title: In vitro combinations of antibiotics and phytochemicals against Pseudomonas aeruginosa.
abstract: OBJECTIVE
  Antibiotic combinations are used to enhance antibacterial efficacy and to prevent the development of resistance. In this study, the in vitro activities of antibiotic and phytochemical combinations against Pseudomonas aeruginosa were tested by the fractional inhibitory concentration method, derived from the minimal inhibitory concentrations (MICs) of the agents in combination.
  
  
  METHODS
  The antimicrobial activity of phytochemicals, alone and in combination with antibiotics, was evaluated using the checkerboard assay and time-kill curve methods.
  
  
  RESULTS
  There was synergism between gentamicin and caffeic acid, and sulfadiazine and the 3 phytochemicals under investigation (protocatechuic acid, quercetin, caffeic acid). The MIC of sulfadiazine was 256 microg/mL, and of gentamicin was 2 microg/mL. When gentamicin was combined with one-quarter the MIC of caffeic acid, the MIC of gentamicin was reduced 4-fold. When sulfadiazine was tested with one-quarter the MIC of protocatechuic acid, quercetin, and caffeic acid, the MIC was reduced 4-fold in combination with each of the drugs.
  
  
  CONCLUSIONS
  These results indicate the potential efficacy of phytochemicals in combination with antibiotics for enhancing total biological activity.
authors.affiliation: Biomedical Engineering Research Centre, Nanyang Technological University, Singapore. mmeena@ntu.edu.sg
authors.forename: Meena K
authors.initials: MK
authors.lastname: Sakharkar
authors.forename: Premkumar
authors.initials: P
authors.lastname: Jayaraman
authors.forename: Win Mar
authors.initials: WM
authors.lastname: Soe
authors.forename: Vincent T K
authors.initials: VT
authors.lastname: Chow
authors.forename: Lim Chu
authors.initials: LC
authors.lastname: Sing
authors.forename: Kishore R
authors.initials: KR
authors.lastname: Sakharkar
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002109:Caffeic Acids / Q000494:pharmacology*; D004347:Drug Interactions; D062385:Hydroxybenzoates / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D011794:Quercetin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D002109:Caffeic Acids; D062385:Hydroxybenzoates; D010936:Plant Extracts; C009091:protocatechuic acid; D011794:Quercetin; C040048:caffeic acid