Screening Of Quorum Sensing Inhibitors From Traditional Chinese Herbal Medicines On Multi-drug Resistant Pseudomonas Aeruginosa

The problems with drug-resistance are increasingly severe as multidrug-resistance bacteria pose a huge threat to human's health.Pseudomonas aeruginosa,an opportunistic and nosocomial pathogen,exhibits the impressive ability to acquire antibacterial resistance.The aim of this study is to screen the bioactive molecules from Chinese medicine,which directly interfere the bacterial biological activity rather than simply inhibit the bacterial growth.Furthermore,confirm the activity of the bioactive molecules through a series of biological experiments at gene and protein level.The thesis is devided into several parts,as follows:1.The P.aeruginosa strains isolated from clinic samples were tested for antimicrobial sensitivity by using the disk diffusion method.Alcoholic extracts of 1040 chinese herbal medicines,which were subjected to bacteriostatic tests in vitro.R-palsmid elimination experiment was performed in vitro by using the alcoholic extracts of Galla chinensis against P.aeruginosa with multi-drug resistance.2.A microarray-based screening platform was constructed onto a surface-activated polystyrence slide,which allowed functional characterization of herbal medicine extracts fractionated by HPLC.Using LasR as target quorum sensing protein,corresponding HPLC of 18 species out of 80 selected herbal medicine extracts that showed positive response to LasR.3.The active fractions of Galla chinensis were isolated by bioactivity-guided purification steps.Results of cell-based bioassay indicated that the fraction-Ye shown highest inhibitory activity toward LasR.The biological activity of the Ye fraction was further validated by quantitative reverse transcription PCR.The effects of Ye on the expression level of lasI,lasR,rhll,rhlR,pqsA and pasR were investigated.