I am not experienced in diagnostic bacteriology and am interested in understanding more about it in the context of analyzing food purity.
For example, imagine I have a supply of raw milk which might be, for example, a 20 gallon tank. I would like to ensure that listeria, e. coli and salmonella are not present in the milk.
Is it sufficient to take a single drop of the milk and examine it under a microscope or do I have to do more extensive sampling, for example, sampling every inch vertically or something like that?
What is the procedure to make sure my milk is free of the bacteria, or is that impossible?
I am not interested in procedures to kill the bacteria. I know those. I want to understand the diagnostic processes to tell if bacteria is there.