I bought a house not realizing that many cats had lived there for quite a while. When we visited the house prior to purchase the seller had candles burning, cookies baking in the oven and a couple windows open.

I tried the above suggestions, but what worked the best is that product hyped on TV. Oxiclean. They now have a liquid version, but I used the powder mixed with water. It is the only product that got the cat odor out of tile grout.