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Microm 442 > Lecture 19 Pathogenic shigella and E coli > Flashcards

Lecture 19 Pathogenic shigella and E coli Flashcards

1
Q

What species are part of your normal flora of your stomach?

A
  • E. coli non-pathogenic species
  • Klebsiella
  • Enterobacter
  • Proteus
  • Serratia
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2
Q

What is not part of the human flora?

A
  • Salmonella
  • Shigella
  • Yer sinia
  • Pathogenic E. coli
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3
Q

What type of diseases are caused by bacteria not part of the human flora.

A

•Cause a wide variety of disease •endotoxic shock, UTI, diarrhea, HUS

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4
Q

How is E. Coli identified,

A
  • Gram negative
  • Lactose fermentation.
  • indole positive
  • most are normal colonic flora
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5
Q

What are the type of diseases caused by E. coli?

A
  • Urinary Tract Infection (UTI)
  • Gastroenteritis
  • Septicemia - usually following UTI or gastroenteritis
  • Neonatal meningitis
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6
Q

What E. Coli infections are not caused by a person’s own flora?

A

gastroenteritis and neonatal meningitis

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7
Q

What plates can be used to identify E. Coli?

A
  • CHROMagar

- MacConkey

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8
Q

What is unique about CHROMagar?

A

Has a unique specific metabolism for multiple organisms, can grow multiple organism on plate and identify the different types.

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9
Q

What is a common theme between pathogenic E. Coli?

A

-secretion and new DNA. Not normal flora. Uses different mechs to cause disease.

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10
Q

What are the surface structures of E. Coli?

A
  • O antigen
  • H antigen (flagella)
  • BFP pili
  • CFA pili
  • Type 1 pili
  • K antigen capsule
  • P pili
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11
Q

What are BFP pili?

A

bundle forming pili: found in EPEC strains

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12
Q

What is CFA pili?

A

colonization factor antigen: pili used by ETEC strains for binding to host cells

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13
Q

What are type 1 pili?

A

common pili binds via FimA to mannose residues on epithelial cells

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14
Q

How does EPEC cause diarrheal disease?

A

BFP used to form cluster of cells, injects effector proteins, causes pedestal formation.

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15
Q

How does EHEC cause diarrhea?

A

causes pedestal formation and injects Stx-shiga toxin into the cells.

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16
Q

How does EHEC cause disease?

A

uses CFA pili to bind then secretes two types of enterotoxins: ST (heat stable) and LT (heat labile).

17
Q

How does EAEC cause disease?

A

forms a biofilm on the surface of the cells, produces cytotoxins and enterotoxins to cause diarrhea.

18
Q

How does EIEC cause diarrhea?

A

binds, then invades cells, then escapes into the cytoplasm. Similar to Shigella.

19
Q

How does DAEC cause diarrhea?

A

binds as single cells.

20
Q

What is UPEC E. Coli?

A
  • Uropathogenic E.coli:
  • causes most cases of Pyelonephritis (kidney infection)
  • infection starts from spreading to colon to bladder
21
Q

What makes UPEC so good at causing infection?

A

-P pili and FimH

22
Q

What are some characteristics of ETEC?

A
  • prevalent in developing world (traveler’s diarrhea and infantile diarrhea
  • spread via food
  • attacks small bowel causing watery diarrhea
  • no histological or inflammatory changes to GI tract.
  • treatment is hydration
23
Q

What are the toxins produced by ETEC?

A
  • LT - Heat Liable (similar to cholera) .

- ST - heat stable

24
Q

What are characteristics of EPEC?

A
  • Most prevalent in the developing world
  • Attacks small bowel
  • Causes severe watery diarrhea, nausea and vomiting, dehydration
  • Treatment: hydration
  • EPEC has been used to study the interaction of a bacterial pathogen with the host target cell
25
Q

How does EPEC form a intimate attachment?

A
  1. adheres and injects EspA-needle complex
  2. Tir translocated to cytoplasm
  3. Tir appears on surface of cell
  4. intamin can bind to TIR
26
Q

What are the characteristics of EHEC?

A
  • possible deaths
  • bloody diarrhea
  • HUS Hemolytic Uremic Syndrome
  • small number
  • small number can cause infection
  • can survive acidity in the stomach.
27
Q

What are the two virulence factors of EHEC?

A
  1. adhesins to epithelial cells

2. Shiga like toxins

28
Q

What is EHEC’s Shiga like toxins?

A
  • encoded by bacteriophage
  • blocks protein synthesis and lead to cell death in kidneys
  • some brain damage
  • Stx-1, stx-2
29
Q

What is a common source of EHEC?

A
  • in cattle, they are not affected by the toxin
30
Q

Why don’t you use abx on EHEC?

A

-can become toxin bombs

31
Q

What are the characteristics of EAEC?

A
  • cause watery diarrhea
  • attacks small bowel
  • chronic diarrhea in immunocompromised
32
Q

What is the pathogenic mech of EAEC?

A
  • induction of mucus secretion which traps bacteria
  • Bundle forming pili
  • Presence of cytotoxin not proven
33
Q

What are the characteristics of EIEC?

A
  • most common in developing world
  • attacks large bowel
  • causes watery diarrhea that progresses to bloody diarrhea
  • invades intestinal cell, multiplies within the cell, spreads to adjacent cells
  • cause disease similar to shigella
  • some suggest that shigella and EIEC are the same organism, just different LPS
  • EIEC use same invasion genes as shigella
34
Q

What are the characteristics of shigella?

A
  • reservoir is human GI
  • causes >200 million cases/year in diarrhea worldwide
  • highly contagious
  • serogroup based on O-antigen
  • low inoculum causes disease
  • person to person or through food
  • HUS is a complication
  • occurs in children more
35
Q

What are the four serogroups of shigella ?

A

GroupA Shigella dysenteriae

GroupB Shigella flexneri GroupC Shigella boydii GroupD Shigella sonnei

36
Q

Which strains of Shigella causes the more severe diseases?

A

S. dysenteriae and S. Flexneri

37
Q

What is the pathogenesis of Shigella?

A
  • acid tolerant
  • invades cell of the large bowel leading to ulceration and abscesses
  • type III secretion
  • progresses in cells, spreads cell to cell
  • all strains produce toxins
38
Q

what is the mech of shiga toxin?

A
  • A-B toxin
  • binds Gb3 glycolipid
  • internalized and stransported to the golgi
  • A subunit is released to the cytoplasm
  • A blocks tRNA binding
  • blocks protein synthesis
39
Q

Are there any effective vaccines for shigella and E. Coli?

A

no

Microm 442 (16 decks)

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