GI Infections

Question 1

What is the Bristol stool chart?

Answer 1

Diagnostic medical tool designed to classify the form of human faeces into seven categories

1+2 = constipation

3+4 = normal

5-7 = diarrhoea

Question 2

What questions needs to be asked when managing diarrhoea?

Answer 2

Duration

Frequency

Travel

Exposure/contact history – farm animal, sewage

Co-morbidities

Chemo, transplant, immunedef

Occupation = health worker, work with young children, care-worker

Question 3

In general how are GI infections managed?

Answer 3

History = particularly travel and exposure history

Physical exam = include hydration status

Samples = request the right test

Treat = fluids, +/- Abx

Infection prevention

Question 4

What are the major bacterial causes of infective diarrhoea?

Answer 4

Salmonella

Campylobacter jejuni

Shigella

Enterotoxigenic E. coli

Clostridium difficile

Question 5

What are the major viral causes of infective diarrhoea?

Answer 5

Norovirus

Rotavirus

Adenovirus

Question 6

What are the major causes of parasitic infective diarrhoea?

Answer 6

Cryptosporidium

Giardia

Entamoeba

Cyclospora cayetanensis

Question 7

How is a stool sample cultured?

Answer 7

On selective agar = enables particular MO to grow

Stool contain huge number of natural flora

Question 8

How does camplylobacter appear on gram stain?

Answer 8

Gram -ve

‘Seagull appearance’ = spirochete

Question 9

How is campylobacter transmitted?

Answer 9

Food

Water

Direct contact with animals/animal products

Question 10

Describe the symptoms seen in a campylobacter infection

Answer 10

Abdominal pain, cramps

Diarrhoea (may be absent or bloody)

Nausea

Prodromal symptoms (fever, rigors, aches, dizziness)

Colitis

May mimic appendicitis

Question 11

Outline the acute complications of campylobacter

Answer 11

Cholecystitis

Peritonitis

Rash

Septic pseudoaneuysm

Pericarditis and myocarditis

Focal extraintestinal infections.

Question 12

Outline the late complications of campylobacter

Answer 12

Reactive arthritis

Guillain—barre syndrome – muscle paralysis may be to the extent where they need ventilation

Question 13

What special stain is used when there is a travel history accompanying diarrhoea?

Answer 13

Modified acid-fast stain

Question 14

How is a camplyobacter infection treated?

Answer 14

Self limiting

Abx only when severe = fluoroquinolone or macrolide (only reduced symptom length by a day = limited purpose)

Question 15

What is cyclospora cayetanensis and what does it cause?

Answer 15

Coccidian parasite

Travellers diarrhoea

Question 16

How is cyclospora cayetanensis transmitted?

Answer 16

Faeco-oral transmission via contaminated food/water

Question 17

Describe the symptoms seen in cyclospora cayetanensis infection

Answer 17

Average length of illness = ~3 weeks
Anorexia 
Nausea 
Flatulence 
Fatigue
abdominal cramping 
watery diarrhea 
low-grade fever 
weight loss

Question 18

How is cyclospora cayetanensis treated?

Answer 18

Fluid rehydration

Trimethoprim-sulphamethoxazole

Question 19

What is a lateral flow test?

Answer 19

Intended to detect presence/absence Ag/Ab

Question 20

What lab technique is used to identify the norovirus?

Answer 20

Electron microscopy

Question 21

What is the most common cause of epidemic gastroenteritis?

Answer 21

Norovirus

Question 22

How is norovirus transmitted?

Answer 22

Faeco-oral, person-to-person

<100 viral particles required

Question 23

How is a norovirus infection treated?

Answer 23

Fluid rehydration

No antiviral treatment available

Question 24

Describe the key features of the gut immune response to infection

Answer 24

Villi and underlying surface = host immune cells

Peyer patches = scattered along surface, contain T/B cells, dendritic cells (IL-6, 12), macrophage, running to mesenteric lymph node

Mucosal barrier on the ep

M cells = enables transcytosis for Ag sampling

IL-10 = anti-inflam cytokine

Question 25

Outline the function of gut-associated lymphoid tissue (GALT)

Answer 25

Largest collection of lymphoid tissues in the body

Consisting = mesenteric lymph nodes, peyers patches

Carry out immune attacks and education of the immune system = defence against pathogens

Question 26

Describe the importance of the gut microbiome and the role of commensal organisms

Answer 26

Helps control digestion

Controls immune system = communicates with immune cells controlling how they respond

Question 27

Describe an approach to a patient presenting with traveller’s diarrhoea

Answer 27

Take a history = travel

Explore symptoms = nausea, fatigue, abdo cramping, watery diarrhoea, low-grad fever

Causes = giardia, entamoeba, cyclospora cayentanensis

Question 28

Describe the key features of Cryptosporidium

Answer 28

Parasite

Symptoms = watery diarrhoea, abdo pain, nausea, vomiting

Transmission = via faeces or coughing formites

Treat = most people recover without treatment, consume fluids

Question 29

How can a parasitic infection of the GI tract be diagnosed?

Answer 29

Enzyme immunoassay (EIA)

Faecal stool exam = 3 or more samples on separate days

Cellophane tape test = looking for eggs

Endoscopy = used when stool exams do not reveal cause

Serology = Ab or parasitic Ag

Blood smear = under a microscope

Question 30

Describe the importance of infection prevention and infection control measures with regard to GI infections

Answer 30

Hand washing
Not sharing food
PPE
Isolation
Environmental cleaning 
48hr rule

Question 31

What are the causes of travelers diarrhoea?

Answer 31

giardia

entamoeba

cyclospora cayentanensis