How is it possible for the same species to have two or more identification codess with the enterotube?

Answer 1

Not all bacteria of a given species will produce the same result in a given test media. For example, according to Bergey's, somewhere between 11% and 89% of E. coli are positive for ornithine decarboxylase. Since this test is inconclusive either a positive or negative result is acceptable if other tests indicate that the species being tested is E. coli.

Answer 2

In any population of a species, there is a certain amount of variability. The bacterial ID numbers refer to specific biochemical reactions in the specific individual organism tested.