Corticosteroids directly reduce Staphylococcus aureus biofilm growth: an in vitro study

Clinical improvement in patients with chronic rhinosinusitis (CRS) treated with steroids alone has previously been ascribed to the steroids' anti-inflammatory properties rather than any direct effect on the bacteria. The aim of this study was to determine if commonly used intranasal steroids directly reduce bacterial biofilm production in vitro.

In vitro comparative controlled trial.

Staphylococcus aureus biofilms were grown on minimum biofilm eradication concentration device pegs and treated with the commonly prescribed CRS topical steroids fluticasone, mometasone, or budesonide. These were dissolved in vehicle solvents and added to cerebrospinal fluid (CSF) broth. Concentrations (including therapeutic doses) tested for fluticasone and mometasone ranged from 25 μg/200 μL to 400 μg/200 μL, and from 16 μg/200 μL to 2000 μg/200 μL for budesonide. Control pegs were exposed to equivalent volumes of the appropriate solvent/CSF broth. Confocal scanning laser microscopy and COMSTAT software were used to quantify biofilms at 24 hours after treatment.

Significant differences from control were found for fluticasone at 400 μg/200 μL (difference = -0.3065 μm(3)/μm(2), P = .007), mometasone at 300 μg/200 μL and 400 μg/200 μL (difference = -0.15 μm(3)/μm(2), P = .006, and difference = -0.9193 μm(3)/μm(2), P = .034, respectively), and budesonide at 750 μg/200 μL, 1000 μg/200 μL and 2000 μg/200 μL (difference = -1.0137 μm(3)/μm(2), P = .038, difference = -0.6164, P = .009, and difference = -0.1906 μm(3)/μm(2), P = .029, respectively).

The concentrations of 400 μg/200 μL of fluticasone, 300 μg and 400 μg/200 μL of mometasone, and 750 μg, 1,000 μg, and 2,000 μg/200 μL of budesonide directly reduce biofilm production in vitro, outside of the inflammatory milieu.