title: Evolution of resistance to cationic biocides in Streptococcus mutans and Enterococcus faecalis.
abstract: OBJECTIVE
  The aim of this study was to investigate whether Streptococcus mutans and Enterococcus faecalis develop resistance to the cationic biocides chlorhexidine (CHX), cetylpyridinium chloride (CPC), and 12-methacryloyloxydodecylpyridinium bromide (MDPB).
  
  
  METHODS
  The minimum inhibitory concentrations (MICs) of CHX, CPC, and MDPB were assessed after repeated exposure of S. mutans and E. faecalis to these biocides. Cell-surface hydrophobicity and protein expression profiles of bacterial cells were examined to elucidate possible resistance mechanisms.
  
  
  RESULTS
  The MIC of CHX against E. faecalis showed constant increases up to 10 passages. No changes in the MICs of CPC and MDPB against E. faecalis were observed. The MICs of CHX, CPC, and MDPB against S. mutans did not increase. The surface hydrophobicity of E. faecalis significantly increased with increasing exposure to CHX and CPC. However, changes in protein expression profiles were only found in CHX-adapted E. faecalis, as evidenced by the emergence of a novel, approximately 19-kDa band following sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
  
  
  CONCLUSIONS
  While E. faecalis and S. mutans did not exhibit increased resistance to CPC or MDPB, repeated exposure of E. faecalis to CHX led to resistance. It is likely that the acquisition of resistance is related to an altered protein composition.
  
  
  CONCLUSIONS
  Alkyl pyridinium compounds, such as CPC and MDPB, could have a lower risk to cause adaptation of E. faecalis, which is advantageous compared with CHX.
authors.affiliation: Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan. Electronic address: h-kita@dent.osaka-u.ac.jp.
authors.forename: Haruaki
authors.initials: H
authors.lastname: Kitagawa
authors.affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Izutani
authors.affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Ranna
authors.initials: R
authors.lastname: Kitagawa
authors.affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Hazuki
authors.initials: H
authors.lastname: Maezono
authors.affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Mikiyo
authors.initials: M
authors.lastname: Yamaguchi
authors.affiliation: Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Imazato
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001422:Bacterial Adhesion / Q000187:drug effects; D002594:Cetylpyridinium / Q000494:pharmacology; D002710:Chlorhexidine / Q000494:pharmacology; D004202:Disinfectants / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008826:Microbial Sensitivity Tests; D011726:Pyridinium Compounds / Q000494:pharmacology; D013295:Streptococcus mutans / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D059467:Transcriptome / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D004202:Disinfectants; D011726:Pyridinium Compounds; C089392:methacryloyloxydodecylpyridinium bromide; D002594:Cetylpyridinium; D002710:Chlorhexidine
keywords: Cationic biocides; Drug resistance; Enterococcus faecalis