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RE: Thought process...

in STEMGeeks2 years ago

For the case of patient samples, I am sure mistakes in which multiple organisms end up in the same plate occur once in a while, don't they?

 2 years ago 

The short answer is yes. The test would then have to be repeated.

Each patient sample is inoculated into their own set of plates.

When we perform susceptibility testing, we make "purity plates" as proof that whatever colonies we picked were pure and the antibiotic resistance is not the result of different organisms mixing into the testing wells.

Mixing happens when a patient has multiple organisms and the microbiologist was not able to get a clean pick. Contamination can also happen when one tries to "economize" and put multiple organisms on the same purity plate (from the same or different patient).

Unless there's a supply constraint, I prefer to use separate plates for antibiotic testing.

But you could assess the amount of blood needed beforehand, couldn't you, so that you can do as much testing as needed (even when mistakes happen) without that the patient need to come back.

 2 years ago 

Patient sample is not limited to blood.

And for blood, only a few drops of diluted blood in broth is needed for each agar plate.

Thanks. I missed this point!