that is great you know a vet, she sure will have all that stuff, any broad spectrum a/b that she'd use for dog/cat would work for a frog, you don't need much, just a few drops (2-3 if a frog is small) on a back once a day for 10 days in a row, if she could give you like 1ml of a/b that would be more then enough and ask for flamazine, it is also used for dogs/cats and actually i like to use it for kids too that would be the best way to do it.

if you are using melafix make sure you use a/b cream ( neosporine, polysporine, etc without painkillers) for whatever you see damaged.