Abstract：Objective To study the inhibitory activity of gallium nitrate (GaN) on the bacterial growth and biofilm formation of carbapenem-resistant Klebsiella pneumoniae (CRKP). Methods The 82 clinical CRKP isolates were collected from the 34 hospitals of Anhui province from 2015 to 2016. The VITEK 2 Compact automated microbial analyzer was employed to conduct the bacterial identification. The minimal inhibitory concentrations (MIC) of 17 antibacterial drugs for these isolates were determined by the agar double dilution assay. The MIC of GaN was determined by the Micro-dilution method. The crystal violet staining assay was used to measure the A570 of CRKP in order to screen out strong biofilm-positive strains, and to test inhibitory effects of GaN (1/2MIC) on BF formation in 96-well plates. To compare the effects of Gallium nitrate with those of gentamicin on the biofilm formation of CRKP. The BF three-dimensional structure was visualized using the Confocal Laser Scanning Microscope. Results The clinical CRKP isolates demonstrated multidrug-resistance. In this study, the MIC of GaN for the 82 isolates was found to be in the range of 0.0625 to 2µmol/mL. The MIC50 was 0.25µmol/mL. The MIC90 was 0.5µmol/mL. The strong biofilm-positive strains accounted for 37.8% (31/82). Scanning electron microscopy imaging results revealed changes in amount of BF formation when the bacterial treated with GaN at different concentrations. The images demonstrated that GaN (1/2MIC) could significantly inhibit the biofilm formation of CRKP. The effects of gallium nitrate on the biofilm formation was superior to those of gentamicin. Conclusion GaN could significantly inhibit the growth and BF formation of CRKP.
