title: Trans-cinnamaldehyde from Cinnamomum zeylanicum bark essential oil reduces the clindamycin resistance of Clostridium difficile in vitro.
abstract: Therapy with antimicrobial drugs, such as clindamycin, that perturb the intestinal flora but fail to inhibit growth of other microorganisms can permit the proliferation of Clostridium difficile and the elaboration of exotoxin. Therefore, there has been increasing interest in the use of inhibitors of antibiotic resistance for use in combination therapy. The essential oil of Cinnamomum zeylanicum bark enhanced the bactericidal activity of clindamycin and decreased the minimum inhibitory concentration of clindamycin required for a toxicogenic strain of C. difficile. Thin-layer chromatography (TLC) analysis of the essential oil separated a fraction (R(f) = 0.54) that was the most effective at enhancing the clindamycin antimicrobial activity. Using gas liquid chromatography and known standards, the active fraction was identified as trans-cinnamaldehyde (3-phenyl-2-Propenal). Combinations of clindamycin and trans-cinnamaldehyde were tested to determine the fractional inhibitory concentration (FIC) index by conventional checkerboard titration. The FIC index for C. difficile was found to be 0.312, which confirmed the synergistic actions of clindamycin and trans-cinnamaldehyde. The presence of 20 microg/mL of trans-cinnamaldehyde decreased the MIC of clindamycin for C. difficile 16-fold, from 4.0 to 0.25 microg/mL. These results signify that low concentrations of trans-cinnamaldehyde elevate the antimicrobial action of clindamycin, suggesting a possible clinical benefit for utilizing these natural products for combination therapy against C. difficile.
authors.affiliation: Dept. of Pharmaceutical Biotechnology and Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Tehran Univ. of Medical Sciences, 14174 Tehran, Iran. shahverd@sina.tums.ac.ir
authors.forename: A R
authors.initials: AR
authors.lastname: Shahverdi
authors.forename: H R
authors.initials: HR
authors.lastname: Monsef-Esfahani
authors.forename: F
authors.initials: F
authors.lastname: Tavasoli
authors.forename: A
authors.initials: A
authors.lastname: Zaheri
authors.forename: R
authors.initials: R
authors.lastname: Mirjani
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives* / Q000032:analysis / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000032:analysis / Q000494:pharmacology*; D002855:Chromatography, Thin Layer; D002935:Cinnamomum zeylanicum / Q000737:chemistry*; D002981:Clindamycin / Q000494:pharmacology*; D016360:Clostridioides difficile / Q000187:drug effects* / Q000254:growth & development; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D004357:Drug Synergism; D008826:Microbial Sensitivity Tests; D009822:Oils, Volatile / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D009822:Oils, Volatile; D002981:Clindamycin; D000171:Acrolein; C012843:cinnamaldehyde