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-ß-lactamase (MßL) and carbapenemase producers. The major component of OEO was found to be carvacrol (71.0%) followed by ß-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.
Subject(s)
Acinetobacter baumannii/drug effects , Anti-Bacterial Agents/pharmacology , Drug Resistance, Multiple, Bacterial/drug effects , Oils, Volatile/pharmacology , Origanum/chemistry , Polymyxin B/pharmacology , Acinetobacter baumannii/enzymology , Acinetobacter baumannii/genetics , Acinetobacter baumannii/growth & development , Aminoglycosides/pharmacology , Anti-Bacterial Agents/isolation & purification , Carbapenems/pharmacology , Cephalosporins/pharmacology , Cymenes/isolation & purification , Cymenes/pharmacology , DNA Gyrase/genetics , DNA Gyrase/metabolism , Drug Combinations , Drug Resistance, Multiple, Bacterial/genetics , Drug Synergism , Fluoroquinolones/pharmacology , Gene Expression , Microbial Sensitivity Tests , Oils, Volatile/chemistry , Polycyclic Sesquiterpenes/isolation & purification , Polycyclic Sesquiterpenes/pharmacology , beta-Lactamases/genetics , beta-Lactamases/metabolismABSTRACT
In aquaculture, nutrition and supplemented diets have been shown to affect broodstock reproductive performance. In this study, we investigated the effects of dietary supplementation with Cymbopogon flexuosus essential oil (CFEO) microcapsules on reproductive-related parameters in silver catfish (Rhamdia quelen) male broodfish. Adult male broodstocks were separated into three groups according to the concentrations of supplemented CFEO (0.0 = control; 1.0 or 3.0 mL per kg of diet). After 20 days under experimental conditions, the animals were euthanized and the gonads were harvested for gonadosomatic index, sperm analysis, oxidative stress, and histopathology; testosterone levels were measured in the plasma; gene expression of prl, smtl, pomca, and pomcb was assessed in the pituitary gland by real-time PCR. The results showed no alterations on reproductive parameters in R. quelen males treated with Cymbopogon flexuosus essential oil compared to the control-diet animals. In conclusion, CFEO microcapsules supplied for 20 days in the concentrations of 1.00 or 3.00 mL per kilogram of diet did not affect the reproduction criteria evaluated in this study in male silver catfish.