Antibacterial Efficacy Of Litsea Cubeba L. Essential Oil Against Acinetobacter Baumannii In Vitro And Vivo

Acinetobacter baumannii is a common pathogen with complex drug resistance mechanism and strong survivability,developing new antibacterial drugs has come to be the focus of research which aims to prevent the infection epidemic caused by A.baumannii.In this study,the antibacterial and antibiofilm effect of Litsea cubeba L.essential oil against A.baumannii in vitro was evaluated,and explored the antibacterial mechanism through transcriptome analysis.Besides,the protection efficacy of LCEO against Abaumannii in vivo was verified by established the acute infection model of mice.The main results are as follows:1.The MIC and MBC of LCEO against A.baumannii was 1.04 mg/m L and 4.17 mg/m L,respectively.LCEO treatment significantly inhibited the growth of the bacteria,and the intracellular substances were leaked as the integrity of cell wall and membrane were destroyed by it.Furthermore,the content of nucleic acid and expression of protein in cell were reduced by LCEO,and it caused the cell morphology shrinkage and pili shedding of A.baumannii.2.The bacteria have a strong ability to form biofilms and mature biofilm was formed after the static culture for 48 h.The MBIC of LCEO against A.baumannii biofilm was 0.52 mg/m L,and it could not only inhibit the formation of biofilm but also possessed a significant scavenging effect on mature biofilms.The antibiofilm activity of LCEO may due to the decrease of extracellular polymer,the reducing of ability to aggregate and motility,and the decline of cell surface hydrophobicity.3.Compared to the control group,there were 672 differential expression genes were identified in the LCEO-tread group bacteria,320 genes were up regulated and 352 genes were down regulated.The differential genes were mainly enriched in pyruvate,fatty acid and various amino acid metabolism,oxidative phosphorylation,two-component system and peptidoglycan biosynthesis.After treatment with LCEO,the content of intracellular ATP and activity of ATPase were decreased with the content of ROS and MDA were increased,indicating that LCEO inhibited the energy metabolism of the bacteria and caused oxidative stress,which was consistent with the results of transcriptome sequencing.4.The survival rate of A.baumannii infected-mice was increased and the histological lesions were improved by the gavage of LCEO.Moreover,the number of white blood cell in blood and bacteria in organs were reduced,and the level of aminotransferase and cytokine were lowered of mice with the oral of LCEO,confirmed that the Inflammation and liver damage from bacterial infection were relieved by LCEO.In summary,LCEO exhibited the good antibacterial and antibiofilm effect in vitro,and mainly functioned by affecting bacterial structural integrity and energy metabolism.And LCEO also has an effective antibacterial activity in vivo as the systemic inflammatory response caused by bacteria infection was eased with the application of LCEO,thus,there was a certain preventive effect on the infection of Acinetobacter baumannii with LCEO.