Bacteriology of the sinus cavities of asymptomatic individuals after endoscopic sinus surgery

Objective: To determine the resident flora and the level of bacterial presence of the healthy sinus cavity post-endoscopic sinus surgery (ESS). Setting: University-based prospective trial. Method. Subjects included asymptomatic patients who had undergone ESS for inflammatory disease more than 12 weeks previously. Endoscopic cultures of the sinus cavities were performed with swab and a novel lavage technique and were processed for identification of bacterial species and the level of bacterial presence. Results: Thirty-two patients were recruited. Bacterial organisms were recovered in 97% of subjects (mean 1.5 organisms/patient). The flora predominantly consisted of coagulase-negative staphylococci (69%) and diphtheroids (25%). Staphylococcus aureus was recovered in 31% of subjects and Pseudomonas aeruginosa in 3% only. No gram-negative rods were recovered in any individual. The Gram stains of 29 individuals were identified; 20 (69%) had no white blood cells, 9 (31%) had 1+ white blood cells, and none had > 1 white blood cells. All quantitative lavage fluid cultures were negative at the 104 detection level. Conclusion: Coagulase-negative staphylococci, diphtheroids, and S. aureus constitute the predominant flora of the healthy post-ESS sinus cavity and probably represent colonization of the cavity by nasal flora from the contiguous nasal mucosa. These data offer a basis for interpreting sinus cultures obtained in symptomatic patients after ESS. S. aureus may be frequently recovered in asymptomatic patients; thus, not all instances of S. aureus recovery on culture require therapy. Future testing of individuals with this organism will probably have to be modified to better assess factors associated with pathogenicity, such as bacterial load, biofilm formation, or superantigen production. In contrast, gram-negative rods and P. aeruginosa should probably be treated when identified on culture.