If you do not choose to biopsy, and while waiting for the culture and sensitivity results, your vet could try treating your cat with
prednisolone, vitamin E, and with
the antibiotic Zithromax. The prednisolone and vitamin E would be for the auto-immune part of the disease and the Zithromax should cover the secondary bacterial infection. Zithromax is excellent for upper respiratory infections and it also is effective against Bartonella.