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ABBEY MSII U6 > Micro Enteric Bacteria 1 > Flashcards

Micro Enteric Bacteria 1 Flashcards

1
Q

shigella bacteriology

A
  • gram -, oxidase - rods
  • not lactose fermenting
  • not H2S producing
  • nonmotile
  • facultative anaerobes and facultative intracellular
  • human-restricted
  • fecal-oral
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2
Q

how to distinguish lactose fermenter from non lactose fermenter

A

MacConkey medium - fermenters will be bright pink

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3
Q

shigella infectious dose

A

very low ~100IUs

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4
Q

what does shigella typically cause?

A

bloody diarrhea, local inflammation, ulceration

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5
Q

what complications are there a risk for with shigella?

A
  1. reactive arthritis (Reiter’s Syndrome - can’t pee, can’t see, can’t climb a tree)
  2. HUS
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6
Q

what is a sign of a poorer prognosis with shigella?

A

malnourished child (esp with vit A and zinc deficiencies)

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7
Q

Reactive arthritis autoimmune?

A

HLA-B27

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8
Q

shigella virulence factors

A
  1. shiga toxin - plasmid borne
    - toxin causes cell necrosis, apoptosis, inflammatory response, and hemorrhage for bloody diarrhea
  2. siderophores
  3. type III secretion system
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9
Q

siderophores

A

iron-chelating moles that allow the bacteria to parasitize enough iron to grow to large numbers

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10
Q

how does shigella invade?

A

enters through M cells and infects macrophages - goes into epithelial cells backwards and sideways to infect neighboring cells causing a local infection

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11
Q

how is entry of shigella mediated?

A

type III secretory system

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12
Q

how does shigella cause HUS?

A

shiga toxin escapes into blood stream setting off an immunologic/hematologic cascade leading to acute hemolysis, uremia, DIC

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13
Q

diagnosis of shigella

A

physical: fever, dehydration, severe headache, progression from watery to bloody diarrhea
lab: agglutination, methylene blue (neutrophils) stain of fecal matter
* *usually affects very old or very young

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14
Q

diagnosis of HUS caused by shigella or E. coli

A

check blood for schistocytes, decreased platelets, increased PMNs, increased lactate dehydrogenase

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15
Q

shigella treatment

A

rehydrate, antibiotics if warranted but NOT if suspecting E Coli!!!, HUS dialysis and supportive care, NO antidiarrheal meds

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16
Q

e coli bacteriology

A
  • straight gram - rod
  • facultative anaerobe
  • lactose fermenter
  • H2S negative, urease negative
  • may be mobile or nonmobile
  • normal GI fauna
17
Q

e coli pathologies

A
  1. enterotoxigenic diarrhea
  2. enterohemorrhage diarrhea
  3. enteropathogenic, enteroaggregative, enteroinvasive diarrheas
  4. UTIs
  5. meningitis
  6. pneumonia
18
Q

is E coli intracellular or extracellular?

A

EXTRACELLULAR (have fimbriae for adherence or Type III or IV secretion system) with the exception of EIEC which is like shigella with actin-based cell to cell motility

19
Q

e coli gastroenteritis

A
  • water diarrhea
  • bacteria use fimbrae to attach to gut lining
  • enterotoxins force hot cells to release fluids, potassium
20
Q

e coli bloody gastroenteritis

A
  • bloody diarrhea
  • bacteria adhere to gut lining with some tissue destruction
  • strains carrying Shiga plasmid which becomes active inside gut cells, shutting down protein synthesis, destroying some, and causing inflammation
  • if toxin reaches bloodstream, risk of HUS
21
Q

risk of HUS

A

shiga toxin in EHEC

22
Q

Enterohemorrhagic E coli (EHEC) pathogenesis

A

includes O157:H7 - carries shiga toxin gene which halts host protein synthesis and kills infected cells causing a bloody diarrhea with 9-30% proceeding to HUS (acute renal failure, microangiopathic hemolytic anemia and thrombocytopenis)

23
Q

what is EHEC associated with?

A

antibiotics to treat bloody diarrhea

24
Q

what happens when shiga toxin hits the bloodstream?

A

Gb2 receptor activated, nephrotoxicity, capillary occlusion (fibrin-platelet thrombi in renal microvasculature), cytokine dysreguation (esp vWF, TNFalpha, IL1, IL6), kidney failure with lactate dehydrogenase marker

25
Q

diagnosis e coli

A

pink on MacConkeys (lactose fermenter), bloody or nonbloody diarrhea, dehydration, recent travel abroad
check for HUS

26
Q

e coli treatment

A

self-limited, rehydrate

EHEC: give NO antimotility agents and antibiotics associated with increased HUS risk

27
Q

staph aureus food poisoning

A

gastroenteritis caused by toxin secreted by staph aureus in room temp food
-onset is fast - intoxication process only takes hours (infectious process would take at least a day)

28
Q

foodborne botulism

A

gastroenteritis and descending flaccid paralysis caused by neurotoxin secreted by clostridium botulinum into airtight-packed food
-onset is fast (not as fast as staph)

ABBEY MSII U6 (18 decks)

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