12.1-12.2

Question 1

___ is the third leading cause of death in children

Answer 1

Diarrhoea

Question 2

Diarrhoea of small intestinal origin occurs when:

Answer 2

Amount of fluid entering LARGE intestine (from SI) exceeds capacity for absorption.

Question 3

Diarrhoea of large intestinal origin occurs when:

Answer 3

Large intestine is inflamed, and may be blood or pus in stools.

Question 4

In dysentery, there is ___, ___ and ___ is faeces.

Answer 4

Blood, pus and mucus.

May see in cancer and ulcerative colitis too.

Question 5

Non-specific gastroenteritis is a disease of the ___ ___ and/or ___ ___, and usually NOT the ___.

Answer 5

Small intestine and large intestine.
Usually not stomach!
So gastroenteritis is a misnomer.

Question 6

Dysentery is caused by ___

Answer 6

Shigella/EIEC (basically same).

Question 7

A protozoan that causes dysentery is ___ ___

Answer 7

Entamoeba histolytica (amoebic dysentery).

Question 8

Foodborne diarrhoeas are commonly caused by ___ in Australia

Answer 8

Salmonella

Question 9

Foodborne diarrhoeas are caused by ___ (many), other than Salmonella

Answer 9

Vibrio - not only cholerae.
Campylobacter esp. in birds like chickens (due to zoonosis).
EHEC - mostly in cows.
Viruses e.g. norovirus.
Staphylococcal enterotoxin is a superantigen.
Clostridium esp. perfringens (due to toxins).
Bacillus esp. cereus (produces toxin similar to cholera toxin).
Ciguatoxin (in some fish).

Question 10

The infectious dose of ___ is VERY LOW, less than 100 organisms.

Answer 10

EHEC

Question 11

The most common cause of travellers’ diarrhoea is ___

Answer 11

ETEC (approx. 50% of cases).

Question 12

Other bacteria that cause travellers’ diarrhoea apart from ETEC include ___ and ___.

Answer 12

Salmonella and Campylobacter

Question 13

When people take ___, sometimes develop diarrhoea.

Answer 13

Antibiotics (approx. 20-30% of people)!

Question 14

The most severe form of antibiotic associated diarrhoea is called ___ ___

Answer 14

Pseudomembranous colitis

Question 15

Pseudomembranous colitis is due to ___ ___

Answer 15

Clostridium difficile

Question 16

C. difficile normally lives in ___ of many healthy people, but can flare up when taking some antibiotics.

Answer 16

Gut

Question 17

Haemorrhagic colitis is almost always caused by ___ in Australia

Answer 17

EHEC

Question 18

In other countries (not Australia), haemorrhagic colitis is often caused by ___ ___

Answer 18

Shigella dysenteriae

Question 19

EHEC is a strain of ___ ___ that produces ___ toxin.

Answer 19

E. coli, produces Shiga toxin.

Question 20

The toxin encoded by EHEC is ___-encoded.

Answer 20

Phage

Question 21

Shiga toxin is originally from Shigella dysenteriae type ___

Answer 21

1 (and ONLY type 1!)

Note - in S. dysenteriae, the Shiga toxin is CHROMOSOMALLY encoded.

Question 22

4 species of Shigella infect humans but the most severe form is ___ ___

Answer 22

Shigella dysenteriae

Question 23

___ toxin causes haemorrhagic colitis.

Answer 23

Shiga

Question 24

How to differentiate between dysentery and haemorrhagic colitis from stool?

Answer 24

In dysentery - blood, pus and mucus.

In haemorrhagic colitis - lots of blood, not always with pus or mucus.

Question 25

Other species of Shigella (i.e. not dysenteriae), ONLY cause ___ and NOT ___ ___

Answer 25

E.g. Shigella flexneri.

ONLY dysentery and NOT haemorrhagic colitis (or haemolytic uremic syndrome).

Question 26

The cause of cholera-like diarrhoea is ___ ___, but there is another type called non-___ ___ that is due to ___

Answer 26

Vibrio cholerae

Non-cholera diarrhoea that is due to ETEC!

