Increased antibiotic resistance of isolates from chronic rhinosinusitis patients grown in anaerobic conditions.

Introduction: In chronic rhinosinusitis (CRS), the congestion and blockage of the nose can cause anaerobic conditions within the sinus cavities which may promote the expression of virulence and antibiotic resistance genes in invading pathogens. is a facultative anaerobic bacteria and causes severe recalcitrant CRS. In this study, we aimed to evaluate the antimicrobial resistance of isolates of CRS patients in planktonic and biofilm form grown in aerobic and anaerobic conditions.

Methods: clinical isolates of CRS patients ( = 25) were grown in planktonic and biofilm form in aerobic and anaerobic conditions. Minimum inhibitory concentrations (MIC) of planktonic forms and minimum biofilm eradication concentrations (MBEC) were determined. Additionally, metabolic activity by fluorescein diacetate assay, biofilm biomass by crystal violet assay and eDNA concentration were assessed in both conditions.

Results: planktonic cells grown in anaerobic condition exhibited increased gentamicin resistance ( < .01), whereas biofilms grown in anaerobic condition displayed significantly increased MBEC values for gentamicin ( < .0001) and levofloxacin ( < .001). The metabolic activity of anaerobic biofilms was significantly higher compared with aerobic biofilms ( < .0001). However, the biofilm biomass of isolates grown in aerobic conditions was higher than anaerobic conditions ( < .5).

Conclusion: isolates from CRS patients grown in anaerobic conditions showed significantly increased resistance to antibiotics with an increased metabolic activity but decreased biofilm biomass.

Level Of Evidence: NA.