Study On The Mechanism Of Antibacterial Effect In Vitro Of Carbapenem-resistant Acinetobacter Baumannii By The Combination Of Baicalein And Meropenem

Objective: To explore the antibacterial effect and possible mechanism of baicalein and meropenem on carbapenem-resistant Acinetobacter baumannii(CRAB),and provide a new idea for clinical treatment of CRAB.Methods:(1)The sample submitted from January 2018 to September 2020 in the First People’s Hospital of Zunyi were collected for inoculation and culture.The automatic bacterial identification and drug sensitivity analysis system(Vitek2Compact60)was applied,the bacterial species identification and drug sensitivity test were carried out by the paper diffusion method(K-B method).The results were analyzed by WHONET5.6 software.(2)The minimum inhibitory concentration(MIC)of baicalein and meropenem against CRAB was determined by microbroth dilution method,and the time-growth curve of baicalein on CRAB was drawn.(3)The fractional inhibitory concentration index(FICI)of the combination of baicalein and meropenem was detected by checkerboard dilution method,and the combined effect of the drugs was evaluated according to the FICI value.(4)RT-PCR was used to detect the change in the transcription level of CRAB drug-resistant genes(adeA、adeR、adeS、OXA-23、OXA-51 、 CarO 、 OmpA)with sub-MIC meropenem,baicalein alone and in combination.Results:(1)A total of 422 CRAB strains were isolated and cultured in in the First People’s Hospital of Zunyi from January 2018 to September 2020,which was found to be the most the highest rate among carbapenem resistant strains,accounting for1.38‰.The specimens of isolated and cultured CRAB strains were mainly from sputum(77.73%),secretion and urine(4.27%),which accounted for 2.61%,2.13%,0.71% and 0.24% in sterile humoral blood,ascites,pleural fluid and cerebrospinal fluid,respectively.The isolated CRAB was mainly distributed in Neurointensive Care Unit(29.62%)and Intensive Care Unit(28.2%).The drug resistance rate of CRAB isolated and cultured in our hospital to common antibacterial agents were imipenem(99.29%),meropenem(98.82%),ceftazidime(98.82%),piperacillin and tazobactam(98.82%),ciprofloxacin(96.45%),piperacillin(96.92%),ampicillin and sulbactam(95 percent).35%),cefepime(90.28%),genamicin(89.81%),tobramycin(85.55%),amikacin(84.60%),cotrimoxazole(67.54%),levofloxacin(35.07%),minocycline(19.19%);(2)The MIC of baicalein alone for three CRAB studied was 50μg/ml and100μg/ml,and the time-growth curve show that baicalein had a certain antibacterial effect on CRAB;The MIC of meropenem alone for three CRAB studied was128μg/ml;The combination of baicalein and meropenem had an additive effect;(3)1/4 MIC concentration of baicalein activate the efflux pump genes adeA,adeR,adeS,β-lactamase genes OXA-23 and OXA-51,as well as the outer membrane porin genes CarO and OmpA;1/4 MIC concentration of baicalein combined with 1/4 MIC concentration of meropenem further activated the efflux pump gene adeJ and the outer membrane porin gene CarO in CRAB.Conclusion: CRAB isolated and cultured in our hospital was mostly derived from sputum specimens,which was mainly distributed in the Neurointensive Care Unit and Intensive Care Unit,with high resistance rate.Baicalein has a certain antibacterial effect on CRAB,and combined with meropenem can reduce the concentration of meropenem alone.Baicalin activated part of efflux pump,β-lactamase and outer membrane pore protein genes,combined with meropenem further activated adeJ and CarO genes.