Super Bug that's Super Freaky

Almost a year ago my son developed really chapped lips along half of his bottom lip. The lip cracked in multiple places and then crusted over and spread down toward his chin. It looked awful and painful. We took him to the doctor where they started treating it just with aquafor, which did nothing. They then suspected impetigo and treated him for that, then a yeast infection, and after months of different treatment options we were referred to a dermatologist who put him on a steroid cream for two weeks. It cleared up the symptoms for the most part, yet returned within three days of stopping the cream. She put him back on the cream, which this time did nothing.

So, we go back to the doctor tomorrow as they are now suspicious that he may have MRSA (a bacterial super bug). They'll take a culture and we'll know for sure. At this point I just want to know what the heck it is and what treatment options will actually correct and fix the problem and not merely mask the symptoms. There has been talk of putting him on antibiotics for 40 days if it is in fact MRSA, which makes me nervous. He's been on antibiotics twice for pneumonia and both times it tore his stomach up. I try to avoid antibiotics at all cost so they don't build up an immunity (like declining it for ear infections that can clear on their own), but I know at this point he needs something and while I appreciate the doctors erring on the side of caution in his treatment, it seems like after 11 months of dealing with this they'd give him whatever it took to kill whatever he has.

I am tempted to just say, "I know you don't know what it is so just treat him for EVERYTHING you think it COULD be and hopefully one of your guesses will be right."