What Does High Fever After Knee Replacement Surgery Indicate?

My husband had a knee replacement in June, 2014. He was doing really well until suddenly he came down with an extremely high fever and pain in the knee..the hospital diagnosed him with a staff infection and his knee was full of pus. The surgeon flushed it out but a few days later he was back in the hospital and they put a temporary knee in to remove the source of the infection in his body. He is still running a high fever and he is on IV antibiotics. Unfortunately I don t know the name of the antibiotic but his mother is insisting that doxicillin is the ONLY thing that will help him. The staff infection is also in his intestines. I do know that the antibiotic he is on starts with a p...I need to know if doxicillin is still used and how effective it is, and maybe you can guess what antibiotic he IS on so I can shut her up about how the surgeon is treating his infection. And will it, or can it, move up further to his chest?