If the bacteria isn't susceptible to the antibiotics given, the culture will be effective. Since the bacteria isn't dying with the antibiotics given to the snake, they are going to grow in the culture medium that doesn't have any antibiotic present. I'd still get a culture done. My vet thought it was a virus too, but it really want just a nasty, resistant bacteria.

My girl has been on antibiotics since 9/1, and I just sent off the culture this past Monday. Came back yesterday with what it was and what it is resistant, intermediate and susceptible to. Hopefully a change in antibiotics will do the trick. It was only intermediate to Baytril, which is what I have been using. So that's probably why she hasn't really been getting worse or better.

*sending lots of good luck to your snakie*