Maybe it's just me but that looks pretty bubbly at the back of the throat. If you had a culture done and it was good, then I don't know. How well do you trust this vet? Maybe find another exotic vet and call them and find out their experience with reptiles and maybe get a culture done with them?
My vet always does cultures and really doesn't like to throw antibiotics at my reptiles unless they are really sick which in that case she will prescribe a wide spectrum one until the culture comes back and then switch if needed. I trust her though as she saved Allie from dying from PAM and has treated Rosey for a sinus infection and Harley for RI.