Infectious Causes of Gastroenteritis 2 Flashcards
What are the two ways which bacteria can adhere to the cell?
Fimbriae (CFA or bundle forming pili) or non fimbriate (e.g. intimin)
How does rotavirus effect intestinal architecture?
By growing inside enterocytes and causing them to die prematurely there is a loss of microvilli
What is done in a laboratory diagnosis of diarrhoea?
macroscopic appearance, microscopy, culture, antigen detection, detection of nucleic acids
What is light microscopy used to diagnose?
Parasites
What is electron microscopy used to diagnose?
Viruses - if can’t be diagnosed otherwise
What is antigen detection used to diagnose?
Viruses mainly - also parasites and toxins
Why won’t you see bacteria in a stool sample microscopy of amoebic dysentry?
Because amoeba eat bacteria
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
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
What type of stain would you use for cryptosporidium?
ZN stain
Which bacteria would you need enrichment to culture?
salmonella
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
Which pathogen would you use serotyping for?
salmonella typhee
Which pathogen would you use pathotyping for?
organisms which are pathogenic and non pathogenic - such as E. coli
How do you diagnose a viral infection?
Mainly by antigenic detection, sometimes by PCR and as a last resort by electron microscopy
What is most important in the treatment of diarrhoea?
Replacing lost fluid and electrolytes - either oral or intravenous
What is in oral rehydration salts?
sodium chloride, potassium chloride, sodium bicarbonate, glucose
How is water taken up by villus cells?
By following sodium and chloride ions and solutes to maintain the osmotic gradient
Why is water absorption insufficient in diarrhoea?
Because the sodium/chloride pump is inactive during diarrhoea
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
What are the 3 types of anti-diarrhoeals?
anti-motility agents, anti-secretory agents, binding agents
How do anti-motility agents work?
By stopping peristalsis
Do anti-motility agents stop dehydration?
No
What is synsorb-Pk?
A shiga toxin receptor attached to sand - to absorb shiga toxin from the gut
Why doesn’t synsorb-Pk work?
Because by the time you diagnose enough toxin has already been absorbed
Which types of diarrhoea would you use antibiotics for?
cholera, typhoid fever, shigella, protozoal infections, pseudomembranous colitis
For which type of diarrhoea is there an immunisation against?
rotavirus
