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

ABSTRACT

OBJECTIVES/HYPOTHESIS: 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. STUDY DESIGN: In vitro comparative controlled trial. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.