Microbiology and Antimicrobial Susceptibility Patterns of Commensal Flora in the Middle Nasal Meatus

Objectives: We examined the microbiology and antimicrobial susceptibility patterns of commensal flora in the middle nasal meatus of normal subjects who were free of health care-associated risks and sinonasal disease. Methods: A prospective study was performed on 70 healthy volunteers without health care-associated risks or sinonasal disease. Middle meatal specimens were carefully taken by an endoscopically guided swab technique. The specimens were cultured for aerobic and anaerobic bacteria. Antimicrobial susceptibility testing was performed by the broth disc method. Results: Bacterial growths were recovered in 66 of the 70 specimens (94.3%). Coagulase-negative staphylococci (CNS) were the most common isolates (61.6%), followed by Staphylococcus aureus (11.6%) and Corynebacterium sp (9.3%). All growths were quantified as very rare (73.3%), rare (13.9%), or few (12.8%). Obligate anaerobic bacteria were not identified. The samples positive for CNS showed multiple resistances to antibiotics, including erythromycin stearate (30.2%), clindamycin hydrochloride (28.3%), oxacillin sodium (a clinical substitute for methicillin sodium; 18.9%), and sulfamethoxazole-trimethoprim (9.4%). Conclusions: A small amount of CNS with or without multiple antibiotic resistances and/or S aureus cultured from the middle meatus can be considered contaminants in middle meatal culture during an episode of rhinosinusitis.