My Husband Had MOHs Surgery On The Back Of His

My husband had MOHs surgery on the back of his ear two weeks ago and it turned into a mrsa infection. He is on sulfamethoxazole-Tmp ds 800-160 Tab and I change his dressing every day and was told to only use vaseline after cleaning the area. The wound now has a hole about 1/8 inch in diameter. I am very concerned as my husband is 85 years old. The dermatologist says the hole will close with the continued use of this antibiotic. She has done 3 cultures. Any ideas on what else to do to help him? It looks awful!