It's Amikacin! And your vet is doing all he can since you didn't want to get the culture done.

A proper culture is SENT OFF to a lab, which takes less than a week, and will tell the vet what bacteria it is and what antibiotics that bacteria is sensitive or resistant to. A culture cannot be done at the vet office. All he did was get a sample of the mucous and look at it under the microscope. That is not a culture.. Cultures involve petri dishes, incubation and looking at what bacteria colonies grow.

Baytril needs to be injected. Oral antibiotics DO NOT work since their metabolisms are so slow. Oral only works if that antibiotic only comes in oral form(such as trimethoprim sulfamethoxazole- bactrim).

I would get the culture done, get the snake's temperatures up to 95-97 on the hot side, 85-87 on the cool side, and around 75% humidity, just to keep him comfortable until the culture comes back. THEN the vet can put him on the proper antibiotic injections so he can get well.