Study On Antimicrobial Effect And Mechanism Of Portulaca Oleracea L. Against Extended-Spectrum-β-Lactamase-Producing Escherichia Coli

Aiming at the high increasing rate of antibiotic resistance of bacteria from animals, The study was designed to observe the bacteriostatic action and bacteriostatic mechanism of Portulaca oleracea L. extracts against Drug-resistant E.coli. All above studies could supply for the treatment of colibacillosis in livestock and poultry and screening of new bacteriostatic agent from traditional Chinese medicine.The article used disk diffusion method to detect whether isolated E.coli strains producing ESBLs, and detected the ESBLs genotype by polymerase chain reaction, and tested the antibiotic sensitivity of 12 kinds of antimicrobial agents to the E.coli isolates by broth microdilution method. The results showed that isolates contain TEM and CTX-M genotype. And the isolated strain appeared diversely high resistance to 12 kinds of antimicrobial agents, especially for ceftriaxone, ceftofur, cefotaxime, amikacin, florfenicol and clindamycin, followed by quinolones.In addition, the bacteriostatic effect of 12 water extracts of Chinese traditional medicines was detected. Portulaca oleracea L showed the best antibacterial effect to extended-spectrum (3-lactamase (ESBLs) and non-ESBLs producing Escherichia coli. The minimal inhibitory concentration respectively was 125 mg/mL、62.5 mg/mL. So Portulaca oleracea L was chosen for further study.The drug susceptibility testing of different polarity solvents extracts from Portulaca oleracea L showed the ethanol extract had the best antibacterial effect, MIC was 62.5 mg/mL. Followed by aqueous extract, MIC was 125mg/mL. Antibacterial effect of different polarity solvents extracts from Portulaca oleracea L combined with 12 kinds of antimicrobial agents on extended spectrum β-lactamases-producing Escherichia coli was then investigated respectively. The results showed the 6 kinds of Portulaca oleracea L extracts have varying degrees of antibacterial effect. The effect of ethyl acetate extract and aqueous extract was the best, and the next was ethanol extract.The article investigated the antimicrobial mechanism of ethanol extract and aqueous extract to ESBLs-producing E.coli. Studies on the growth curves of E.coli showed that ethanol extract and aqueous extract inhibited the logarithmic split period of E.coli, and in a concentration-dependent manner. The observations with transmission election microscope showed that ethanol extract and aqueous extract caused the cell wall became thinning obviously, cytoplasm was concentrated and produced a cavity, cell membrane was separated from cell wall. Observation of the content of AKP and soluble protein revealed that ethanol extract and aqueous extract could influence the structure of the cell wall and membrane, and led to the increment of cell permeability. The observation of SDS-polyacrylamide gel electrophoresis showed that ethanol extract and aqueous extract can inhibit the synthesis of proteins.