Diarrheagenic E. Coli And Shigella D2L1W3

Front 1

What are the diarrheagenic strains of E. coli? (7)

Back 1

ETEC (enterotoxigenic E. coli)
EPEC (enteropathogenic)
EHEC (enterohemorrhagic) and STEC (Shega toxin production)
EAEC (enteroaggregative)
EIEC (enteroinvasive)
DAEC (diffuse adhering)

Front 2

What is the disease that ETEC causes called?

Back 2

Traveler's diarrhea

Front 3

How is ETEC transmitted?

Back 3

Fecal-oral

Front 4

What are the plasmid virulence factors for ETEC? (3)

Back 4

Colonization Factor Antigens (CFA)
Heat-labile enterotoxin
Heat-stabile enterotoxin

Front 5

What do colonization factor antigens do?

Back 5

They bind E. coli to the oligosaccharides of host tissues

Front 6

How does the heat-labile enterotoxin (of ETEC) work?

Back 6

It is an AB toxin that binds to a receptor on the enterocyte and endocytosed by the cell. The A component then leaves the vesicle and enters the cell to turn on the adenylate cyclase. This stops sodium and chloride absorption and causes chloride to leave the cell and enter the lumen, which causes water to follow it. Causing diarrhea

Front 7

What about the amino acid sequence for the heat-stabile enterotoxin grants it its stability?

Back 7

6 cysteines that result in 3 disulfide bonds

Front 8

What is the difference between the heat-stable toxin from ETEC and the cholera toxin?

Back 8

Heat-stable toxin causes no damage to enterocytes, unlike cholera toxin

Front 9

How does the heat-stable toxin work?

Back 9

Enters the cell and activates guanylate cyclase, which increases cellular cGMP, which inhibits sodium absorption and chloride secretion, which causes water to go follow into the lumen - diarrhea

Front 10

What kind of lesions do EPEC form on intestinal mucosa?

Back 10

Attaching and effacing - actin rearrangement results in formation of a mesa that the EPEC sit on on top of the cell

Front 11

What does the EPEC BFP do?

Back 11

BFP - bundle-forming pilus
Causes bacteria to aggregate in microcolonies
Required for virulence

Front 12

What kind of secretion system does EPEC use?

Back 12

Type III

Front 13

Describe what LEE does in EPEC.

Back 13

LEE - locus of enterocyte effacement
Necessary and sufficient for attaching and effacing
Required for virulence
Intimin/Tir adhesin/receptor pair

Front 14

What does Tir do in EPEC?

Back 14

It is a receptor that is injected into an enterocyte's membrane, which EPEC can then use to tightly bind the enterocyte

Front 15

What does Intimin do?

Back 15

It is also a part of LEE, and it binds to Tir on the enterocyte surface to make sure the EPEC is also tightly bound

Front 16

What is the reservoir for EHEC? Where is it found?

Back 16

Reservoir - cattle
Found in contaminated food (ground beef, produce, juice), water (swimming, drinking), petting zoos, and person-to-person

Front 17

What is the major serotype for EHEC?

Back 17

O157:H7

Front 18

How do you identify EHEC by culture?

Back 18

It is lactose fermenting
Sorbitol non-fermenting

Front 19

How many bacteria are needed for EHEC to cause disease state?

Back 19

Only 100s

Front 20

Is EHEC acid-resistant or acid-sensitive?

Back 20

Resistant

Front 21

What is the pathogenesis of EHEC?

Back 21

It gets into intestine and uses a BFP to bind the enterocyte in the same was as EPEC does. However, instead of just causing watery diarrhea, EHEC secretes a Shiga-like toxin (Stx), which cleaves the rRNA, halting protein synthesis. This results in cell death and hemorrhage

Front 22

What is the difference between EPEC and EHEC?

Back 22

EHEC = EPEC + phage-encoding toxin

Front 23

What can EHEC cause?

Back 23

Bloody diarrhea
Non-bloody diarrhea
Hemolytic uremic syndrom (HUS)

Front 24

What antibiotics do you use to treat EHEC? Why?

Back 24

NONE! Antibiotics actually increase toxin production by EHEC

Front 25

Who is mainly affected by EAEC?

Back 25

Children in developing countries

Front 26

What is the pathogenesis of EAEC?

Back 26

Forms biofilms on intestinal mucosa
Fimbriae mediate attachment

Front 27

EAEC triggers the inflammatory response through which receptor?

Back 27

Toll-like receptor 5

Front 28

Which diarrheagenic bugs are the most responsible for acute gastroenteritis in children and infants?

Back 28

DAEC, EAEC, and EPEC

Front 29

How does EIEC work?

Back 29

Endocytosed by enterocyte. Once inside, it lyses its vacuole and multiplies. It uses actin filaments to move around in the cell, which allows it to move to neighboring enterocytes and infect them.

Front 30

What organism is EIEC basically like?

Back 30

Shigella

Front 31

Is E. coli a lactose fermenter or non-fermenter?

Back 31

Fermenter

Front 32

Is Shigella Gram-positive or negative?

Back 32

Negative

Front 33

Is Shigella a lactose fermenter or non-fermenter?

Back 33

non-fermenter

Front 34

What are the four species of Shigella and name one fact about each?

Back 34

S. sonnei - most common in US
S. flexneri - most common worldwide
S. dysenteriae - most sever
S. boydii - least common

Front 35

Which Shigella strain is most common in the US?

Back 35

S. sonnei

Front 36

Which Shigella strain is most common worldwide?

Back 36

S. flexneri

Front 37

Which strain of shigella is most likely to cause explosive outbreaks and epidemics?

Back 37

S. dystenteriae

Front 38

What do shigella strains typically cause?

Back 38

Watery diarrhea, dysentery, protein loss, and malnutrition in infants and children

Front 39

What is the reservoir for shigella?

Back 39

Only humans

Front 40

What size infectious dose is needed for shigella?

Back 40

10-100

Front 41

How does shigella spread?

Back 41

Person-to-person

Front 42

How does shigella work?

Back 42

Enters M cells in the gut (not enterocytes) and passes through them either directly into enterocytes next to the M cell, or it exits the basilar surface of the M cell and enters through the basilar surface of the enterocytes. Once inside cells, actin filaments propel the bacteria

Front 43

What does the intestinal epithelium look like after shigella infection?

Back 43

PMN infiltration and brush border disorganization
Also loss of intestinal epithelium integrty

Front 44

What type of secretion system does shigella use to invade cells?

Back 44

Type III

Front 45

What does shigella do that causes the "cellular splash"?

Back 45

Injects proteins into cells using a type III secretion system

Front 46

What is the immune response to shigella?

Back 46

Ipaf (from shigella) activates caspase-1 protease, which causes macrophage death and the release of IL-18 and IL-1, which causes diapedesis of PMNs that try to control infection

Front 47

In what part of the intestine does shigella infection take place?

Back 47

Large intestine

Front 48

How does S. dysenteriae work?

Back 48

It secretes Shiga toxin, which cleaves the 28S ribosomal rRNA and can lead to Hemolytic Uremic Syndrome (HUS)