Infectious Causes of Gastroenteritis 2 Flashcards Preview

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Flashcards in Infectious Causes of Gastroenteritis 2 Deck (27):
1

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

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

2

How does rotavirus effect intestinal architecture?

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

3

What is done in a laboratory diagnosis of diarrhoea?

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

4

What is light microscopy used to diagnose?

Parasites

5

What is electron microscopy used to diagnose?

Viruses - if can’t be diagnosed otherwise

6

What is antigen detection used to diagnose?

Viruses mainly - also parasites and toxins

7

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

Because amoeba eat bacteria

8

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

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

9

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

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

10

What type of stain would you use for cryptosporidium?

ZN stain

11

Which bacteria would you need enrichment to culture?

salmonella

12

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

Because each pathogen requires specific media for culture

13

Which pathogen would you use serotyping for?

salmonella typhee

14

Which pathogen would you use pathotyping for?

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

15

How do you diagnose a viral infection?

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

16

What is most important in the treatment of diarrhoea?

Replacing lost fluid and electrolytes - either oral or intravenous

17

What is in oral rehydration salts?

sodium chloride, potassium chloride, sodium bicarbonate, glucose

18

How is water taken up by villus cells?

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

19

Why is water absorption insufficient in diarrhoea?

Because the sodium/chloride pump is inactive during diarrhoea

20

Why does oral rehydration work?

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

21

What are the 3 types of anti-diarrhoeals?

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

22

How do anti-motility agents work?

By stopping peristalsis

23

Do anti-motility agents stop dehydration?

No

24

What is synsorb-Pk?

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

25

Why doesn’t synsorb-Pk work?

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

26

Which types of diarrhoea would you use antibiotics for?

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

27

For which type of diarrhoea is there an immunisation against?

rotavirus