Why perform multiple tests in order to identify an unknown bacterium, instead of a single biochemical test

There is no specific test available for a perticular or any individual bacterium to be identified. A prticular test can only narrow down the choices on the basis of characteristic each test excludes or includes.

Most of the time, to identify a particular bacterium atleast 3 to 4 tests are required. Each test can give postive result to be positive for a new group of bacteria.