Have had a leg abscess 3 times since last November. Why does it keep coming back?

Pretty sure it was caused by my indoor cat scratching me and although I have been to see 3 doctors and taken numerous antibiotics it's back again. Very painful. Why would it keep coming back after it seems to heal each time? I took all of my antibiotics faithfully. What type of bacteria from a cat would cause this? Thanks to all who answer.