Wow I can't believe fogging her hasn't cured it! Are you fogging her like Brian from BHB does?
I think getting a culture done and giving her the right injection is your last resort. I agree completely with your comment about your vet and him telling you things without actually knowing. They have a place much like a forum with vets and pharm reps where they can get advice. That's what my vet does and she is very open to input from breeders. My sister is planning to become a vet so she has been able to do a lot of job shadowing and confirmed the forum thing.