| Escherichia coli（E.coli）is the main pathogen of bacterial diarrhea in piglets,and its high pathogenicity and high level of multiple drug resistance increase the difficulty of prevention and treatment of piglet diarrhea,so it is urgent to research and develop safe and effective new drugs.Studies have shown that traditional Chinese medicine（TCM）has a good inhibitory effect on bacteria and has a certain elimination effect on bacterial resistance,which is of great significance for the prevention and control of drug-resistant bacteria.According to the principle of compatibility of TCM,this experiment selected heat-clearing and detoxifying herbs such as Flos Populi,Sanguisorbae Radix,Portulaca Oleracea L.and Humifuse Euphorbia Herb for compatibility with the clinically isolated and PCR-identified E.coli as the research object,the MIC and MBC of four groups of TCM compounds on E.coli were determined by microdilution method,and the effects of various TCM compounds on the microstructure of E.coli were observed under scanning electron microscope and transmission electron microscope,so as to clarify the inhibitory effect and mechanism of four groups of TCM compounds on E.coli in vitro;the drug resistance of E.coli was detected by K-B method,the drug resistance genes were amplified by PCR,and the drug resistance elimination rate of each TCM compound to multi-drug resistant E.coli was detected by photocopying method,and screened out the drug resistance elimination bacteria,and then the changes of E.coli resistant phenotypes and drug resistance genes were compared before and after the action of TCM to explore the mechanism of drug resistance elimination of E.coli by TCM compounds.Results are as follows:1.Flos Populi-Sanguisorbae Radi,Flos Populi-Portulaca Oleracea L.,Flos Populi-Humifuse Euphorbia Herb and Sanguisorbae Radix-Portulaca Oleracea L.could inhibit E.coli effectively,their MIC range was 62.5 mg/m L～250 mg/m L,and the MBC range was 125 mg/m L～500 mg/m L,the inhibitory effects of Flos Populi-Sanguisorbae Radix and Flos Populi-Humifuse Euphorbia Herb were better,with MIC of 62.5 mg/m L and MBC of 125 mg/m L.2.Scanning electron microscope and transmission electron microscope were used to observe the E.coli after the action of each TCM group.It was found that the bacterias were swollen,the surface was rough,and some of the cells were broken under the scanning electron microscope,and found that the bacterias were deformed,the internal vacuole was formed,the cell membrane structure of the cell wall were blurred,the cytoplasm was uneven,and some cells were ruptured under the transmission electron microscope.Among the four groups of TCM compounds,Flos Populi-Sanguisorbae Radix had the most obvious effect.3.37 strains of E.coli showed varying degrees of resistance to 15 antibiotics,with the most serious resistance to sulfamethoxazole and compound sulfamethoxazole the drug resistance rates were both 91.89%,followed by tetracycline（78.38%）and ampicillin（75.68%）;the detection rate of drug resistant gene bla TEMwas the highest（91.89%）,followed by aac C3-Ⅱ（37.84%）.4.The elimination rates of the four groups of TCM compounds to E.coli no.17 were all above 10%,the rate of Flos Populi-Portulaca Oleracea L.was the highest one（16%）;after the action of various Chinese medicines,E.coli became sensitive to gentamicin,and the three drug resistance genes aac C3-Ⅱ,aac C2 and aph（3’）-II were lost.The four groups of TCM compounds had no obvious elimination effect on the resistance of E.coli no.14.The above results showed that all the four groups of TCM compounds had certain inhibitory effects on E.coli,and the destruction of bacterial cell wall and cell membrane may be one of the main inhibitory mechanisms;each TCM compound could eliminate the resistance of E.coli to gentamicin,and led to the loss of three drug resistance genes:aac C3-II,aac C2,aph（3’）-II,the mechanism of drug resistance elimination was related to that E.coli resistance phenotypes were reversed by eliminating the major resistance genes. |
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