The risk of development of antimicrobial resistance in individual patients with chronic rhinosinusitis.

OBJECTIVE To determine if individual patients with chronic rhinosinusitis (CRS) demonstrate an increasing prevalence of antimicrobial resistance over time. PATIENTS A prospectively maintained database of microbiologic culture results for adult patients with CRS was sequentially analyzed, extracting patients who underwent multiple serial sinus cultures over time. Antimicrobial resistance patterns were identified and quantified for each bacterium. Sequential culture results were compared for individual patients to determine if increasing overall bacterial resistance, gram-positive resistance, gram-negative resistance, or a shift toward gram-negative organisms was manifested within individual patients. RESULTS During a 7-year period, 90 adult patients were identified with 224 serial cultures (mean, 2.5 cultures per patient) obtained, with a median time between cultures of 157 days. Four hundred twenty-nine organisms were isolated from these serial cultures, consisting of 255 gram-positive organisms, 120 gram-negative organisms, 48 anaerobes, and 6 fungi. Pairwise analysis of sequential cultures revealed no significant trend toward increasing bacterial resistance within individual patients (P = .57, runs test). Similarly, no significant trend toward increasing gram-positive or gram-negative resistance was demonstrated. There was no shift toward gram-negative organisms (P>.15 for all). CONCLUSIONS Individual patients with CRS do not necessarily develop increasing levels of bacterial resistance over time. The use of culture-directed antimicrobial therapy may "protect" against the development of sequentially increasing antimicrobial resistance for patients with CRS.