| Summary: | <i>Litsea cubeba</i> L. essential oil (LCEO) can affect the growth of drug-resistance bacteria. However, research on stress response of drug-resistant <i>A. baumannii</i> under sub-lethal LCEO concentrations had been limited so far. Therefore, transcriptomic analysis of <i>A. baumannii</i> under 1/2 minimum inhibitory concentration (MIC, 0.54 mg/mL) of LCEO was performed. Results of transcriptomic analysis showed that 320/352 genes were significantly up/down-regulated, respectively, in LCEO-treated <i>A. baumannii</i>. Both up and down-regulated genes were significantly enriched in three GO terms (oxidation-reduction process; oxidoreductase activity; oxidoreductase activity, acting on the CH-CH group of donors), which indicated that the redox state of <i>A. baumannii</i> was significantly affected by LCEO. LCEO may also inhibit aerobic respiration, synthesis of ketone bodies and the metabolism of some amino acids while, meanwhile, promoting fatty acid degradation of <i>A. baumannii</i> according to Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. The permeability and the stress of cell membrane of <i>A. baumannii</i> were significantly affected by LCEO. After crystal violet dyeing, the biofilm formation of <i>A. baumannii</i> was promoted/inhibited by extremely low/relatively high concentration of LCEO, respectively. LCEO and chloramphenicol have synergistic growth inhibitory effect against <i>A. baumannii</i> according to the Fractional Inhibitory Concentration Index (FICI) value = 0.375. Our results indicate that the growth of <i>A. baumannii</i> was inhibited by LCEO, and give insights into the stress response of <i>A. baumannii</i> under sub-lethal concentrations of LCEO. These results provided evidence that <i>A. baumannii</i> was inhibited by LCEO, and expanded knowledges of stress response of <i>A. baumannii</i> under sub-lethal concentration of LCEO.
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