Sadly, we deal with MRSA infections regularly as well. I feel your pain! Brandyn has been on and off bactrim since he was about 8 months old.
I'm probably not going to tell you anything that you don't already know since you have been to an infectious disease specialist but here it goes
Bleach all clothing, bedding, toys, etc. and use hot water.
Bleach baths (we don't do this currently as Brandyn drinks the bath water!)
Hibiclens wash on his scalp which is where he gets the infections and erythromycin eye ointment because he gets the pustules on his eyelids too.
We use gloves when applying his creams- change them for different areas of the body.
Antibacterial wipes to clean everything.
Bactroban ointment on individual pustules as a first line of defense to try and avoid antibiotics and in the nose of all family members.
My husband and I have done rounds of decolonization but we can't do that with brandyn as the treatment is too harsh-daily washes with hibiclens and bactroban in our noses. I think it's somewhat pointless as we are probably decolonized for a little while but since he is colonized we get recolonized.
Brandyn had two episodes of MRSA septacemia while he was in the NICU but luckly even though he is colonized it hasn't gone into his blood since. I have received conflicting advice. Some doctors are against using bactrim at the first sign of infection and others say it's ok. I guess some kids with severe eczema have to be on bactrim often so one dermatologist said not to worry.
Our current dermatologist says that this won't be a problem as he gets older..
I hope that the above has helped, even if it's just a little! My e-mail is firstname.lastname@example.org and you more than welcome to e-mail me anytime