Transcriptomics analysis reveals the molecular mechanisms of the antibacterial activity of gallium nitrate against Acinetobacter baumannii isolated from bloodstream infections. Transcriptomics analysis reveals the molecular mechanisms of the antibacterial activity of gallium nitrate against Acinetobacter baumannii isolated from bloodstream infections

Purpose: The aim of this study was to explore the antibacterial effect and molecular mechanism of gallium nitrate [Ga(NO 3 ) 3 ] against Acinetobacter baumannii from bloodstream infection. Methods: A total of 40 A. baumannii with different antimicrobials susceptibility patterns were isolated from bloodstream infections. In vitro antibacterial effect of Ga(NO 3 ) 3 was analyzed by micro-dilution method and time-kill assay. The effect of ferric chloride/heme on the antibacterial effect of Ga(NO 3 ) 3 was evaluated. Transcriptome sequencing was performed to elucidate the antibacterial mechanism of gallium nitrate. Mouse infection model was conducted to explore the in vivo efficacy of gallium nitrate . Results: Ga(NO 3 ) 3 exhibited excellent antibacterial effect in RPMI 1 640 medium containing 10% human serum (MICs ranged from 0.06 μg/mL to 0.125 μg/mL), whereas its antibacterial effect was weakened by exogenous ferric chloride/heme. Ga(NO 3 ) 3 inhibited A. baumannii growth in a dose- and time- dependent manner. Ga(NO 3 ) 3 exerted antibacterial effect by up-regulating the expression of genes associated with biosynthesis and transport of siderophore and disrupting multiple iron dependent metabolism processes. Ga(NO 3 ) 3 significantly reduced bacterial load in the neutropenic mouse thigh infection model. Conclusions: This study revealed that Ga(NO 3 ) 3 had excellent antibacterial activity both in vivo and in vitro . It might be a potential drug for treating bloodstream infections of A. baumannii Overall design: mRNA profiles of A. baumannii BM2333 wildtype and Ga(NO3 )3-treated BM2333