Mechanistic Insights Into the Effect of the Essential Oil of Ambrosia hispida Pursh. Against Multidrug-Resistant Clinical Isolates of Acinetobacter baumannii.

The emergence of antimicrobial-resistant bacteria has significantly compromised global public health. The World Health Organization has identified priority pathogens for research and new therapeutic strategies, highlighting carbapenem-resistant Acinetobacter baumannii as a critical priority. Ambrosia hispida essential oil (EO) from the Yucatan Peninsula was investigated for its anti-A. baumannii properties. GC-MS analysis identified 27 metabolites, predominantly sesquiterpenes and oxygenated sesquiterpenes, with spathulenol, caryophyllene oxide, and α-pinene as major compounds. This EO exhibited antibacterial activity against A. baumannii strains, strong inhibition of biofilm formation, and anti-quorum-sensing activity. Moreover, the EO also decreased bacterial survival in response to H₂O₂, indicating anti-catalase activity. Scanning electron microscopy (SEM) analysis confirmed the EO's ability to inhibit biofilm formation and cause morphological alterations in bacterial cells. Molecular docking studies revealed that kaurene, a diterpene in the EO, had the strongest interaction with bacterial targets involved in biofilm formation. The study highlights the potential of A. hispida EO as a promising candidate for developing agents to combat carbapenem-resistant A. baumannii.