title: Antibacterial effect of N-acetylcysteine and taurolidine on planktonic and biofilm forms of Enterococcus faecalis.
abstract: OBJECTIVE
  This study investigated the antimicrobial activity of taurolidine and N-acetylcysteine (NAC) on planktonic and biofilm Enterococcus faecalis phenotypes.
  
  
  METHODS
  The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of NAC and taurolidine were determined using broth microdilution, utilizing calcium hydroxide (CH), sodium hypochlorite, and chlorhexidine for comparisons. Thereafter, the ability of dentin powder to neutralize the antibacterial activity of NAC and taurolidine was studied. The efficacy of both antimicrobial agents on E. faecalis biofilms was examined quantitatively by exposure of 21-day-old E. faecalis biofilms on dentin disks. The cytotoxicity of human dental pulp fibroblast cells in contact with the extracts was evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay.
  
  
  RESULTS
  The MIC and MBC of NAC, taurolidine, and CH were not affected by pre-incubation in dentin powder. As verified by qualitative assay of E. faecalis biofilms, CH was the strongest bactericidal agent at all test dilutions, regardless of the presence of dentin powder. The antibacterial effect of NAC and taurolidine was significantly lower than that of CH at all test dilutions. At 48 h, all test agents showed similar, but high levels of cytotoxicity.
  
  
  CONCLUSIONS
  NAC and taurolidine were effective against E. faecalis in planktonic state, at the expense of demonstrating cytotoxic effects. For both planktonic and biofilm forms of E. faecalis, neither NAC nor taurolidine offered any advantage over CH.
authors.affiliation: Department of Pediatric Dentistry, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey.
authors.forename: Ayca Tuba
authors.initials: AT
authors.lastname: Ulusoy
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey.
authors.forename: Elif
authors.initials: E
authors.lastname: Kalyoncuoğlu
authors.affiliation: Department of Microbiology, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey.
authors.forename: Ahu
authors.initials: A
authors.lastname: Reis
authors.affiliation: Department of Pediatric Dentistry, Faculty of Dentistry, Hacettepe University, Ankara, Turkey.
authors.forename: Zafer C
authors.initials: ZC
authors.lastname: Cehreli
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D000900:Anti-Bacterial Agents; D018441:Biofilms; D003786:Dental Pulp Cavity / Q000382:microbiology; D003804:Dentin; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000254:growth & development; D006801:Humans; D013654:Taurine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013829:Thiadiazines / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D013829:Thiadiazines; D013654:Taurine; C012566:taurolidine; D000111:Acetylcysteine
keywords: Enterococcus faecalis; N-acetylcysteine; biofilm; dentin; taurolidine