C. Study design and research methods: A nasal swab will be obtained just prior to initiation of mupirocin therapy, within 48 hours of the completion of mupirocin therapy, one week, two weeks, four weeks, eight weeks, and 16 weeks following the completion of mupirocin therapy. The swab will be inserted into one nare and rotated for 3 seconds. The procedure will be repeated on the other nare. The two heads will be refrigerated immediately, and held at 2-5o C until they can be placed into sterile micro tubes for storage at -80o C. A separate swab will be passed through the mouth and rubbed over the tonsils and posterior oropharynx , and stored in the same fashion.