Infectious Causes of Gastroenteritis 2

Question 1

What are the two ways which bacteria can adhere to the cell?

Answer 1

Fimbriae (CFA or bundle forming pili) or non fimbriate (e.g. intimin)

Question 2

How does rotavirus effect intestinal architecture?

Answer 2

By growing inside enterocytes and causing them to die prematurely there is a loss of microvilli

Question 3

What is done in a laboratory diagnosis of diarrhoea?

Answer 3

macroscopic appearance, microscopy, culture, antigen detection, detection of nucleic acids

Question 4

What is light microscopy used to diagnose?

Answer 4

Parasites

Question 5

What is electron microscopy used to diagnose?

Answer 5

Viruses - if can’t be diagnosed otherwise

Question 6

What is antigen detection used to diagnose?

Answer 6

Viruses mainly - also parasites and toxins

Question 7

Why won’t you see bacteria in a stool sample microscopy of amoebic dysentry?

Answer 7

Because amoeba eat bacteria

Question 8

What does it mean if you see trophozoites of giardia lamblia in the faeces?

Answer 8

That the patient has diarrhoea - not that the giardia lamblia caused the diarrhoea

Question 9

What does it mean if you see trophozoites of entamoeba histolytica with red blood cells inside it?

Answer 9

That the entamoeba histolytica is acting as a pathogen not a commensal

Question 10

What type of stain would you use for cryptosporidium?

Answer 10

ZN stain

Question 11

Which bacteria would you need enrichment to culture?

Answer 11

salmonella

Question 12

Why do you need to tell the lab which pathogen you are looking for in the sample?

Answer 12

Because each pathogen requires specific media for culture

Question 13

Which pathogen would you use serotyping for?

Answer 13

salmonella typhee

Question 14

Which pathogen would you use pathotyping for?

Answer 14

organisms which are pathogenic and non pathogenic - such as E. coli

Question 15

How do you diagnose a viral infection?

Answer 15

Mainly by antigenic detection, sometimes by PCR and as a last resort by electron microscopy

Question 16

What is most important in the treatment of diarrhoea?

Answer 16

Replacing lost fluid and electrolytes - either oral or intravenous

Question 17

What is in oral rehydration salts?

Answer 17

sodium chloride, potassium chloride, sodium bicarbonate, glucose

Question 18

How is water taken up by villus cells?

Answer 18

By following sodium and chloride ions and solutes to maintain the osmotic gradient

Question 19

Why is water absorption insufficient in diarrhoea?

Answer 19

Because the sodium/chloride pump is inactive during diarrhoea

Question 20

Why does oral rehydration work?

Answer 20

Because the pump which takes up solutes (glucose) and sodium is active during diarrhoea - so if glucose can be taken up then water will follow

Question 21

What are the 3 types of anti-diarrhoeals?

Answer 21

anti-motility agents, anti-secretory agents, binding agents

Question 22

How do anti-motility agents work?

Answer 22

By stopping peristalsis

Question 23

Do anti-motility agents stop dehydration?

Answer 23

No

Question 24

What is synsorb-Pk?

Answer 24

A shiga toxin receptor attached to sand - to absorb shiga toxin from the gut

Question 25

Why doesn’t synsorb-Pk work?

Answer 25

Because by the time you diagnose enough toxin has already been absorbed

Question 26

Which types of diarrhoea would you use antibiotics for?

Answer 26

cholera, typhoid fever, shigella, protozoal infections, pseudomembranous colitis

Question 27

For which type of diarrhoea is there an immunisation against?

Answer 27

rotavirus