Pseudomonas aeruginosa tolerance to tobramycin, hydrogen peroxide and polymorphonuclear leukocytes is quorum-sensing dependent.
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.
Bjarnsholt
Thomas
T
Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Jensen
Peter Østrup
PØ
Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
Burmølle
Mette
M
Department of Microbiology, University of Copenhagen, DK-1307 Copenhagen K, Denmark.
Hentzer
Morten
M
Carlsberg Research Center, DK-2500 Valby, Denmark.
Haagensen
Janus A J
JAJ
Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Hougen
Hans Petter
HP
Institute of Forensic Medicine, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
Calum
Henrik
H
Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
Madsen
Kit G
KG
Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Moser
Claus
C
Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
Molin
Søren
S
Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Høiby
Niels
N
Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen Ø, Denmark.
Givskov
Michael
M
Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, DK-2800 Lyngby, Denmark.
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
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