Ds had a staph infection on his bum last winter. Ped. cultured it, wasn't MRSA. She thought it could be MRSA because the biggest boil had come to a head. I had mentioned that dd had a recurring spot on her arm, but it never came to a head. She said she didn't think it was MRSA because it DID NOT come to a head. So, I guess MRSA usually will come to a head. BTW, she told us to drain ds's boil and we had him soak in a warm bath. It drained by itself in there. We treated with bactroban cream and it was significantly better within 12 hours.
I know how you're feeling. Thinking your child has MRSA, and that you can be in that cycle for a long time is so stressful! I was really, really scared. My ped is awesome, though and she really put me at ease about it. Good luck with all this, and please keep us posted.