Microbiology of the ethmoid sinus following endoscopic sinus surgery.

We prospectively studied the native microbiology of the ethmoid sinus following endoscopic sinus surgery in 113 patients (mean age: 41.3 yr). After each patient had regained complete mucosalization (minimum follow-up: 6 wk), we obtained a bacterial swab of the ethmoid sinus and submitted it for culture and sensitivity analysis. We then compiled data on sensitivity patterns and the number and type of bacteria isolated. Of the 113 patients, 67 (59.3%) had positive cultures, 26 (23.0%) had sterile cultures, and 20 (17.7%) had normal flora. Multiple bacteria were isolated in 31 of the 113 patients (27.4%). The most common isolates were gram-positive cocci, and the most common bacteria were staphylococcal species. A significant degree (42.9%) of beta-lactamase resistance was exhibited. We conclude that the ethmoid sinus is not microbiologically sterile following endoscopic sinus surgery.