Essential Oils and Their Multifunctional Activities Against Pseudomonas aeruginosa : Current Evidence and Perspectives

: Pseudomonas aeruginosa is an opportunistic pathogen responsible for acute and chronic infections and is characterized by a remarkable ability to develop antibiotic resistance. This has prompted increasing interest in alternative or complementary antimicrobial strategies, including the use of essential oils (EOs), which are complex mixtures of plant-derived volatile compounds with documented biological activities. This review aims to summarize and discuss the current evidence on the antimicrobial, antibiofilm, and anti-virulence activities of EOs against P. aeruginosa, with particular emphasis on their mechanisms of action, synergistic interactions with antibiotics, and limitation to the possible clinical applicability. A large number of studies, mainly conducted in vitro, indicate that EOs and their major constituents can impair P. aeruginosa viability and pathogenicity through multiple mechanisms. In addition, several EOs or purified terpene components exhibit synergistic effects when combined with conventional antibiotics, enhancing antimicrobial efficacy. However, in vivo evidence remains limited, largely restricted to topical infection models, while clinical studies in humans are currently lacking. Significant challenges related to chemical variability, toxicity, safety, standardization, and regulatory classification also emerge from the literature. Although EOs show considerable promise as antimicrobial and anti-virulence agents against P. aeruginosa, their current role should be viewed primarily as adjunctive or alternative strategies rather than as standalone systemic therapies. Future progress will depend on the development of standardized and safer formulations, advanced delivery systems, and well-designed in vivo and clinical studies.