Hi L.,
Have you tried Zymox? It helped my dog who had chronic ear infection and nothing else worked. It contains enzymes found in raw milk - so if you have access to raw milk, you might try that. (don't use pasteurized milk - it would make it worse). Here's a source:
http://www.calvetsupply.com/index.asp?PageAction=VIEWPROD...
I also suggest dietary support that boosts the adrenals and the immune system. Research a raw diet for cats - I make my own cat food using the recipe at catnutrition.org - they love it. Also, just adding a little yogurt and some raw meat to their commercial cat food may help.
I also put some finely diced garlic in their food, and cod liver oil.
I'm no expert nor a vet, but I don't have to take my animals to the vet unless they get in a fight. They never get sick anymore - and it's been 4 years for cats, 8 years for dog.
Hope this helps,
-B.