title: Effect of cinnamon oil on icaA expression and biofilm formation by Staphylococcus epidermidis.
abstract: Staphylococcus epidermidis is notorious for its biofilm formation on medical devices, and novel approaches to prevent and kill S. epidermidis biofilms are desired. In this study, the effect of cinnamon oil on planktonic and biofilm cultures of clinical S. epidermidis isolates was evaluated. Initially, susceptibility to cinnamon oil in planktonic cultures was compared to the commonly used antimicrobial agents chlorhexidine, triclosan, and gentamicin. The MIC of cinnamon oil, defined as the lowest concentration able to inhibit visible microbial growth, and the minimal bactericidal concentration, the lowest concentration required to kill 99.9% of the bacteria, were determined using the broth microdilution method and plating on agar. A checkerboard assay was used to evaluate the possible synergy between cinnamon oil and the other antimicrobial agents. The effect of cinnamon oil on biofilm growth was studied in 96-well plates and with confocal laser-scanning microscopy (CLSM). Biofilm susceptibility was determined using a metabolic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Real-time PCR analysis was performed to determine the effect of sub-MIC concentrations of cinnamon oil on expression of the biofilm-related gene, icaA. Cinnamon oil showed antimicrobial activity against both planktonic and biofilm cultures of clinical S. epidermidis strains. There was only a small difference between planktonic and biofilm MICs, ranging from 0.5 to 1% and 1 to 2%, respectively. CLSM images indicated that cinnamon oil is able to detach and kill existing biofilms. Thus, cinnamon oil is an effective antimicrobial agent to combat S. epidermidis biofilms.
authors.affiliation: Department of BioMedical Engineering, University Medical Center Groningen and University of Groningen, P.O. Box 196, 9700 AD Groningen, The Netherlands.
authors.forename: Titik
authors.initials: T
authors.lastname: Nuryastuti
authors.forename: Henny C
authors.initials: HC
authors.lastname: van der Mei
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: Susi
authors.initials: S
authors.lastname: Iravati
authors.forename: Abu T
authors.initials: AT
authors.lastname: Aman
authors.forename: Bastiaan P
authors.initials: BP
authors.lastname: Krom
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis; D018441:Biofilms / Q000187:drug effects*; D004357:Drug Synergism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D009822:Oils, Volatile / Q000494:pharmacology*; D013203:Staphylococcal Infections; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology*; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D009822:Oils, Volatile; D013778:Tetrazolium Salts; D013844:Thiazoles; C510049:cinnamon oil, leaf; C022616:thiazolyl blue