Construction Of Unmarked Autoluminecent Acinetobacter Baumannii And Pharmacodynamic Study Of Ilamycin E

Acinetobacter baumannii(Ab)is a member of Gram-negative bacteria and is an important pathogen causing nosocomial infections.The public has been concerned about the bacteria due to the rising rates of drug-resistant Abs in recent years.This study first combined the Tn7 transposon with the dif sequences,successfully constructed an unmarked autoluminescent Ab(UAlAb)without any resistance marker by one step.The operon luxCDABE which can produce light without adding any extra substrates was contained in the genome of Ab and the light can be observed by naked eyes in darkness.Traditional site-specific recombination methods used for resistance marker excision required artificially expression of exogenous dissociation enzymes or transposases.Ab could produce Xer dissociation enzyme which can recognize dif sequences and then cut the resistance marker itself during proliferation without expression of exogenous protein.Thus,the Xer recombination system used for removing resistance marker is simple and convenient,avoiding a lot of unnecessary troubles.It has been reported used for the genetic manipulation of Mycobacterium in recent years,but no reports were found for its application to Ab so far.The results of this study indicated that the constructed UAlAb was similar to its parent strain(pt-Ab)in physical,and the inserted gene had no obvious influence on its growth,so its growth condition could be assessed by relative light units(RLUs).Furthermore,UAlAb could be used to substitute pt-Ab for in vitro compounds screening and evaluation,and its effect in vitro could be judged by RLUs,which can greatly reduce time,save materials and energy.As a result,it would be much faster to find drug candidates which show good effect against Ab.Tuberculosis(TB)is a chronic infectious disease caused by Mycobacterium tuberculosis(Mtb).Due to the emergence of drug-resistant TB,there is an urgent need of anti-TB drugs with new mechanisms.Ilamycin E(IL-E)is a cyclic heptapeptide compound derived from the Streptomyces atratus.It has been reported that had significant anti-TB activity which was better than that of the first-line drug rifampicin.The results of this study indicate that IL-E had good activity in vitro against Mtb.In addition,it had obvious effect at lower concentrations against clinical drug-resistant strains which were resistant to different drugs.Thus,IL-E may have new mechanisms of action and is worth further research.