Objectives/hypothesis: The objective was to determine whether infections occurring after endoscopic sinus surgery represent overgrowth of sinonasal flora versus de novo bacterial infection.
Study design: Prospective controlled cohort study.
Methods: A cohort of adult patients was prospectively followed after endoscopic sinus surgery. Baseline postoperative control cultures of the ethmoid sinus were obtained. Patients with acute infectious exacerbations of chronic rhinosinusitis had endoscopic culture, and these results were compared with baseline culture data.
Results: One hundred thirteen patients were followed for a mean period of 14.5 months after endoscopic sinus surgery. Baseline postoperative culture data revealed that the ethmoid labyrinth was sterile in 23% of cases, carried oral flora in 18% of cases, and was colonized in 60% of cases. Gram-positive cocci, particularly staphylococcal species, were the most common colonizing organisms (41% of cases). Twenty acute exacerbations were cultured in 17 patients during the follow-up period. All infectious cultures recovered bacteria; one culture recovered only oral flora. Gram-positive cocci predominated (56% of isolates) with Staphylococcus aureus being the most common isolate (28%). Of the 36 isolates, only 9 isolates (25%) corresponded to bacteria identified at the time of baseline culture.
Conclusion: Although the postoperative sinonasal cavity may be colonized by bacteria after endoscopic sinus surgery, infections arising postoperatively most commonly represent de novo infections by bacteria other than colonizing bacteria. Empirical therapy based on baseline data may be misleading; acute exacerbations of chronic rhinosinusitis after endoscopic sinus surgery should be cultured to guide optimal antibiotic therapy.