title: Quorum sensing and virulence of Pseudomonas aeruginosa during lung infection of cystic fibrosis patients.
abstract: Pseudomonas aeruginosa is the predominant microorganism in chronic lung infection of cystic fibrosis patients. The chronic lung infection is preceded by intermittent colonization. When the chronic infection becomes established, it is well accepted that the isolated strains differ phenotypically from the intermittent strains. Dominating changes are the switch to mucoidity (alginate overproduction) and loss of epigenetic regulation of virulence such as the Quorum Sensing (QS). To elucidate the dynamics of P. aeruginosa QS systems during long term infection of the CF lung, we have investigated 238 isolates obtained from 152 CF patients at different stages of infection ranging from intermittent to late chronic. Isolates were characterized with regard to QS signal molecules, alginate, rhamnolipid and elastase production and mutant frequency. The genetic basis for change in QS regulation were investigated and identified by sequence analysis of lasR, rhlR, lasI and rhlI. The first QS system to be lost was the one encoded by las system 12 years (median value) after the onset of the lung infection with subsequent loss of the rhl encoded system after 17 years (median value) shown as deficiencies in production of the 3-oxo-C12-HSL and C4-HSL QS signal molecules respectively. The concomitant development of QS malfunction significantly correlated with the reduced production of rhamnolipids and elastase and with the occurrence of mutations in the regulatory genes lasR and rhlR. Accumulation of mutations in both lasR and rhlR correlated with development of hypermutability. Interestingly, a higher number of mucoid isolates were found to produce C4-HSL signal molecules and rhamnolipids compared to the non-mucoid isolates. As seen from the present data, we can conclude that P. aeruginosa and particularly the mucoid strains do not lose the QS regulation or the ability to produce rhamnolipids until the late stage of the chronic infection.
authors.affiliation: Institute for International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bjarnsholt
authors.forename: Peter Østrup
authors.initials: PØ
authors.lastname: Jensen
authors.forename: Tim Holm
authors.initials: TH
authors.lastname: Jakobsen
authors.forename: Richard
authors.initials: R
authors.lastname: Phipps
authors.forename: Anne Kirstine
authors.initials: AK
authors.lastname: Nielsen
authors.forename: Morten Theil
authors.initials: MT
authors.lastname: Rybtke
authors.forename: Tim
authors.initials: T
authors.lastname: Tolker-Nielsen
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Niels
authors.initials: N
authors.lastname: Høiby
authors.forename: Oana
authors.initials: O
authors.lastname: Ciofu
mesh_terms: D003550:Cystic Fibrosis / Q000150:complications*; D005798:Genes, Bacterial; D006017:Glycolipids / Q000032:analysis; D006801:Humans; D008171:Lung Diseases / Q000382:microbiology*; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology*; D053038:Quorum Sensing / Q000235:genetics*; D013997:Time Factors; D014774:Virulence / Q000235:genetics
chemical_list: D006017:Glycolipids; C418382:rhamnolipid
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