title: Antimicrobial efficacy of the alkaloid harmaline alone and in combination with chlorhexidine digluconate against clinical isolates of Staphylococcus aureus grown in planktonic and biofilm cultures.
abstract: OBJECTIVE
  To investigate the antimicrobial efficacy of an alkaloid, harmaline alone and in combination with chlorhexidine digluconate (CHG) against clinical isolates of Staphylococcus aureus (S. aureus) grown in planktonic and biofilm cultures.
  
  
  METHODS
  Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined for each micro-organism grown in suspension and in biofilm using microbroth dilution method. Chequerboard assays were used to determine synergistic, indifferent or antagonistic interactions between harmaline and CHG, and the some of results were verified by confocal laser scanning microscopy.
  
  
  RESULTS
  Harmaline and CHG showed effective antimicrobial activity against suspensions and biofilm cultures of S. aureus, respectively. As determined by fractional inhibitory concentration index (FICI), synergistic antimicrobial effects between harmaline and CHG were observed in nine and 11 of the 13 S. aureus strains when in suspension and in biofilm, respectively. FICI values were from 0·375 to 1·25 when in suspension and from 0·25 to 1·25 when in biofilm.
  
  
  CONCLUSIONS
  Synergistic activity of harmaline and CHG against clinical isolates of S. aureus (in suspension and in biofilm) was observed in vitro.
  
  
  CONCLUSIONS
  This study might provide alternative methods to overcome the problem of drug-resistance of S. aureus both in suspension and in biofilm.
authors.affiliation: Key Laboratory for Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun, China.
authors.forename: M
authors.initials: M
authors.lastname: Xing
authors.forename: F
authors.initials: F
authors.lastname: Shen
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: N
authors.initials: N
authors.lastname: Guo
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: W
authors.initials: W
authors.lastname: Wang
authors.forename: K
authors.initials: K
authors.lastname: Zhang
authors.forename: X
authors.initials: X
authors.lastname: Wu
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: S
authors.initials: S
authors.lastname: Sun
authors.forename: L
authors.initials: L
authors.lastname: Yu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D002710:Chlorhexidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004338:Drug Combinations; D004357:Drug Synergism; D006246:Harmaline / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010933:Plankton / Q000187:drug effects; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D006246:Harmaline; C010882:chlorhexidine gluconate; D002710:Chlorhexidine