Dianne, please contact your Dad's doctor rather than "popping" in antibotics in at random. I've had four infections since December, and they've been taken very seriously. I spent five days in hospital on IV antibiotics for the first one, and for the next two I was taking Flagyl and Cipro four times a day.
The source of the infection is not necessarily the stent. In fact, despite doing CT scans on each occasion, they haven't really pinpointed the source of mine, and I have an appointment with an infectious disease specialist next week to see if he can get to the bottom of it. Also, my medical oncologist has decided that the risk of sepsis is too great to continue with chemotherapy.
I hope your Dad's doctor can get to the bottom of this. My infections made me feel absolutely wretched, and each time it seems to take longer to claw myself back.