[Antimicrobials discovery against Staphylococcus aureus by high throughput screening of drug library].

To develop antimicrobials against Staphylococcus aureus by high throughput screening of drug library. The type of this study is experimental research. The clinical isolates of S. aureus were collected from the sputum samples of respiratory inpatient department of the Third Xiangya Hospital of Central South University. The anti-planktonic cells growth inhibition activity of FDA-approved drugs library (including 1 573 molecules) was assessed by building a planktonic cells screening platform; The biofilm inhibitory effect of the FDA-approved drugs was detected by building a biofilm screening platform combined with crystal violet staining; Minimal inhibitory concentrations of the selected hits were determined by broth microdilution assay. Finally, the cytotoxicity of the selected hits was detected by CCK-8 assay. The results showed that 218 hits were exhibited effective growth inhibitory effects against S. aureus by setting the concentrations of the molecules in the FDA-approved library to 100 µmol/L. These selected molecules are mainly anti-infective drugs, accounting for 118 hits; Followed by anti-cancer drugs, anti-inflammatory/-immune drugs, neurological drugs, cardiovascular drugs, endocrine drugs, and metabolic disease drugs, which accounts for 40, 19, 12, 9, 8, and 3 hits; Other unclassified drugs accounts for 9 hits. The top 10 hits exhibiting anti-planktonic cells activity against S. aureus were mainly including antitumor drugs, followed by neurological drugs and unclassified drugs like vitamin K3 with the inhibition rate of 99.65%-100%. Similarly, the top 10 hits showing biofilm inhibitory effects against S. aureus were also mainly including antitumor drugs, followed by neurological drugs and anti-inflammatory/-immune drugs with the inhibition rate of 50.22%-92.95%. The minimal inhibitory concentration (MIC) of the 51 hits by second round screening was determined by micro-dilution assay, which mainly include the antitumor drugs, cardiovascular drugs, endocrine drugs, anti-inflammatory/-immune drugs, metabolic disease drugs, neurological drugs and other unclassified drugs accounted for 22, 5, 3, 9, 2, 5 and 5 hits, respectively, with the MICs of 1.56-50 µmol/L, 6.25-25 µmol/L, 6.25-25 µmol/L, 0.2-50 µmol/L, 25-50 µmol/L, 1.56-50 µmol/L and 0.1-12.5 µmol/L, respectively. In conclusion, the minimum inhibitory concentrations of small molecules screened through high-throughput assay are at the level of micromolar with strong drug development potential and high modifiability. The high effective anti-planktonic cells and anti-biofilm activity by these molecules are expected to provide new ideas for the development of new antimicrobials against S. aureus.

[Perifosine inhibits biofilm formation of Pseudomonas aeruginosa by interacting with PqsE protein].

To explore the biofilm inhibitory efficacy of perifosine against Pseudomonas aeruginosa (P. aeruginos) and its mechanisms. Twenty-fourwell plate was used to form biofilms at the bottom and crystal violet staining was used to determine the biofilm inhibitory effects of perifosine against P. aeruginosa, the wells without perifosine was set as control group. Glass tubes combined with crystal violet staining was used to detect the gas-liqud interface related bioiflm inhibitory effects of perifosine, the wells without perifosine was set as control group. Time-growth curved was used to detect the effects of perifosine on the bacteial planktonic cells growth of P. aeruginosa, the wells without perifosine was set as control group. The interaction model between perifosine and PqsE was assessed by molecular docking assay. The inhibitory effects of perifosine on the catalytic activity of PqsE was determined by detection the production of thiols, the wells without perifosine was set as control group. Binding affinity between perifosine and PqsE was detected by plasma surface resonance. The biofims at the bottom of the microplates and air-liquid interface were effectively inhibited by perifosine at the concentration of 4-8 µg/ml. There was no influence of perifosine on the cells growth of P. aeruginosa. The resuts of molecular docking assay indicates that perifosine could interacted with PqsE with the docking score of -10.67 kcal/mol. Perifosine could inhibit the catalytic activity of PqsE in a dose-dependent manner. The binding affinity between perifosine and PqsE was comfirmed by plasma surface resonance with KD of 6.65×10-5mol/L. Perifosine could inhibited the biofilm formation of P. aeruginosa by interacting with PqsE.