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Introduction: Plant products are sources for drug development against multidrug resistant bacteria., Methods: The antimicrobial activity of Origanum vulgare L. essential oil (OVeo) against carbapenem-resistant strains was assessed by disk-diffusion, microdilution (REMA-Resazurin Microtiter Assay), and time kill assays., Results: Carbapenemase production was confirmed for all strains. OVeo exhibited a minimum inhibitory concentration of 0.059% v/v for Klebsiella pneumoniae and Serratia marcescens, and of 0.015 % v/v for Acinetobacter baumannii. A decrease in cell count was observed after a 4 h treatment., Conclusions: OVeo antimicrobial effect was rapid and consistent, making it a candidate for developing alternative therapeutic options against carbapenem-resistant strains.

The global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) strains has restricted the therapeutic options available to treat infections due to this pathogen. Understanding the prevalence of such infections and the underlying genetic mechanisms of resistance may help in the implementation of adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting. This study describes the molecular characteristics and risk factors associated with OXA-23-producing A. baumannii infections. A case-control study was undertaken from September/2013 to April/2015. Acquisition of OXA-23-producing A. baumannii was found to be associated with the use of nasogastric tubes, haemodialysis, and the use of cephalosporins. These isolates were only susceptible to amikacin, gentamicin, tigecycline, and colistin, and contained the ISAba1 insertion sequence upstream ofblaOXA-23 and blaOXA-51 genes. Twenty-six OXA-23-producing A. baumannii strains belonged to the ST79 (CC79) clonal group,and patients infected or colonised by these isolates had a higher mortality rate (34.6%). In conclusion, this study showed a dissemination of OXA-23-producing A. baumannii strains that was associated with several healthcare-related risk factors and high mortality rates among intensive care unit patients., Competing Interests: A.C.G. has recently received research funding and/or consultation fees from Bayer, MSD, and Pfizer. This does not alter our adherence to PLOS ONE policies on sharing data and materials. The other authors have nothing to declare.

Multidrug-resistant Acinetobacter baumannii has emerged as a problematic hospital-acquired pathogen. It is vital to search for new sources of antibiotics. Natural plant essential oils have several biological properties, including antimicrobial activity and may be valuable for new drug development. Chemical composition of the essential oil of Nectandra megapotamica flowers was assessed by Gas Chromatography/Flame Ionization Detector and Gas Chromatography/Mass Spectrometry analysis. Antibacterial activity against OXA-23-producing A. baumannii and synergism with antibiotics were performed by broth microdilution, time kill, and checkerboard methods. The essential oil of Nectandra megapotamica flowers showed a predominance of oxygenated sesquiterpenes and caryophyllene oxide was the main component. Survival curves showed a linear decrease in viable OXA-23-producing A. baumannii cell counts over time for the association between the essential oil of Nectandra megapotamica flowers and imipenem. Checkerboard assay with imipenem presented Fractional Inhibitory Concentration Index of 0.156, suggesting synergism. The synergistic effect of essential oil of Nectandra megapotamica flowers with imipenem could be a potential approach to combat multiresistant OXA-23-producing A. baumannii strains, and could be used as a drug delivery system, as an excipient for imipenem, reducing its dosage. [ABSTRACT FROM AUTHOR]