Yes a culture would have been more beneficial prior to treatment. What usually happens is the swab is taken and sent in to the lab for testing. The snake is generally started on a common treatment while waiting for the culture results just so the infection does not get worse. Then the meds are changed if necessary to better fit the final diagnosis once the test results come back.
Doing one now should still show what type of bacteria is present, but if the baytril is helping it may not matter.
My post was more meant to explain that if it is an abscess or tooth issue, it may not go away as quickly as RI or rot. Tooth issues often flare up more than once until the bad tooth comes out. I had this problem with one of my retics. Due to a broken tooth there was an abscess. It took 3 rounds of treatment during flare ups over the course of almost a year before the problem finally fixed itself. Their mouths are so sensitive that the smallest thing can cause an infection.