Molecular analysis of methicillin-resistant Staphylococcus aureus as a causative agent of bronchopulmonary infection: relation to colonization in the upper respiratory tract.

Using five diagnostic markers, we compared the types of 72 strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated simultaneously from the nasal cavity, pharynx, and sputum from 24 patients. Almost identical MRSA types had colonized the nasal cavity and sputum from the same patient for 21 (88%) of the patients. We speculate that most MRSA organisms isolated in sputum are derived from the nasal cavity, while a few are derived from the pharynx.