The Screen Of Active Compounds Against Staphylococcus Aureus And Pseudomonas Aeruginosa

The most frequent multi-drug resistant(MDR)bacteria:Enterococcus faecalis,Staphylococcus aureus,Klebsiella pneumoniae,Acinetobacter baumannii,Pseudomonas aeruginosa and Enterobacter spp are the common reason for nosocomial infection.And WHO called them "ESKAPE" following their first initial.The minimal inhibitory concentration of 3053 compounds against "ESKAPE" was tested,and 2 of them(F2724-0690 and F2655-0471)show significant inhibitory activity against methicillin-resistant staphylococcus aureus(MRSA)but no activity against wild type strains.The F2724-0690-resistant S.aureus JE2 was obtained by serial passage of bacteria in the presence of sub-MIC levels.The drug-resistant spectrum of drug-resistant and drug-sensitive JE2 was analyzed.The data suggested that the target of F2724-0690 may be associated with the synthesis of cell wall.Many researches support the view that one reason of methicillin resistant of S.aureus is that the penicillin-binding protein 2(PBP2),the target of methicillin,is replaced by PBP2a which shows low affinity with methicillin.According to this,the target of F2724-0690 may be PBP2a.And the Docking Simulation study showed that F2724-0690 can interact with PBP2a,but we need more data to support our hypothesis.P.aeruginosa is one of the main pathogens caused nosocomial infection.The most important reason for natural resistance of P.aeruginosa is the outer membrane covering the cell.From the respect of biofilm,P.aeruginosa isolates can stick on the surface of medical apparatus and instruments which increase the frequency of infection,and are protected because of the decrease of antibiotics permeability.Polymyxin B,can increase the permeability of membrane by inserting into the biofilm.The bacteria are killed by polymyxin B because of the spillover of cell contents.And most of the resistant Gram-negative "superbugs" are still susceptible to polymyxin B.But the usage of polymyxin B is shadowed by the nephrotoxicity.We screened 1000 compounds through high-throughput synergy screen platform in our lab to get compounds which show synergistic effect with polymyxin B.Two compounds(11400-59 and shj-916)show synergistic effect with polymyxin B against P.aeruginosa.The P.aeruginosa-infected C.elegans animal model was established in our lab to investigate the activity in vivo.One of the two drug-combinations,11400-59 plus polymyxin B,was evaluated on this model.The synergistic effect of the combination of 11400-59 plus polymyxin B was verified on the unique whole animal model.In summary,one compound shows significant inhibitory activity against MRSA but shows no activity against wild type stain and a target hypothesis is given.Two compounds show synergistic effect with polymyxin B against P.aeruginosa,and the synergistic effect was verified on animal model.The case in this paper give anther support evidence of combination therapy and the animal verification may promote the development of combination therapy to clinical application.