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Purpose: The aim of the present study was to examine whether xylitol, at different concentrations, inhibits the formation of an experimental model of oral biofilm.Materials and Methods: Biofilms of six bacterial species (Streptococcus mutans, Streptococcus sobrinus, Lactobacillus rhamnosus, Actinomyces viscosus, Porphyromonas gingivalis and Fusobacterium nucleatum) were prepared on hydroxyapatite (HA) discs according to the Zürich Biofilm Model. Xylitol was tested at two concentrations, 1% and 3%. At the end of their designated incubation times, some HA discs were destined for confocal laser scanning microscopy (CLSM) and the others were harvested using a sterile surgical instrument. Aliquots of harvested biofilms were diluted and plated onto specific media. After a 48-h anaerobic incubation at 37 degrees C, the colony-forming units (CFUs) were counted.Results: CLSM images showed that only a small amount of isolated bacteria was observed on the surface of HA discs. Culture of harvested biofilms showed an inhibition in the growth of different species included in the biofilms.Conclusions: Xylitol has a clear inhibitory effect on the formation of the experimental biofilms. This study shows that xylitol is not only efficient in inhibiting the acid production of cariogenic bacteria, but also in preventing the formation of a multispecies biofilm; it confirms the relevance of the use of this polyol for the prevention of oral diseases caused by dental plaque. [ABSTRACT FROM AUTHOR]

The discovery of quorum sensing (QS) communication systems regulating bacterial virulence has afforded a novel opportunity for controlling infectious bacteria by interfering with QS. Pseudomonas aeruginosa is an example of an opportunistic human pathogen for which N-acyl homoserine lactone (AHL)-related compounds have been described as potent inhibitors of biofilm formation and virulence factors, given their similarity to the natural QS autoinducers (AHLs). Our purpose was to design potent analogs of N-butanoyl-l-homoserine lactone (C4-HSL) and to screen them for biological activity. Eleven original compounds characterized by the modification of the lactone moiety were screened for their ability to impair biofilm formation. Among them, compound 11 was able to modify the growth kinetics and to restrict the number of adherent cells when added from the early stages of biofilm formation (i.e., adhesion and microcolony formation) in a dose-dependent manner. To demonstrate antagonism with C4-HSL, we showed that the inhibition of biofilm formation by compound 11 was impaired when C4-HSL was added. Structure-activity relationships are discussed with respect to the results obtained. La découverte du quorum sensing (QS), système de communication régulant la virulence bactérienne, permet une nouvelle approche dans le contrôle des infections bactériennes en interférant avec ce système. Pseudomonas aeruginosa est un exemple de bactérie pathogène opportuniste pour laquelle les composés de type N-acyl homosérine lactones (AHLs) ont été décrits comme des inhibiteurs potentiels de la formation de biofilm et de l’expression des facteurs de virulence, compte tenu de leur similitude avec les auto-inducteurs naturels impliqués dans le QS. Notre objectif était de concevoir des analogues de la N-butanoyl-l-homosérine lactone (C4-HSL) et de les cribler pour leur activité biologique. Onze analogues originaux, caractérisés par des modifications du cycle lactone, ont été synthétisés puis évalués pour leur capacité à inhiber la formation du biofilm. Parmi ces analogues, le composé 11 induit des modifications de la cinétique de formation du biofilm et réduit le nombre de cellules adhérées s’il est présent dès les premières étapes de formation du biofilm (adhésion et formation des micro-colonies); l’effet observé est dépendant de la dose. Afin de confirmer l’antagonisme avec la C4-HSL, nous avons montré que l’inhibition de la formation du biofilm par le composé 11 était réduite lors de l’addition conjointe de la C4-HSL. Pour finir, les relations structure-activité sont discutées en fonction des résultats obtenus. [ABSTRACT FROM AUTHOR]