Mupirocin is a topical antibiotic used to treat impetigo, a skin infection caused by Staphylococcus aureus, beta-hemolytic streptococcus, and Streptococcus pyogenes. Patients and certain healthcare workers use it intranasally (through the nose) to get rid of methicillin-resistant Staphylococcus aureus (MRSA) that has colonized the nose.