I presume your GP regards this as a chronic, and, as your husband seems to be well with little discomfort at the moment, a low-grade condition.
But the result needs to be acted upon, especially with the diabetes diagnosis.
The person to take advice from is not a general physician but the local consultant microbiologist at the hospital where the swab was sent. He/she will know the exact strain of MRSA and whether it is sensitive to any oral antibiotics. This could easily be done by telephone, so it would be worth asking your GP if this could be done.