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Food Borne Pathogens > Lecture 10- Escherchia coli > Flashcards

Lecture 10- Escherchia coli Flashcards

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1
Q

E.coli

A
  • gram negative, motile, nonsporulating, rod-shaped, and a facultative anaerobe
  • part of the normal microbial population of the intestine track of humans, and other warm blooded animals
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2
Q

Why can E.coli be used as an indicator for fecal contamination?

A

-E.coli is found in the large intestine in the millions of cells per gram

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3
Q

What determines the phenotype and disease caused by each phenotype of E.coli?

A

virulence factors they pick up via horizontal gene transfer determines which phenotype they get

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4
Q

Enteropathogenic E.coli (EPEC)

A
  • has the ability to form distinctive lesions on the surfaces of intestinal epithelial cells
  • Locus of enterocyte effacement (LEE) genes
  • generally does not have enterotoxins
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5
Q

Which group does EPEC effect the most?

A

-children in developing countries

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6
Q

How is EPEC transmitted?

A

Fecal-oral route, humans are the only identified carrier

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7
Q

How do you prevent transmission of EPEC?

A

-follow proper hygiene methods, have clean fresh water supplies

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8
Q

How does EPEC cause diarrhea?

A
  • effacement of microvilli may lead to a decrease in absorptive surfaces thereby contributing to diarrhea by increasing water in the small intestine
  • tight junction may be disrupted leading to increased intestinal permeability
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9
Q

Shiga toxin producing E.coli (STEC)

A
  • presence of Shiga toxin 1 or 2 which is acquired by bacteriophage infection
  • has LEE genes and forms lesions on the microvili
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10
Q

What is the most common serotype of STEC?

A

O157:H7

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11
Q

How is STEC transmitted?

A

Via fecal oral rout
Cattle are major reservoir for STEC
Infectious dose is very low

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12
Q

What symptoms can STEC cause?

A
  • mild to bloody diarrhea

- Haemolytic uremic syndrome (HUS)

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13
Q

What is Haemolytic uremic syndrome (HUS)?

A

-caused by the destruction of RBC. The damaged RBC clog the filtering system in the kidneys which can lead to life-threatening kidney failure.

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14
Q

Are antibiotics recommended for STEC?

A

-No, because antibiotics cause stress and therefore forces the strain to leave the E.coli and invade another E.coli

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15
Q

Enteroinvasice E.coli/ Shigella (EIEC)

A
  • facultative intracellular pathogens

- invasive and divide in the intracellular milieu of intestinal cells

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16
Q

How does the infection process work for EIEC?

A
  • cells penetrate the epithelial barrier, induce macrophage cell death, invade intestinal epithelial cells, engagement in intra- and intercellular movement, and degrade epithelial integrity
  • destabilize the epithelial tight junctions and induce epithelial cell death
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17
Q

What is the inflammatory response to the infection caused by EIEC?

A

-apoptotic macrophage and IEC invasion perforates the epithelial barrie and leads to tissue lesions

18
Q

Do EIEC and Shigella have the same virulence strategies?

A

-yes but Shigella has increased virulence

19
Q

What are the symptoms of EIEC/Shigella?

A
  • mild watery diarrhea, fatigue, malaise, fever, anorexia
  • later in the disease there may be abdominal cramps, blood, mucus in diarrhea and dehydration
  • usually self-limiting
  • HUS may happen from Stx toxin
20
Q

What are the treatments for EIEC/ Shigella

A
  • oral rehydration
  • antibiotics shorten the duration of illness, unlike STEC, antibiotics seem to protect against HUS
  • Antibiotic resistance is high
21
Q

What is Enteroaggregative E.coli (EAEC) known for?

A
  • most common bacterial pathogen identified in patients with diarrhea
  • causes persistent diarrhea in children, immunocompromised patients
22
Q

How is EAEC transmitted?

A

food and water contaminated with fecal material

-found in calves, piglets, horses

23
Q

What is the three part infection model of EAEC?

A
  1. cells adhere to intestinal mucosa
  2. cells produce enterotoxins and cytotoxins
  3. the mucosa becomes inflamed due to toxins and the immune system (diarrhea)
24
Q

Which E.coli is the only one to have a heat-stable toxin?

A

Enterotoxigenic E.coli (ETEC)

-heat-stable toxin acts by inducing chloride and fluid secretion into the lumen

25
Q

Which E.coli is the major cause of traveler’s diarrhea?

A

Enterotoxigenic E.coli (ETEC)

26
Q

ETEC toxin

A

-enterotoxin can be heat liable or heat stable and produces several colonization factors for adherence to the intestinal epithelium

27
Q

ETEC virulence factors?

A
  • No virulence factors are in the core-genome of ETEC

- acquisition of plasmid borne toxins and virulence factors may be the driving force behind ETEC pathogenesis

28
Q

What is the recovery period of ETEC?

A

-illness has a rapid onset, symptoms appear quickly in 5 hours, but generally take 1-2 days, duration of the illness is 3-5 days

29
Q

Are antibiotic treatment recommended for ETEC?

A
  • no, since it will clear up on its own

- Antimicrobial resistance?

30
Q

Diffusely Adherent E.coli (DAEC)

A
  • diffuse pattern of adherence to epithelial cells, adherence occurs over the entire surface of the epithelial cell
  • DAEC binds to the epithelial cell, induces actin rearrangement and destroys the microvilli, tight junctions become leaky
31
Q

How is DAEC transmitted?

A

Transmission/Reservoir is unknown

32
Q

What is the defining virulence factor of DAEC?

A

Afa/Dr family of adhesins which allow for the diffuse binding to epithelial cells (fimbriae)

33
Q

What is the treatment for DAEC?

A

Oral rehydration

most are already resistant to most antibiotics

34
Q

Adherent Invasive E.coli (AIEC)

A

-most related to UPEC

but UPEC strains don’t have the adhesion invasion, and intracellular replication traits that identify the AIEC pathotype

35
Q

Which E.coli is most associated to be a causation agent of Crohn’s disease?

A

Adherent Invasive E.coli (AIEC)

-capable of invading epithelial cells as well as replicating within macrophages

36
Q

Do AIEC express virulence factors?

A

No, mechanism of its proinflammatory and invasive phenotype is not fully understood

37
Q

What do ETEC use for attachment to host intestinal cells?

A

Colonization factors (CFs)

38
Q

Which E.coli forms biofilms on the intestinal mucosa, and bacteria adhere to each other as well as to the cell surface to form an aggregative adherence pattern known as stacked brick

A

EAEC

39
Q

What is the difference between the LEE for EPEC and STEC?

A

EPEC: LEE and bundle forming pilus gene (bfp)
STEC: LEE as well as Shiga toxin genes (stx1, stx2, or a combination)

40
Q

Where are the EAEC virulence factors found?

A

pAA plasmid

41
Q

Which Ecoli are most common in E.coli (4)

A

STEC, ETEC, EAEC, EIEC

Food Borne Pathogens (14 decks)

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