title: In vitro activity of antibiotic combinations against Pseudomonas aeruginosa biofilm and planktonic cultures.
abstract: In order to investigate the hypothesis that the combination of clarithromycin with other antibacterial agents offers a successful treatment in the eradication of Pseudomonas aeruginosa biofilm, we first determined the activity of eight antimicrobial agents against planktonic cultures of P. aeruginosa isolates by the microdilution technique. Second, we determined the in vitro effects of these antimicrobial agents individually and in combination against planktonic cultures and pre-formed biofilms of P. aeruginosa PA01. Drug combinations with marked activity were tested on biofilms of clinical isolates. The percentages of planktonic culture survival and biofilm persistence were determined using spectrophotometry and scanning electron microscopy, respectively. Bacterial enumeration was used as a more quantitative method to assess the viability of bacteria in the biofilm. Among the antibacterial agents tested, tobramycin and polymyxin B had the strongest activity against planktonic cultures when tested alone. Synergistic activity was observed for the combination chitosan/tobramycin against planktonic cultures but not biofilms, and for the combination tobramycin/clarithromycin against biofilms but not planktonic cultures. The results suggest that the combination clarithromycin/tobramycin may be successful for eradicating infections involving bacterial biofilms such as in cystic fibrosis patients chronically infected by P. aeruginosa. Further studies on representative isolates in vivo are warranted to support these results.
authors.affiliation: Pharmaceutical Microbiology Laboratory, Institute of Pharmacy, Université Libre de Bruxelles, CP 205/02, Boulevard du Triomphe, 1050 Brussels, Belgium. marie.tre-hardy@ulb.ac.be
authors.forename: Marie
authors.initials: M
authors.lastname: Tré-Hardy
authors.forename: Francis
authors.initials: F
authors.lastname: Vanderbist
authors.forename: Hamidou
authors.initials: H
authors.lastname: Traore
authors.forename: Michel Jean
authors.initials: MJ
authors.lastname: Devleeschouwer
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D017291:Clarithromycin / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000382:microbiology; D004338:Drug Combinations; D024881:Drug Resistance, Bacterial; D004357:Drug Synergism; D006801:Humans; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D011112:Polymyxin B / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000648:ultrastructure; D014031:Tobramycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D017291:Clarithromycin; D011112:Polymyxin B; D014031:Tobramycin