title: N-Acetyl-l-cysteine effects on multi-species oral biofilm formation and bacterial ecology.
abstract: Future therapies for the treatment of dental decay have to consider the importance of preserving bacterial ecology while reducing biofilm adherence to teeth. A multi-species plaque-derived (MSPD) biofilm model was used to assess how concentrations of N-acetyl-l-cysteine (NAC) (0, 0·1, 1, 10%) affected the growth of complex oral biofilms. Biofilms were grown (n = 96) for 24 h on hydroxyapatite discs in BMM media with 0·5% sucrose. Bacterial viability and biomass formation was examined on each disc using a microtitre plate reader. In addition, fluorescence microscopy and Scanning Electron Microscopy was used to qualitatively examine the effect of NAC on bacterial biofilm aggregation, extracellular components and bacterial morphology. The total biomass was significantly decreased after exposure of both 1% (from 0·48, with a 95% confidence interval of (0·44, 0·57) to 0·35, with confidence interval (0·31, 0·38)) and 10% NAC (0·14 with confidence interval (0·11, 0·17)). 16S rRNA amplicon sequencing analysis indicated that 1% NAC reduced biofilm adherence while preserving biofilm ecology.
  
  
  CONCLUSIONS
  As a compound with a wide safety margin, N-acetyl-l-cysteine (NAC) has the potential to be used as a long term anti-plaque bacteriostatic agent for managing chronic dental decay without substantially altering biofilm's bacterial ecology. The potential anti-caries benefit of NAC is directly related to reducing the biofilm coverage which reduces the degree of acid generation and the amount of time that the surface is exposed to a lower pH.
authors.affiliation: Division of Pediatric Dentistry, Department of Developmental and Surgical Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: K
authors.initials: K
authors.lastname: Rasmussen
authors.affiliation: Division of Pediatric Dentistry, Department of Developmental and Surgical Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: J
authors.initials: J
authors.lastname: Nikrad
authors.affiliation: Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, USA.
authors.forename: C
authors.initials: C
authors.lastname: Reilly
authors.affiliation: Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota School of Dentistry, Minneapolis, MN, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.affiliation: Division of Pediatric Dentistry, Department of Developmental and Surgical Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Jones
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D003731:Dental Caries / Q000382:microbiology / Q000517:prevention & control*; D003773:Dental Plaque / Q000382:microbiology / Q000517:prevention & control*; D050296:Microbial Viability / Q000187:drug effects; D012336:RNA, Ribosomal, 16S
chemical_list: D000900:Anti-Bacterial Agents; D012336:RNA, Ribosomal, 16S; D000111:Acetylcysteine
keywords: biofilms; caries; colonization; dental; disease; microbiome