Subinhibitory concentrations of moxifloxacin decrease adhesion and biofilm formation of Stenotrophomonas maltophilia from cystic fibrosis

1 Clinical Microbiology Unit, Department of Biomedical Sciences, ‘G. D’Annunzio’ University of Chieti-Pescara, Chieti, Italy 2 Center for Excellence on Aging, ‘G. D’Annunzio’ University Foundation, Chieti, Italy 3 Clinical Microbiology and Virology Unit, Department of Transfusion Medicine, ‘Spirito Santo’ Hospital, Pescara, Italy 4 Laboratory of Clinical Microbiology, ‘Bambino Gesù’ Pediatric Hospital, Rome, Italy Correspondence G. Di Bonaventura gdibonaventura{at}unich.it Received April 23, 2009 Accepted September 16, 2009 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 0.03 x and 0.06 x 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 .