D.W.
It sounds like your doctor has prescribed the best treatment so far.
Obviously, you'll want to stop using the diapers.
Johnson and Johnson is rigorously defending the diapers despite the uproar. I've never been a Pampers fan personally, so we haven't been affected.
But, our daughter was diagnosed with MRSA (a serious staph infection because it's resistant to methicillin) last week. She's not on Bactrim, but she's been responding well to Bactriban 3 times/day for the past week.
Good luck!