L7 GIT Infections

Question 1

What is the normal human flora?

Answer 1

Microbiome on the human body where organisms naturally exist

Question 2

Where is there an increased human microbiome?

Answer 2

Moist, protected areas of skin e.g. armpits, groin and between toes

Question 3

Microbial cells: human cells

Answer 3

10:1

Question 4

Commensal flora of gut (bacteria type)

Answer 4

More obligate anaerobic bacteria (e.g. bacteroides) than facultative anaerobic bacteria (e.g. E. coli) by 100:1

Question 5

What are the beneficial effects of gut commensal flora?

Answer 5

Metabolism
Colonisation resistance
Antibody induction

Question 6

Why does diet effect the composition of gut flora?

Answer 6

Bottle-fed babies develop adult microflora

Breast-fed babies develop ‘Bifidobacteria’ = probiotics that help to perform essential functions such as digestion

Question 7

Most common gut commensal flora

Answer 7

Bacteroides

Prevotella

Question 8

Obligate anaerobes

Answer 8

Clostrodia

Bifidobacteria

Question 9

Facultative anaerobes

Answer 9

Enterobacteriacea

Enterococci

Question 10

Bacterial gastroenteritis (enterotoxin production)

Answer 10

Vibrio cholerae
E. Coli
Shigella dysenteriae
C. perfingens
S. aureus
B. cereus
C. difficile

Question 11

Bacterial gastroenteritis (adherence)

Answer 11

Shigella sonnei
E. coli
Campylobacter jejuni
Salmonella

Question 12

Cholera cause

Answer 12

Vibrio Cholerae

Question 13

Symptoms of cholera

Answer 13

Diarrhoea and vomiting

Question 14

Transmission of cholera

Answer 14

Faecal-oral route (toxin mediated)

Question 15

Management of cholera

Answer 15

Oral vaccine

Oral rehydration solution

Question 16

What does salmonella enterica cause?

Answer 16

Food poisoning
Typhoid
Paratyphoid

Question 17

Serovars of salmonella enterica

Answer 17

2500 serovars

Salmonella Newport is most common

Question 18

Salmonella enterica cause

Answer 18

Contaminated foodstuff e.g. poultry

Question 19

Mechanism of salmonella enterica

Answer 19

Type three secretion systems

Question 20

Gastroentiritis treatment

Answer 20

Supportive management
Avoid antibiotics
May worsen E.coli HUS

Question 21

Pathotypes of E.coli

Answer 21

8 pathotypes

Question 22

E. coli O157

Answer 22

Cattle was a major source

Toxin causes premature destruction of RBC (clog kidneys) causing haemolytic-uremic syndrome (HUS)

Question 23

E.coli mechanism

Answer 23

Toxin activates G protein
Increase cAMP
Activates ion channels (increase chloride excretion)
Water follows out of cell

Different toxins have different mechanisms

Question 24

Common cause of C. difficile

Answer 24

From nosocomial infections

Question 25

Symptoms of C. difficile

Answer 25

Diarrhoea
Toxic megacolon
Pseudomembranous colitis (inflammation of large intestine)

Question 26

C. difficile mechanism

Answer 26

Toxin A: active component with toxic effects (increasing production of cAMP)
Toxin B: facilitate binding to certain receptor

Binary toxin

Question 27

C. difficile: Overview of intracellular modification by TcdA and TcdB

Answer 27

Both act intracellularly as glycosyltransferases
Each toxin modifies small GTPases
Effects of modification = actin condensation/ transcriptional activation/ apoptosis

Exposure of TcdA = neutrophil infiltration, substance P production, chemokine production, reactive oxygen intermediate production, disruption of tight junctions and apoptosis
Exposure of TcdB leads to disruption of tight junctions and apoptosis

Combination of one or more of these activities leads to fluid accumulation in the host and inflammatory responses

Question 28

Campylobacter complications

Answer 28

Reactive arthritis, Guillian-Barre syndrome, and BS

Question 29

Campylobacter causes

Answer 29

Raw or undercooked meat
Unpasteurised milk
Untreated water

Question 30

Outbreak of campylobacter

Answer 30

Clustering of cases due to common source e.g. recreational water/ food and water sources