title: Inhibiting effects of Enterococcus faecium non-biofilm strain on Streptococcus mutans biofilm formation.
abstract: OBJECTIVE
  Enterococcus faecium is a normal bowel commensal and lactic acid bacterium that is rarely found in the oral cavity. This study investigated whether a non-pathogenic and non-biofilm strain of E. faecium functioned as a probiotic strain toward biofilm formation by Streptococcus mutans, which is an etiological agent for dental caries.
  
  
  METHODS
  The effects of E. faecium on streptococcal biofilm was evaluated by absorbance of safranin-stained biofilm at 492 nm in a 96-well microtiter plate.
  
  
  RESULTS
  The E. faecium strain demonstrated cell-number-dependent inhibition of biofilm in dual cultures with 4 laboratory and 16 clinical S. mutans strains, as well as laboratory strains of Streptococcus sobrinus and Streptococcus sanguinis, in 96-well microtiter plates. The inhibiting effects of E. faecium were not dependent on the production of bacteriocin from streptococci and E. faecium, low pH after mix culture, or biofilm formation levels of S. mutans. A culture supernatant sample of more than 10 kDa from E. faecium showed direct inhibiting effects toward S. mutans biofilm formation. Treatment of heat, butanol, and phenol to a supernatant sample restored biofilm formation in culture of S. mutans with the sample. Moreover, the tendencies of inhibition levels by the supernatant sample were associated with those by bacterial cells of E. faecium to S. mutans strains.
  
  
  CONCLUSIONS
  The E. faecium non-biofilm strain produced an inhibiting protein to streptococci biofilm formation, showed various susceptibilities to inhibit streptococcal biofilm, and acted as a probiotic bacterial inhibitor of streptococcal biofilm formation.
authors.affiliation: Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kumada
authors.forename: Mizuho
authors.initials: M
authors.lastname: Motegi
authors.forename: Ryoma
authors.initials: R
authors.lastname: Nakao
authors.forename: Hideo
authors.initials: H
authors.lastname: Yonezawa
authors.forename: Hideki
authors.initials: H
authors.lastname: Yamamura
authors.forename: Junji
authors.initials: J
authors.lastname: Tagami
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Senpuku
mesh_terms: D001430:Bacteriocins / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D000440:Butanols; D002450:Cell Communication; D015169:Colony Count, Microbial; D016984:Enterococcus faecium / Q000502:physiology*; D006801:Humans; D019800:Phenol; D012463:Saliva / Q000382:microbiology; D018709:Statistics, Nonparametric; D013295:Streptococcus mutans / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D013696:Temperature
chemical_list: D001430:Bacteriocins; D000440:Butanols; D019800:Phenol