title: Streptococcus mutans biofilm disruption by κ-casein glycopeptide.
abstract: Caseinomacropeptide (CMP), the variably phosphorylated and glycosylated forms of the bovine milk protein fragment, κ-casein(106-169), is produced during cheese production and has been shown to have a range of antibacterial bioactivities.
  
  
  OBJECTIVE
  To characterise the biofilm disruptive component of CMP and compare its activity with the known antimicrobial agents chlorhexidine and zinc ions.
  
  
  METHODS
  Streptococcus mutans biofilms were grown in flow cells with an artificial saliva medium containing sucrose and treated with CMP and the glycosylated forms of κ-casein(106-169) (κ-casein glycopeptide, KCG). The biofilms were imaged using confocal laser scanning microscopy (CLSM) and quantified by COMSTAT software analysis. A static biofilm assay and flow cytometric analysis were used to examine the mechanism of action of chlorhexidine and a combination of KCG with the known antimicrobial agent ZnCl2 (KCG-Zn).
  
  
  RESULTS
  CLSM analysis showed that S. mutans produced robust, structured biofilms with an average thickness of 7.37μm and a biovolume of 3.88μm(3)/μm(2) substratum after 16h of incubation in the flow cell system. A single application of 10mg/mL CMP that contained 2.4mg/mL KCG significantly reduced total biofilm biovolume and average biofilm thickness by 53% and 61%, respectively. This was statistically the same as a 2.4mg/mL KCG treatment that reduced the total biovolume and average thickness by 59% and 69%, respectively, suggesting the KCG was the biofilm disruptive component of CMP. Chlorhexidine treatment (0.1%) caused similar effects in the flow cell model. KCG-Zn caused significantly more disruption of the biofilms than either KCG or ZnCl2 treatment alone. In a static biofilm model chlorhexidine was shown to work by disrupting bacterial membrane integrity whilst KCG-Zn had no effect on membrane integrity.
  
  
  CONCLUSIONS
  KCG and KCG-Zn may have potential as natural biofilm disruptive agents.
authors.affiliation: Oral Health Cooperative Research Centre, Melbourne Dental School and The Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Victoria, Australia.
authors.forename: Stuart G
authors.initials: SG
authors.lastname: Dashper
authors.forename: Sze-Wei
authors.initials: SW
authors.lastname: Liu
authors.forename: Katrina A
authors.initials: KA
authors.lastname: Walsh
authors.forename: Geoffrey G
authors.initials: GG
authors.lastname: Adams
authors.forename: David P
authors.initials: DP
authors.lastname: Stanton
authors.forename: Brent R
authors.initials: BR
authors.lastname: Ward
authors.forename: Peiyan
authors.initials: P
authors.lastname: Shen
authors.forename: Neil M
authors.initials: NM
authors.lastname: O'Brien-Simpson
authors.forename: Eric C
authors.initials: EC
authors.lastname: Reynolds
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001431:Bacteriological Techniques; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002364:Caseins / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology*; D002710:Chlorhexidine / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D003470:Culture Media; D015194:Diffusion Chambers, Culture; D005434:Flow Cytometry; D006801:Humans; D018613:Microscopy, Confocal; D010446:Peptide Fragments / Q000494:pharmacology*; D012464:Saliva, Artificial; D013295:Streptococcus mutans / Q000187:drug effects* / Q000502:physiology; D013395:Sucrose; D017967:Zinc Compounds / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D002364:Caseins; D002614:Chelating Agents; D002712:Chlorides; D003470:Culture Media; D010446:Peptide Fragments; D012464:Saliva, Artificial; D017967:Zinc Compounds; C065989:caseinomacropeptide; D013395:Sucrose; C016837:zinc chloride; D002710:Chlorhexidine