A culture should have been done. Oral swabs are ok, but a lung wash really is the definitive test. There is a problem after treating with antibiotics cultures are skewed and the value of the results are seriously reduced.

Strictly oral is limited in its use. That said the new studies being done are suggesting a short round of injected antibiotics followed by long round of oral dosing. I am waiting on the actual papers on this but a good friend came back from the vet conference in Florida a couple of moths back and this is where she heard this info in a symposium with Dr. Mader. This is very new ideas however. It is more likely your vet is treating a snake like a small mammal.