title: The effect of MTADN on 10 Enterococcus faecalis isolates and biofilm: an in vitro study.
abstract: BACKGROUND
  Enterococcus faecalis is frequently isolated from both secondary and persistent root canal infections. MTAD is an effective intracanal irrigant, but its bactericidal activity requires improvement. The goal of this study was to investigate whether nisin, an antibacterial peptide, improves the antibacterial and antibiofilm activities of MTAD against E. faecalis clinical isolates.
  
  
  METHODS
  Ten E. faecalis strains were isolated from root canals with persistent periapical lesions. The antibacterial activity of MTAD, MTADN (nisin in combination with doxycycline), and MTAN (nisin in place of doxycycline) against E. faecalis isolates was evaluated using minimal inhibitory concentration and minimal bactericidal concentration assays. Scanning electron microscopy was used to observe E. faecalis biofilms on the chamber surface of the root canal, and confocal laser scanning microscopy was used to show the antibiofilm activity of the 3 irrigants.
  
  
  RESULTS
  Ten E. faecalis strains were successfully isolated from clinical samples by selective medium, colony morphology, oxygen tolerance, bile resistance, Gram staining characteristics, and polymerase chain reaction identification. The antimicrobials MTAD, MTADN, and MTAN had different antibacterial activities against the 10 E. faecalis isolates, with MTADN showing superior antibacterial efficacy compared with MTAD. Strain D had the greatest sensitivity to MTAD and MTADN, whereas strain E was the most resistant to these compounds. Strain E was able to form a mature biofilm with complex architecture. Importantly, confocal laser scanning microscopic images showed that MTADN was able to kill completely E. faecalis isolates grown as a biofilm, whereas MTAD was unable to do so.
  
  
  CONCLUSIONS
  MTADN effectively inhibited both the growth of E. faecalis root canal isolates and these isolates' biofilms. These results are encouraging and suggest that MTADN has a considerable potential for use as an effective irrigant.
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
authors.forename: Zhongchun
authors.initials: Z
authors.lastname: Tong
authors.forename: Junqi
authors.initials: J
authors.lastname: Ling
authors.forename: Zhengmei
authors.initials: Z
authors.lastname: Lin
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Li
authors.forename: Yunjing
authors.initials: Y
authors.lastname: Mu
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D058491:Bacterial Load / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002417:Cattle; D019343:Citric Acid / Q000008:administration & dosage / Q000494:pharmacology*; D003786:Dental Pulp Cavity / Q000382:microbiology; D004318:Doxycycline / Q000008:administration & dosage / Q000494:pharmacology*; D004338:Drug Combinations; D024881:Drug Resistance, Bacterial; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D009561:Nisin / Q000008:administration & dosage / Q000494:pharmacology*; D011136:Polysorbates / Q000008:administration & dosage / Q000494:pharmacology*; D012388:Root Canal Irrigants / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; C475043:MTAD (intracanal irrigant); D011136:Polysorbates; D012388:Root Canal Irrigants; D009561:Nisin; D019343:Citric Acid; D004318:Doxycycline