Subinhibitory concentrations ofmoxifloxacin decrease adhesion and biofilm formation of Stenotrophomonasmaltophilia from cystic fibrosis.

Stenotrophomonas maltophilia is an emerging nosocomial bacterial pathogen that is currently isolated with increasing frequency from the airways of cystic fibrosis (CF) patients. In this study the effect of subinhibitory concentrations (subMICs) of moxifloxacin on adhesion, biofilm formation and cell-surface hydrophobicity of two strains of S. maltophilia isolated from CF patients were evaluated. Adhesion and biofilm formation assays were carried out on polystyrene and quantified by colony counts. Cell-surface hydrophobicity was determined by a test for adhesion to n-hexadecane. Moxifloxacin at 0.03x and 0.06x MIC caused a significant decrease in adhesion and biofilm formation by both strains tested. A significant reduction in cell-surface hydrophobicity following exposure to subMICs of moxifloxacin was observed for one strain only. The results of the present study provide an additional rationale for the use of moxifloxacin in CF patients and more generally in biofilm-related infections involving S. maltophilia.