98 - Gastrointestinal Infections II Flashcards
When is a specific diagnosis of diarrhoea made?
When it has persisted for a while
Appearance of a microscope slide of amoebic dysentery
Few bacteria, as amoebae eat them
What does presence of Giardia trophozoites in diarrhoea mean?
Giardia hasn’t had time to encyst before being passed out of the body. Doesn’t necessarily mean that Giardia is causing disease.
What do Entamoeba histolytica eat?
RBCs
How are Cryptosporidia visualised?
Modified Ziehl-Neelsen stain
Most common form of identified bacterial diarrhoea in Australia
Salmonella
How are Salmonella found in faeces culture?
Enrichment broth (selenite)
Difficulty in identification of viral gastro
Very hard to grow in cell culture
How are viral causes of gastro often identified?
Electron microscopy, nucleic acid detection (PCR), antigen detection
Example of a viral cause of gastro that can’t be grown
Enteric adenovirus
Priority in diarrhoea treatment
Replacing fluid and electrolytes (NOT stopping diarrhoea).
Maybe reduce fluid loss.
How is water transported from gut lumen into the blood?
Passively.
Through diffusion of ions (Na+, Cl-), osmotic movement of water.
Water transport mechanism still active in diarrhoea
Na+/solute (often glucose) cotransport is still active
How can fluid loss be reduced in diarrhoea?
1
2
3
1) Anti-motility agents
2) Anti-secretory agents
3) Binding agents
Example of an anti-motility agent
Codeine (reduces peristalsis)
Conditions for which antimicrobials can be useful 1 2 3 4 5 6
1) Cholera (reduces amount of time which cholera is excreted)
2) Systemic infections (EG: typhoid fever)
3) Immunocompromised patients
4) Serious Shigella infections
5) Protozoal infections (always treated, even when asymptomatic)
6) Pseudomembranous colitis
Problem with treatment for cholera
Resistant to many antibiotics. Need to test resistances.
Where does diarrhoea rank as worldwide cause of death under five years?
Third
Most important treatment for diarrhoea
Oral rehydration salts
Enteric pathogen that can be made worse with antimicrobial treatment
EHEC.
When bacterium is stressed by antimicrobial, phages in bacteria are activated (prophage form -> phage form), begin replicating.
As shigatoxin is phage-encoded, this results in more shigatoxin formation.
When bacterium is lysed, lots of shigatoxin is released.
Enteric pathogen that can be made worse with antimicrobial treatment, mechanism of action
EHEC.
When bacterium is stressed by antimicrobial, phages in bacteria are activated (prophage form -> phage form), begin replicating.
As shigatoxin is phage-encoded, this results in more shigatoxin formation.
When bacterium is lysed, lots of shigatoxin is released.
Enteric pathogen that can be made worse with antimicrobial treatment, mechanism of action
EHEC.
When bacterium is stressed by antimicrobial, phages in bacteria are activated (prophage form -> phage form), begin replicating.
As shigatoxin is phage-encoded, this results in more shigatoxin formation.
When bacterium is lysed, lots of shigatoxin is released.
