title: Use of carvacrol, thymol, and eugenol for biofilm eradication and resistance modifying susceptibility of Salmonella enterica serovar Typhimurium strains to nalidixic acid.
abstract: The Aims of the study was to evaluate the antibacterial susceptibility and the biofilm eradication of three natural compounds carvacrol (CAR), thymol (TH) and eugenol (EUG), alone or in combination with nalidixic acid (NA) against twelve Salmonella Typhimurium strains. The minimum inhibitory concentration (MIC) and the minimum biofilm eradication concentration (BEC50) of the tested compounds (CAR, TH and EUG) and their combinations with NA were evaluated. In order to assess whether these bacteria had active efflux pumps, ethidium bromide (EtBr) accumulation assays was achieved using spectrophotometric accumulation assays. Moreover, scanning electron microscopy was used to visualize the bacterial biofilm formation on stainless steel surfaces after exposed to NA, CAR, TH and EUG alone and in combination. TH was the most effective essential oil, with the lowest MICs values ranging from 32 to 128 μg/mL followed by EUG and CAR. In addition, the combination of NA with the different compounds enhances antibiotic susceptibility of the tested bacterial strains. These results were confirmed by EtBr accumulation assays. A pronounced effect in decreasing biofilm mass was also noticed. Moreover, SEM revealed that bacterial membrane was disrupted and a complete loss of membrane integrity was also evident. The combination of natural compounds with antibiotic enhances bacterial susceptibility to NA. This combination ameliorates eradication of biofilm formed by S. Typhimurium on polystyrene microtitre plates. Additionally, this synergy induces an alteration of the bacterial cell surface visualized by SEM.
authors.affiliation: Laboratory of Analysis, Treatment and Valorization of Pollutants of the Environment and Products, Faculty of Pharmacy, Rue Avicenne, Monastir University, Tunisia.
authors.forename: Hanene
authors.initials: H
authors.lastname: Miladi
authors.affiliation: Laboratory of Analysis, Treatment and Valorization of Pollutants of the Environment and Products, Faculty of Pharmacy, Rue Avicenne, Monastir University, Tunisia.
authors.forename: Tarek
authors.initials: T
authors.lastname: Zmantar
authors.affiliation: College of Applied Medical Sciences, Medical Laboratory Department, Yanbu el Bahr, Taibah University, Al Madinah Al Monawarah, Saudi Arabia. Electronic address: bochrak@yahoo.fr.
authors.forename: Bochra
authors.initials: B
authors.lastname: Kouidhi
authors.affiliation: Laboratory of Bacteriology and Molecular Biology, Hôspital of Ibn El Jazzar, Kairouan, Tunisia.
authors.forename: Yassine
authors.initials: Y
authors.lastname: Chaabouni
authors.affiliation: Laboratory of Analysis, Treatment and Valorization of Pollutants of the Environment and Products, Faculty of Pharmacy, Rue Avicenne, Monastir University, Tunisia; Laboratory of Bacteriology and Molecular Biology, Hôspital of Ibn El Jazzar, Kairouan, Tunisia.
authors.forename: Kacem
authors.initials: K
authors.lastname: Mahdouani
authors.affiliation: Laboratory of Analysis, Treatment and Valorization of Pollutants of the Environment and Products, Faculty of Pharmacy, Rue Avicenne, Monastir University, Tunisia.
authors.forename: Amina
authors.initials: A
authors.lastname: Bakhrouf
authors.affiliation: College of Sciences, Biology Department, Yanbu el Bahr, Taibah University, Al Madinah Al Monawarah, Kingdom Saudi Arabia.
authors.forename: Kamel
authors.initials: K
authors.lastname: Chaieb
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D000081007:Cymenes; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial; D004357:Drug Synergism; D005054:Eugenol / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D039821:Monoterpenes / Q000494:pharmacology*; D009268:Nalidixic Acid / Q000494:pharmacology*; D009822:Oils, Volatile / Q000494:pharmacology; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000648:ultrastructure; D013943:Thymol / Q000494:pharmacology*
chemical_list: D000890:Anti-Infective Agents; D000081007:Cymenes; D039821:Monoterpenes; D009822:Oils, Volatile; D009268:Nalidixic Acid; D013943:Thymol; D005054:Eugenol; C073316:carvacrol
keywords: Antibacterial; Antibiofilm; Carvacrol; Efflux pumps inhibitors; Eugenol; Membrane disruption; Thymol