title: In vitro study of the inhibitory activity of usnic acid on dental plaque biofilm.
abstract: The vegetal extracts are used as an ecological alternative to classical anti-infectious treatments based on antibiotics, exhibiting the advantage of reduced secondary effects. Most of these compounds are secondary metabolites, especially aromatic substances synthesized by plants in a reduced concentration. The aim of this study was to investigate the influence of usnic acid against quorum sensing and response mechanisms involved in the initiation and development of the dental plaque biofilm and its tolerance to antimicrobials. Three samples of super-gingival dental plaque were treated for different time intervals with usnic acid at 200 ig/ml in dimethyl-sulfoxide, representing the MIC value. Each dental plaque sample was inoculated in Brain Heart Infusion medium to establish the microbial growing curve by viable cells counts using the tenfold microdilutions method. For strains identification there were used the microtest galleries: API 20Strep, API Staph, API 20NE, API 20E. MIC value for usnic acid was determined by twofold microdilution technique. Usnic acid selectively inhibited the biofilm development by Gram positive bacteria and the expression of haemolytic properties of strains isolated from the dental plaque. The growth curve of the isolated strains was affected by usnic acid, the changes consisting of the lag phase extension to 6-10 h (this time interval being considered as the persistence time of antimicrobial activity) and the significant decrease of the viable cell number and consecutively, the prolongation of the generation time. These effects are demonstrating the interference of the usnic acid with the intra- and interspecies signalling mechanisms based on quorum sensing and response and dependent on cell density, giving the possibility to use them as an active principle in some new pharmaceutical formula intended for the prevention and treatment of gingival and periodontal pathologies.
authors.affiliation: University of Bucharest, Faculty of Biology, Microbiology Immunology Department, Aleea Portocalelor, 1-5, Bucharest, Romania.
authors.forename: Mariana Carmen
authors.initials: MC
authors.lastname: Chifiriuc
authors.forename: Lia Mara
authors.initials: LM
authors.lastname: Diţu
authors.forename: Eliza
authors.initials: E
authors.lastname: Oprea
authors.forename: Sanda
authors.initials: S
authors.lastname: Liţescu
authors.forename: Marcela
authors.initials: M
authors.lastname: Bucur
authors.forename: Luminiţa
authors.initials: L
authors.lastname: Măruţescu
authors.forename: Gerard
authors.initials: G
authors.lastname: Enache
authors.forename: Crina
authors.initials: C
authors.lastname: Saviuc
authors.forename: Mihai
authors.initials: M
authors.lastname: Burlibaşa
authors.forename: Teodor
authors.initials: T
authors.lastname: Trăistaru
authors.forename: Gabriela
authors.initials: G
authors.lastname: Tănăse
authors.forename: Veronica
authors.initials: V
authors.lastname: Lazăr
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D001572:Benzofurans / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D003773:Dental Plaque / Q000382:microbiology*; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000254:growth & development; D006801:Humans; D008826:Microbial Sensitivity Tests; D053038:Quorum Sensing / Q000187:drug effects
chemical_list: D000890:Anti-Infective Agents; D001572:Benzofurans; C073339:usnic acid