My 3-legged cat is getting UTIs  

My 2yo 3 legged cat (missing back right) is developing UTI's. I'm wondering why it's recurring. We got her sanitary shave and been on top of cleaning the cat box. I wonder if this is just a thing, or what I can do to prevent it. I'm trying to find a non prescription dry food and I found some articles about the better wet foods. Plus sanitary shaves and I guess just being more on top of the cat box. I've heard of supplements but I don't even know what would be best. Very niche cat problem...