Can you describe his habitat? What kind of enclosure, how are you heating it, and how are you regulating the heat? What kind of substrate were you using when you first noticed the problem, and is this snake now in a minimal environment that is easy to clean and disinfect?
Ceftazidime (Fortaz) is one of the big gun antibiotics for reptiles. It hasn't been in use nearly as long as Baytril so there fewer (not zero) issues with resistant bacteria.
Not sure about in Canada but in the US you need a prescription for silvadene (silver sulfadiazine), except for one online store I found will sell it without. Highly recommended for burns.