Have irritated perianal area like a diaper rash-got call from derm saying culture + for staphylococcus/no yeast or fungus- would it have said if mrsa?

Bacterial Culture: Yes, the culture would have told the doctor if you had mrsa.

Yes: One would think so. There are staph infections that are not methicillin resistant (mrsa).

Maybe: Mrsa means that the staphylococcus is resistant to multiple antibiotics. If a sensitivity to antibiotics was done, then the doctor should have told you which one would work and if it is the one prescribed or not. A sensitivity may or may not have been done. It does cost extra for that service by the lab.