Origanum vulgare essential oil: antibacterial activities and synergistic effect with polymyxin B against multidrug-resistant Acinetobacter baumannii

• Published in: Molecular biology reports Vol. 47; no. 12; pp. 9615 - 9625
• Main Authors: Amaral, Suélen Cavalheiro, Pruski, Beatriz Bohns, de Freitas, Stella Buchhorn, Allend, Suzane Olachea, Ferreira, Marcos Roberto Alves, Moreira, Clóvis, Pereira, Daniela Isabel Brayer, Junior, Antonio Sergio Varela, Hartwig, Daiane Drawanz
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-12-2020; Springer Nature B.V
• Subjects: Acinetobacter baumannii; Acinetobacter baumannii - drug effects; Acinetobacter baumannii - enzymology; Acinetobacter baumannii - genetics; Acinetobacter baumannii - growth & development; Aminoglycosides - pharmacology; Animal Anatomy; Animal Biochemistry; Anti-Bacterial Agents - isolation & purification; Anti-Bacterial Agents - pharmacology; Antibacterial activity; Antibiotics; Antimicrobial agents; Antimicrobial resistance; Apoptosis; beta-Lactamases - genetics; beta-Lactamases - metabolism; Biomedical and Life Sciences; Carbapenemase; Carbapenems; Carbapenems - pharmacology; Carvacrol; Caryophyllene; Cell membranes; Cephalosporins - pharmacology; Cephems; Clinical isolates; Cymenes - isolation & purification; Cymenes - pharmacology; DNA Gyrase - genetics; DNA Gyrase - metabolism; Drug Combinations; Drug Resistance, Multiple, Bacterial - drug effects; Drug Resistance, Multiple, Bacterial - genetics; Drug Synergism; Essential oils; Flow cytometry; Fluoroquinolones; Fluoroquinolones - pharmacology; Gene Expression; Histology; Life Sciences; Metallo-β-lactamase; Microbial Sensitivity Tests; Minimum inhibitory concentration; Morphology; Multidrug resistance; Multidrug resistant organisms; Oils & fats; Oils, Volatile - chemistry; Oils, Volatile - pharmacology; Origanum - chemistry; Original Article; p-Cymene; Polycyclic Sesquiterpenes - isolation & purification; Polycyclic Sesquiterpenes - pharmacology; Polymerase chain reaction; Polymyxin B; Polymyxin B - pharmacology; Terpinene; Thymol; β Lactamase; Multidrug-resistant; Nosocomial infection; Oregano; Carvacrol; Phytotherapy; Synergism; Multidrug-resistant A. baumannii
• ISSN: 0301-4851; 1573-4978
• DOI: 10.1007/s11033-020-05989-0

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
bla
OXA-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
 < 0.05). Synergic interaction between OEO and polymyxin B (FICI: 0.18 to 0.37) was observed, using a checkerboard assay. When combined, OEO presented until 16-fold reduction of the polymyxin B MIC. The results presented here indicate that the OEO used alone or in combination with polymyxin B in the treatment of Ab-MDR infections is promising. To the best of our knowledge, this is the first report of OEO and polymyxin B association against Ab-MDR clinical isolates.