title: Pseudomonas aeruginosa tolerance to tobramycin, hydrogen peroxide and polymorphonuclear leukocytes is quorum-sensing dependent.
abstract: The opportunistic human pathogen Pseudomonas aeruginosa is the predominant micro-organism of chronic lung infections in cystic fibrosis (CF) patients. P. aeruginosa colonizes the CF lungs by forming biofilm structures in the alveoli. In the biofilm mode of growth the bacteria are highly tolerant to otherwise lethal doses of antibiotics and are protected from bactericidal activity of polymorphonuclear leukocytes (PMNs). P. aeruginosa controls the expression of many of its virulence factors by means of a cell-cell communication system termed quorum sensing (QS). In the present report it is demonstrated that biofilm bacteria in which QS is blocked either by mutation or by administration of QS inhibitory drugs are sensitive to treatment with tobramycin and H2O2, and are readily phagocytosed by PMNs, in contrast to bacteria with functional QS systems. In contrast to the wild-type, QS-deficient biofilms led to an immediate respiratory-burst activation of the PMNs in vitro. In vivo QS-deficient mutants provoked a higher degree of inflammation. It is suggested that quorum signals and QS-inhibitory drugs play direct and opposite roles in this process. Consequently, the faster and highly efficient clearance of QS-deficient bacteria in vivo is probably a two-sided phenomenon: down regulation of virulence and activation of the innate immune system. These data also suggest that a combination of the action of PMNs and QS inhibitors along with conventional antibiotics would eliminate the biofilm-forming bacteria before a chronic infection is established.
authors.affiliation: Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bjarnsholt
authors.affiliation: Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Peter Østrup
authors.initials: PØ
authors.lastname: Jensen
authors.affiliation: Department of Microbiology, University of Copenhagen, DK-1307 Copenhagen K, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Burmølle
authors.affiliation: Carlsberg Research Center, DK-2500 Valby, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Hentzer
authors.affiliation: Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Janus A J
authors.initials: JAJ
authors.lastname: Haagensen
authors.affiliation: Institute of Forensic Medicine, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Hans Petter
authors.initials: HP
authors.lastname: Hougen
authors.affiliation: Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Calum
authors.affiliation: Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Kit G
authors.initials: KG
authors.lastname: Madsen
authors.affiliation: Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Claus
authors.initials: C
authors.lastname: Moser
authors.affiliation: Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Molin
authors.affiliation: Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Høiby
authors.affiliation: Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D003550:Cystic Fibrosis / Q000382:microbiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009504:Neutrophils / Q000276:immunology*; D011552:Pseudomonas Infections / Q000276:immunology / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity*; D015398:Signal Transduction; D014031:Tobramycin / Q000494:pharmacology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C080365:LasR protein, Pseudomonas aeruginosa; C086515:RhlR protein, Pseudomonas aeruginosa; D015534:Trans-Activators; D006861:Hydrogen Peroxide; D014031:Tobramycin