella is small, salmonella is large

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6
Q

explain how shigella pathogens invade humans

A

1 - enter host M cells for transport to basal surface
2-released at lamina propria and ate by macrophages causing inflammatory response
3- pathogens not eaten ingested by epithelial cells and put in vesicle
4-shigella proteins lyse the vesicle
5- spread locally intracellulary via IcsA

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7
Q

which is resistant to pathogen infection in humans, the mucous surface or basal surface

A

basal surface

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8
Q

what do shigella pathogens produce to signal human M cells to pick them up for transport to basal surface

A

shigella pathogens have proteins called “invasion plasmid antigens”

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9
Q

what is IcsA

A

protein ATPase of shigella causing polymerization of actin which pushes shigella cells into adjacent epithelial cells w/o going into cytoplasm and getting destroyed by immune system

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10
Q

is shigella a localized infection or systemic ? why ?

A

localized because just stays in epithelial cells and away from blood stream

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11
Q

what develops when the invaded epithelial cells die off from shigella infection

A

ulcer

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12
Q

what specific subgroup of shigella induces a watery diarhea stool

A

shigella sonnei (most common)

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13
Q

what specific type of shigella produces the Shiga toxin and is the most severe of shigella diseases

A

Shigella dysenteria type 1

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14
Q

what does the Shiga toxin in shigela dysenteria cause

A
  • kills intestinal epithelial and endothelial cells=more diarhea
  • dirsupts Na absortion
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15
Q

Salmonella pathogen can cause what 2 diseases

A

1- Gastroenteritis

2-Typhoid fever

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16
Q

how is salmonella transmitted to humans

A

fecal (human or animal) to mouth

17
Q

Is salmonella acid resistant or not ?

A

Not as acid resistant as shigella

18
Q

if salmonella pathogens survive through the low acidity of the stomach, the low pH will induce what ?

A

pathogenicity islands on large virulence proteins

aka - virulence proteins

19
Q

how does salmonella pathogen invade the human

A

1-approach cell mucosal surface and increase Ca levels
2-induces surface “ruffles” and uptake of pathogens into vesicles
3-remain in vesicles for hours
4 - released into lamina propria and induces Na and Cl loss causing diarhrea
5 - Macrophages eat or if escape become transient

20
Q

how is salmonella typhi, which causes typhoid fever, different from normal salmonella species

A

it is not killed by macrophages, these survive and grow/replicate inside macrophages then enter lymphatic system becoming system (much more severe)

21
Q

T/F Salmonella typhi has an animal resovoir

A

F, it is strictly a human pathogen

22
Q

Who is typhoid mary and explain her situation

A

she was a carrier of salmonella typhi w/o knowing

23
Q

where in the body do salmonella typhi carriers have colonized pathogens

A

gall bladders

24
Q

how do you diagnose what species of invasive pathogens are causing a disease

A

stool cultures

25
Q

how do you treat enteric/GI diseases

A

antibiotics

26
Q

which pathogen invades the mucous membrane by altering the hosts ion signalling pathways ?

A

salmonella