First question,

Do you know how to diagnose a snake with an RI? My first concern was that you said you saw the snake take a drink of water... and it drooled.

So you decided the snake has an RI and start medicating it?

Sorry dude, the snake drooled after drinking water, which is not uncommon...

Your vet should still now how to do a culture, even if they are not up to date with the anatomy of this species and how it should look rightfully.

Bloods will have a pronounced spine like others have said, if you can't see the spine easily, the animal is likely too fat. Bloods are more upright oval shaped, whereas balls are more rounded triangle shaped. If that makes sense. Your's does not look emaciated at all.

Stop giving the animal meds until you get a culture from a vet. It is easy to overdo meds, especially if the animal is not sick, you'd just end up burning up their liver and potentially creating bacterial resistance.