Lecture 10-E coli

Question 1

What are the characteristics of E coli?

Answer 1

1. gram neg
2. motile
3. non sporulating
4. rod shaped
5. facultative anaerobe
6. part of normal microbial population of intestinal track of humans and other warm blooded animals

Question 2

How may E coli be categorized?

Answer 2

into diff types of pathotypes base on their ability to produce toxins, adhere to epithelial cells and ability to invade epithelial cells

Question 3

the pathogenic traits of E coli have mostly been acquired through?

Answer 3

horizontal gene transfer

Question 4

E coli is differentiated into serotypes based on what 3 major surface antigens?

Answer 4

O (LPS), H(flagella) and K (capsule)

Question 5

The ___ antigen defines the serogroup of a strain and the ___antigen identifies the serotype

Answer 5

O and H

Question 6

___ has the ability to form distinctive lesions on the surface of intestinal epithelial cells

Answer 6

Enteropathogenic E coli (EPEC)

Question 7

EPEC is only transmitted via ___

Answer 7

fecal oral route, humans the only carrier, environmental reservoirs have not been identified.

Question 8

T or F: EPEC generally has enterotoxins

Answer 8

F

Question 9

What is the mechanism of diarrhea production by EPEC?

Answer 9

so there is obvious deformation of the enterocyte cells (effacement of microvilli) but the exact production of diarrhea production is not understood for EPEC. the effacement of microvilli may lead to a decrease in absorptive surfaces thereby contributing to diarrhea by increasing water in the small intestine. Tight junctions also disrupted = increased intestinal permeability.

Question 10

__ can cause mild to bloody diarrhea and haemolytic uremic syndrome

Answer 10

STEC

Question 11

what is HUS? how is it caused

Answer 11

haemolytic uremic syndrome. It is caused by the destruction of red blood cells. The damaged red blood cells clog the filtering system in the kidneys which can lead to life threatening kidney failure.

Question 12

most common serovar for STEC is

Answer 12

O157:H7

Question 13

transmission for shiga toxin producing E coli occurs via the

Answer 13

fecal oral route (cattle); lysogenic phage thereafter

Question 14

Why are antibiotics not recommended to treat STEC?

Answer 14

Stx toxin are carried on lysogenic phage which may become lytic during bacterial stress, antibiotics cause stress and therefore are not recommended; under stress it can affect other strains of E coli that dont naturally have the shiga toxin so you would be spreading it even more.

Question 15

EIEC and ___ are facultative intracellular pathogens

Answer 15

Shigella

Question 16

explain how infection may occur for by EIEC -shigella.

Answer 16

1. they are invasive and divide in the intracellular milieu of intestinal cells
2. infection is a multistep process, cells penetrate the epithelial barrier, induce macrophage cell death, invade intestinal epithelial cells, engagement of intra and intercellular movement and degrade epithelial integrity.
3. destabilize the tight junctions and induce epithelial cell death.

Question 17

The massive inflammatory response is associated with ____ and ____ and leads to ____ (characteristic of EIEC/shigella)

Answer 17

1. apoptotic macrophages and EIEC invasion perforates the epithelial barrier and leads to tissue lesions.

Question 18

what are some symptoms of EIEC shigella

Answer 18

• mild watery diarrheal, fatigue, malaise, fever and anorexia.
• later in the disease there may be abdominal cramps, blood and mucus in the diarrheal and dehydration
• HUS can also occur

Question 19

what are some effective treatments for EIEC/shigella ?

Answer 19

oral rehydration (think diarrhea, antibiotics to shorten duration of illness)

Question 20

T or F: unlike STEC, antibiotics seem to protect against HUS with EIEC/shigella

Answer 20

True

Question 21

1. Common in North America
2. May be the most common bacterial pathogen identified in patients with diarrheal
3. found in calves, piglets and horses
4. transmitted through food and water contaminated with fecal matter

Answer 21

Enteroaggregative E coli (EAEC)

Question 22

There exists great variability in virulence factors and toxins between EAEC strains, but a three part infection model is characteristic of EAEC infection. What are they?

