Brucella sp (tiny Gram negative coccobacilli) gram stain.
As part of our proficiency testing, accrediting bodies send us mystery samples to identify. In paper, they tell us they’re typical specimens, but in practice, they are always incredibly difficult to work through!
This one time, we were super stumped on this one organism. Everyone was smelling the plates (as an aside, “smell” the plates but don’t smell them, that’s dangerous) and throwing test after test at it. We had all of our microbiologists and a good chunk of the staff standing around huming and hawing over this and sniffing it for about a week.
We eventually realized it was Brucella abortus which should have been sent to the Level 3 lab and safely sealed away from day one when that indole didn’t go positive… any of the 6 times we did it.
Only one person got sick with it which is pretty impressive but still terrible.