Nosocomial infections associated with carbapenem-resistant Acinetobacter baumannii are considered as a significant challenge in intensive care units' critical ill patients. The lack of new antimicrobial agents to treat infections caused by this multi-drug resistant microorganism reinforces the exploration of novel strategies to encounter and control this type of infection. Thus, the aim of the study was to evaluate, for the first time, the antibacterial effectiveness of Lavandula mairei Humbert

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... essential oil against carbapenem-resistant Acinetobacter baumannii isolated from the hospital environment of two intensive care units. Material and methods: Carbapenemase encoding genes were detected by PCR and sequencing methods. The chemical composition of Lavandula mairei essential oil was determined by gas chromatography-mass spectrometry analysis, and its antibacterial activity was evaluated by disk diffusion and broth microdilution methods. Results: OXA-23 and NDM-1 variants were revealed in the selected strains. Twenty-six compounds were identified in Lavandula mairei essential oil, in which carvacrol was the most dominant one (77.32%). All tested carbapenem-resistant Acinetobacter baumannii strains showed a wide sensitivity to the oil, with inhibition zones' diameters ranging from 28.67±1.15 mm to 40±2.00 mm, and a bactericidal effect proved by the similarity of minimal inhibitory and bactericidal concentrations values (0.39 to 3.125 µL/mL). Conclusion: These findings remain very promising for the future use of Lavandula mairei essential oil as a source of natural antibacterial agents.