Linalool exhibits potent antibacterial and anti-biofilm activity against carbapenem-resistant Acinetobacter baumannii

Acinetobacter baumannii poses an urgent clinical challenge due to its extensive antimicrobial resistance and enhanced capacity for biofilm development. These biofilm structures act as protective barriers that impede antibiotic penetration and shield bacterial cells from immune-mediated clearance, often leading to persistent and hard-to-treat infections. This investigation explored the therapeutic potential of linalool, a naturally occurring monoterpene alcohol, against clinical carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. Linalool demonstrated robust inhibitory effects on both early-stage biofilm formation and the disruption of preformed biofilms, as evidenced through crystal violet staining and live/dead viability imaging via confocal microscopy. Even at sub-inhibitory concentrations where planktonic growth was not fully suppressed, the growth kinetics changed in a dose-dependent manner. In addition, metabolic activity within the biofilms was markedly suppressed following linalool exposure, as determined by XTT reduction assays. At the molecular level, qPCR analysis revealed that linalool downregulated critical virulence- and resistance-associated determinants, including bap, bfmR, csuA/B, ompA, and bla_OXA-23. These cumulative findings indicate that linalool exerts a multi-targeted mechanism of action and may serve as a viable candidate for adjunctive therapies targeting CRAB in the context of rising antibiotic resistance.