Question 27

Only two serotypes of Vibrio cholerae cause epidemic cholera: O___ and O___

Answer 27

1 and 139

Question 28

Enteric fever includes ___ and ___-like (same words) illnesses

Answer 28

Typhoid

Question 29

Causes of enteric fevers include ___ ___ and ___ ___

Answer 29

Salmonella Typhi and Salmonella Paratyphi

Question 30

IpaC is an ___ ___ ___.

Answer 30

Invasion plasmid antigen.

The plasmid encodes for virulence factors that allow invasion of tissues.

Question 31

Cholera AND ETEC cause disease by ___ to small intestine surface by ___ and secreting toxins to cause disease

Answer 31

Adhesion, by fimbriae

Question 32

___ adheres to intestinal surface and causes brush border damage, causing ___-___ lesions.

Answer 32

EPEC!

Attaching-effacing lesions by disruption of cytoskeleton due to tight binding.

Question 33

___ invades through epithelium and re-invades through basal layer of epithelium before moving fro cell to cell causing cell death and release of bacteria.

Answer 33

Shigella.
(Invasion restricted to mucosa.)
Thereby causing dysentery!

Question 34

___ and ___ invade submucosa.

Answer 34

Salmonella and Campylobacter

Question 35

___ causes systemic invasion.

Answer 35

Salmonella
Classically by enteric fever Salmonella e.g. Typhi and Paratyphi.
Often cause pulmonar symptoms before diarrhoea!

Question 36

What are the 2 stages of EPEC adherence?

Answer 36

1 - plasmid mediated pili called bundle forming pili (Bfp) for initial adherence to intestine.

2 - once close, secrete chromosomally encoded toxins and express genes for proteins that allow late and STRONG adherence -> cause attaching-effacing lesions.

Question 37

The ___ ___ ___ ___ is used by many pathogens to transport toxins directly into eukaryotic cells.

Answer 37

Type 3 secretion system

T3SS is ALWAYS associated with virulence!

Question 38

An adhesin called ___ is found on outer membrane of ___

Answer 38

Intimin on EPEC

Question 39

The receptor for ___ is encoded by E. coli

Answer 39

Intimin - called translocated intimin receptor (Tir)

Question 40

Intimin is secreted into eukyarotic cells by ___ (abbrev.), and back into cytoplasmic membrane of eukaryotic cells.

Answer 40

T3SS

Question 41

Tir is a receptor for intimin AND ___

Answer 41

Actin!

Binds to actin and actin come sout of solution - soluble->filamentous - one reason for attaching-effacing lesions.

Question 42

The whole system of T3SS, Tr/intimin and other effector proteins are encoded on a single length of DNA called a ___ ___

Answer 42

Pathogenicity island

Question 43

The pathogenicity island is ALWAYS on the ___, except in Yersinia where the T3SS is on the ___

Answer 43

Chromosome

Plasmid!

Question 44

Tir and intimin are unique to ___ and ___

Answer 44

EPEC and EHEC

Question 45

Salmonella is a ___ ___ pathogen

Answer 45

Facultative intracellular

Question 46

Cholera toxin is ___-encoded

Answer 46

Phage encoded

Like Shiga toxin!

Question 47

Cholera toxin, ST and LT are cyto___

Answer 47

Tonic - stimulatory and activate cells.

Question 48

Shiga toxin is cyto___

Answer 48

Toxic

Question 49

Culture of faeces for ___ is routine

Answer 49

Salmonella

Question 50

Treatment of diarrhoea is mainly ___ ___ ___

Answer 50

Oral rehydration therapy (salt AND sugar!), or may use IV fluids.

Question 51

In diarrhoea, normal uptake of electrolytes (like coupled uptake of sodium and chloride) is ___

Answer 51

Inactive - so use other mechanism, by solutes coupled to Na+ (e.g. solutes like glucose).

Question 52

There is evidence that antibiotic treatment can worsen infection with ___

Answer 52

EHEC

Question 53

The Shiga toxin of EHEC is ___-encoded, so when exposed to antibiotics, the bacteria turns on ___ response genes that trigger phages to replicate and produce more toxin!

Answer 53

Phage
Stress response genes
So antibiotics can induce toxin production and worsen outcome.
ALSO, antibiotics, if effective, can lyse bacteria leading to release of toxins!