If there was any ONE thing, it would be SO easy. A combination of things including the cat's gene pool all contribute to a UTI.

Donna was right to suggest some canned / wet food in the diet. You don't want ALL canned, as then you get tooth decay. But you want to encourage moisture intake.

I chose to do that by getting a water fountain. There are many types out there. I bought the Fresh Flow. Of course, with 9 cats, buying a foutain and running that will be easier than randomly mixing in canned foods and hoping everyone gets some of it.

Here is just one of many articles you can find on the subject. I googled: feline uti

http://searchwarp.com/swa26640.htm