What does the infection look like? Is it crusty, feels rough, itchy, red, pus? etc.? Does he have a high fever?
The mupirocin is a good idea but the steroid ointment use very sparingly. A very very thin amount of steroid. You may want to try to use only the mupriocin then the steroid of and on for a few days.
I wouldn't worry so much about a topical. The only other things are honey, chlorhexadine and 3% hydrogen peroxide. I would try to not touch it very much because you can easily spread it around. Be sure to wash your hands well and any the water handles with a disinfectant and the towels you use.
mkh9