That's what I don't understand....unless it was intentionally "planted." Or, it is originating with a supplier.
Sounds like sabotage to me too.
“Do you think it’s weird that the bacteria exists in plants in three different states?”
I have no inside information, but it could be a process thing...something like “steam-clean all vats and machinery for 10 minutes at the end of each shift”. Some new guy comes in at the head of the department that oversees that process - perhaps a Harvard-education Constitutional Scholar, for example, and has been taught to “think outside the box”. So he starts asking questions and no one can remember why they need to clean them out after each shift - so he changes the frequency to once per day, and for a long time they get away with it...and then they learn their lesson.
That’s one possibility. I think planting would be tougher because it was found at the 3 plants. Suppliers maybe, but there’s a good chance that suppliers work with more than one company.