title: First study on antimicriobial activity and synergy between isothiocyanates and antibiotics against selected Gram-negative and Gram-positive pathogenic bacteria from clinical and animal source.
abstract: The emergence of new diseases and the resurgence of several infections that were controlled in the past, associated with recent increase of bacterial resistance have created the necessity for more studies towards to the development of new antimicrobials and new treatment strategies. The aim of the present study was to evaluate the in vitro synergy between different classes of important glucosinolates hydrolysis products-isothiocyanates with antibiotics (gentamycin and vancomycin), against important pathogenic bacteria: Escherichia coli, Enterococcus faecalis, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus. A disc diffusion method was used to evaluate the antibacterial activity. The antimicrobial activity of phytochemicals and combinations between gentamycin, vancomycin and phytochemicals were quantitatively assessed by measuring the inhibitory halos. The results showed a selective antimicrobial effect of isothiocyanates, and this effect was strictly related with their chemical structure. In general the benzylisothiocyanate was the most effective compound against both Gram-positive and Gram-negative bacteria. The Listeria monocytogenes and Staphylococcus aureus were the bacteria most affected either by the phytochemicals alone or by the combination phytochemical-antibiotic. The bacteria Pseudomonas aeruginosa was the less affected pathogen. The most important synergism detected occurred between the commercial antibiotics with benzylisothiocyanate and 2-phenylethylisothiocyanate. In conclusion, some isothiocyanates are effective inhibitors of in vitro bacterial growth, and they can act synergistically with antibiotics.
authors.affiliation: CECAV-Veterinary and Animal Science Research Center, Veterinary Science Department, University of Trás-os-Montes e Alto Douro, P.O. Box 1013, 5001-801 Vila Real, Portugal.
authors.forename: Carla
authors.initials: C
authors.lastname: Dias
authors.forename: Alfredo
authors.initials: A
authors.lastname: Aires
authors.forename: Richard N
authors.initials: RN
authors.lastname: Bennett
authors.forename: Eduardo A S
authors.initials: EA
authors.lastname: Rosa
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Saavedra
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000254:growth & development / Q000472:pathogenicity; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000254:growth & development / Q000472:pathogenicity; D017879:Isothiocyanates / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D013552:Swine / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D017879:Isothiocyanates