Answer 22

1. cells adhere to intestinal mucosa
2. cells produce enterotoxins and cytotoxins
3. mucosa becomes inflamed due to toxins and the immune system

Question 23

The identifying factor of EAEC strains is….

Answer 23

pAA virulence plasmid.

Question 24

a very diverse pathotype and major cause of travelers diarrhea and endemic in most underdeveloped countries

Answer 24

ETEC- enterotoxinogenic E coli

Question 25

can produce either or both heat labile or heat stable enterotoxins and produce several colonization factors for adherence to intestinal epithelium

Answer 25

ETEC

Question 26

what is the MOST defining characteristic of ETEC

Answer 26

it is the only Ecoli to have a heat stable toxin

Question 27

The heat stable toxin in ETEC works by ___

Answer 27

inducing chloride and fluid secretion into the lumen thus diarrhea

Question 28

ETEC exposure occurs via___

Answer 28

the fecal oral route, exposure from contaminated food and drinking water.

Question 29

Symptoms of ETEC and potential treatments include

Answer 29

symptoms: mild-severe (non bloody) diarrhea --> dehydration, headaches, fever, abdominal cramping, nausea and vomiting. very rapid onset, duration illness 3-5 days treatment: hydration, electrolyte

Question 30

DAEC stands for

Answer 30

Diffusely adherent E coli

Question 31

What is special about the way DAEC cause infection?

Answer 31

1. They attach to epithelial cells but don't follow the classical pattern of adherence such as attachment and effacement of microvilli. Adherence of DAEC occurs over the entire surface for the epithelial cells.

Question 32

what happens when DAEC bind to epithelial cells?

Answer 32

1. induce actin rearrangement and destroy the microvilli, tight junctions become leaky

Question 33

what is the recommended treatment for DAEC

Answer 33

oral rehydration because several strains are already resistant to most antibiotics

Question 34

causative agent of crohns disease

Answer 34

adherent invasive Ecoli

Question 35

___ and ___ are extracellular pathogens that attach to intestinal epithelium and efface microvilli forming characteristic A/E lesions

Answer 35

EPEC and Lee positive STEC

Question 36

___ uses colonization factors for attachment to host intestinal cells

Answer 36

ETEC

Question 37

___ forms biofilms on the intestinal mucose and bacteria adhere to eachother as well as to the cell surface to form an aggregative adherence pattern (AA) known as stacked brick

Answer 37

EAEC

Question 38

___ is dispersed over the surfaces of intestinal cells, resulting in diffuse adherence (DA) pattern

Answer 38

DAEC

Question 39

___ colonizes the intestinal mucosa of patients with Crohns disease and is capable of invading epithelial cells as well as replicating within macrophages

Answer 39

AIEC (adherent invasive)

Question 40

_____ are intracellular pathogens that penetrate the intestinal epithelium through __ cells to gain acess to the ___.

Answer 40

EIEC/shigella, M cells, submucosa

Question 41

EIEC - Shigella escape submucosal macrophages by ___ followed by ____

Answer 41

induction of macrophage cell death, followed by basolateral invasion of colonocytes and lateral spread.

Question 42

Lee genes lead to what? these are found in?

Answer 42

effacement of microvilli and EPEC + STEC

Question 43

ETEC isolates carry what enterotoxins

Answer 43

LT and ST solely together on plasmids.

Question 44

DAEC isolates have ____ that enhance adherence called the Afa/Dr

Answer 44

fimbrae

Question 45

EAEC virulence factors are foiund on the ____

Answer 45

pAA plasmid

Question 46

T or F: genes involved in the pathogenesis of AIEC strains are unclear

Answer 46

T

Question 47

__ gained the ability to invade cells mainly through the pINV plasmid and acquired additional virulence traits in the form of PAIs

Answer 47

EIEC/shigella

Question 48

important virulence factors include genes that encode the ability to

Answer 48

1. adhere to epithelial cells 2. produce toxins 3. invade epithelial cells

Question 49

In food, the common E coli pathotypes are ___, ___, ___ and ___

Answer 49

STEC, ETEC, EAEC and EIEC