title: Interaction between lichen secondary metabolites and antibiotics against clinical isolates methicillin-resistant Staphylococcus aureus strains.
abstract: The in vitro antimicrobial activities of five compounds isolated from lichens, collected in several Southern regions of Chile (including the Chilean Antarctic Territory), were evaluated alone and in combination with five therapeutically available antibiotics, using checkerboard microdilution assay against methicillin-resistant clinical isolates strains of Staphylococcus aureus. MIC90, MIC50, as well as MBC90 and MBC50, for the lichen compounds were evaluated. The MIC90 was ranging from 32 µg/ml for perlatolic acid to 128 µg/ml for α-collatolic acid. MBC90 was ranging from onefold up to twofold the MIC90 for each compound. A synergistic action was observed in combination with gentamicin, whilst antagonism was observed for some lichen compounds in combination with levofloxacin. All combinations with erythromycin were indifferent, whilst variability was observed for clindamycin and oxacillin combinations. Data from checkerboard assay were analysed and interpreted using the fractional inhibitory concentration index and the response surface approach using the ΔE model. Discrepancies were found between both methods for some combinations. These could mainly be explained by the failure of FIC approach, being too much subjective and sensitive to experimental errors. These findings suggest, however, that the natural compounds from lichens are good candidates for the individuation of novel templates for the development of new antimicrobial agents or combinations of drugs for chemotherapy.
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Bellio
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Bernardetta
authors.initials: B
authors.lastname: Segatore
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Alisia
authors.initials: A
authors.lastname: Mancini
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Letizia
authors.initials: L
authors.lastname: Di Pietro
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Bottoni
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Sabatini
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Brisdelli
authors.affiliation: Department of Chemistry, Universidad Técnica F. Santa María, Casilla 110 V, Valparaíso, 6, Chile.
authors.forename: Marisa
authors.initials: M
authors.lastname: Piovano
authors.affiliation: Department of Enviromental Biology, University Sapienza, Rome, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Nicoletti
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Amicosante
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy.
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Perilli
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of l'Aquila, L'Aquila, Italy. Electronic address: celenza@univaq.it.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Celenza
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001565:Benzoates / Q000494:pharmacology; D002677:Chile; D004357:Drug Synergism; D008011:Lichens / Q000737:chemistry*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D064210:Secondary Metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001565:Benzoates; C522034:perlatolic acid
keywords: Antimicrobial activity; Checkerboard assay; Lichen secondary metabolites; MRSA