My Husband Was Seen In The ER Friday Night For

My husband was seen in the ER Friday night for a really bad infection and a hard lump on his bottom. The ER doctor did a sonogram and said he thought it was MRSA. Then when he discharged him, he said he was putting it down as cellulitis because he couldn't be sure without a culture. While there, he was given antibiotics thru an IV and he is now on strong doses of antibiotics here at home. Is there a period of time after taking antibiotics that he is no longer contagious. The doctor did say that he was treating it like MRSA "just in case it was".