title: Biofilm formation by Stenotrophomonas maltophilia: modulation by quinolones, trimethoprim-sulfamethoxazole, and ceftazidime.
abstract: We investigated the in vitro effects of seven fluoroquinolones (ciprofloxacin, grepafloxacin, levofloxacin, moxifloxacin, norfloxacin, ofloxacin, and rufloxacin), compared to those of trimethoprim-sulfamethoxazole (SXT) and ceftazidime on total biomass and cell viability of Stenotrophomonas maltophilia biofilm. S. maltophilia attached rapidly to polystyrene, within 2 h of incubation, and then biofilm formation increased over time, reaching maximum growth at 24 h. In the presence of fluoroquinolones at one-half and one-fourth the MIC, biofilm biomass was significantly (P < 0.01) reduced to 55 to 70% and 66 to 76% of original mass, respectively. Ceftazidime and SXT did not exert any activity. Biofilm bacterial viability was significantly reduced by all antibiotics tested at one-half the MIC. At one-fourth the MIC all antibiotics, except levofloxacin, significantly reduced viability. Treatment of preformed biofilms with bactericidal concentrations (500, 100, and 50 micro g/ml) of all fluoroquinolones caused, except for norfloxacin, significant reduction of biofilm biomass to 29.5 to 78.8, 64.1 to 83.6, and 70.5 to 82.8% of original mass, respectively. SXT exerted significant activity at 500 micro g/ml only. Ceftazidime was completely inactive. Rufloxacin exhibited the highest activity on preformed biofilm viability, significantly decreasing viable counts by 0.6, 5.4, and 17.1% at 500, 100, and 50 micro g/ml, respectively. Our results show that (i) subinhibitory (one-half and one-fourth the MIC) concentrations of fluoroquinolones inhibit adherence of S. maltophilia to polystyrene and (ii) clinically achievable concentrations (50 and 100 micro g/ml) of rufloxacin are able to eradicate preformed S. maltophilia biofilm.
authors.affiliation: Dipartimento di Scienze Biomediche, Laboratorio di Microbiologia Clinica, Università G. D'Annunzio Istituto per i Trapianti d'organo e Immunocitologia, Consiglio Nazionale delle Ricerche, Sezione di Chieti, Chieti, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Bonaventura
authors.forename: Ilaria
authors.initials: I
authors.lastname: Spedicato
authors.forename: Domenico
authors.initials: D
authors.lastname: D'Antonio
authors.forename: Iole
authors.initials: I
authors.lastname: Robuffo
authors.forename: Raffaele
authors.initials: R
authors.lastname: Piccolomini
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects*; D002442:Ceftazidime / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D015363:Quinolones / Q000494:pharmacology*; D020615:Stenotrophomonas maltophilia / Q000187:drug effects* / Q000254:growth & development* / Q000648:ultrastructure; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology*
chemical_list: D000890:Anti-Infective Agents; D002511:Cephalosporins; D015363:Quinolones; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D002442:Ceftazidime