Microbiology: First stage and 2nd stage tests

BayernBlues

1. The problem statement, all variables and given/known data

I have some test results such as gram staining or urease tests to identify a bacteria. How do I figure out which tests are "first stage" tests and which ones are "second stage tests". Because based on the results of the test, I need to figure out which ones are needed and which ones aren't needed to identify the bacterium. I can't find any info on first or second tests and the difference between them. I know that the first test needed is gram staining which has determined that my bacterium is a negative gram stain (or pink) bacteria.