Antibacterial Effects of Origanum vulgare Essence Against Multidrug-Resistant Acinetobacter baumannii Isolated From Selected Hospitals of Tehran, Iran

Infection due to Acinetobacter baumannii has become a significant challenge to modern healthcare systems. The rapid emergence and global dissemination of A. baumannii as a major nosocomial pathogen is remarkable and it demonstrates its successful adaptation to the 21st century hospital environment. Recent studies have discussed about essential oil of Origanum vulgare against a range of bacteria, including various species of Staphylococcus, Pseudomonas, Bacillus and Escherichia coli. The present study aimed to investigate the inhibitory effects O. vulgare essence against multidrug-resistant (MDR) strains of A. baumannii from selected hospitals in Tehran, Iran. This oil was obtained using the hydrodistillation method and analyzed by gas chromatography mass spectrography (GC/MS). The antimicrobial activity against MDR isolates was achieved using disc diffusion method and macro-broth dilution assay. Analysis of the essential oil revealed the presence of pulegone (68.59%) piperitone (7.8%), piperitenone (7.8%), 1, 8-cineole (1.3%), and carvacrol (1.6%) as the major components. The results showed a significant activity against MDR A. baumannii with inhibition zones and minimal inhibitory concentration values in the ranges of 7-15 mm and 20-35 µL/mL respectively. This investigation showed that the essence oil of O. vulgare had a potent antimicrobial activity against MDR A. baumannii. Further research is required to evaluate the practical values of therapeutic applications.