Origanum vulgare essential oil: antibacterial activities and synergistic effect with polymyxin B against multidrug-resis
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ORIGINAL ARTICLE
Origanum vulgare essential oil: antibacterial activities and synergistic effect with polymyxin B against multidrug‑resistant Acinetobacter baumannii Suélen Cavalheiro Amaral1 · Beatriz Bohns Pruski2 · Stella Buchhorn de Freitas1 · Suzane Olachea Allend2 · Marcos Roberto Alves Ferreira1 · Clóvis Moreira Jr.1 · Daniela Isabel Brayer Pereira2 · Antonio Sergio Varela Junior3 · Daiane Drawanz Hartwig1,2,4 Received: 7 July 2020 / Accepted: 6 November 2020 © Springer Nature B.V. 2020
Abstract Antimicrobial resistance is increasing around the world and the search for effective treatment options, such as new antibiotics and combination therapy is urgently needed. The present study evaluates oregano essential oil (OEO) antibacterial activities against reference and multidrug-resistant clinical isolates of Acinetobacter baumannii (Ab-MDR). Additionally, the combination of the OEO and polymyxin B was evaluated against Ab-MDR. Ten clinical isolates were characterized at the species level through multiplex polymerase chain reaction (PCR) for the gyrB and blaOXA-51-like genes. The isolates were resistant to at least four different classes of antimicrobial agents, namely, aminoglycosides, cephems, carbapenems, and fluoroquinolones. All isolates were metallo-β-lactamase (MβL) and carbapenemase producers. The major component of OEO was found to be carvacrol (71.0%) followed by β-caryophyllene (4.0%), γ-terpinene (4.5%), p-cymene (3,5%), and thymol (3.0%). OEO showed antibacterial effect against all Ab-MDR tested, with minimum inhibitory concentrations (MIC) ranging from 1.75 to 3.50 mg mL−1. Flow cytometry demonstrated that the OEO causes destabilization and rupture of the bacterial cell membrane resulting in apoptosis of A. baumannii cells (p 0.5 and ≤ 1.0, additive interaction effect; > 1 and 640 nm) photomultipliers filters, respectively, and also blue laser (488 nm). All assays were performed in triplicates. Reactive oxygen species (ROS) The 2′-7′-dichlorofluorescein diacetate (DCFH-DA) assay was used to measure the ROS in cells. Since the dye diffuses into the cell, it is deacetylated by intracellular esterases into a non-fluorescent compound (chloromethyl-H2DCFDA), which is then oxidized by cellular ROS to a green fluorescent compound (DCFH-DA). After 24 h exposure to OEO, DCFH-DA (2 μL of the probe to each 50 μL of the final solution) and 2 μL of PI was added and incubated at room temperature for 30 min. Of the H33342 cell marker, 1 μL was then added and after further incubation for 15 min, 4% formalin was added in a 1:1 ratio. The cells were washed 2–3 times with phosphate-buffered saline (PBS) to remove formalin and following eluted in 300 µl of PBS.
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Molecular Biology Reports
Lipid peroxidation (LPO) LPO was determined using a lipid fluorescent probe (C 581/591 :4,4-difluoro-5-(4-phenyl-1,3-butadieny 11BODIPY l)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid). LPO occurs in the presence of ROS, wherein free radical-induced oxidation leads to a change in the color of t
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