Study On Dynamic Change Of Escherichia Coli With Resistance To Colistin From Swine In Different Growth Stages

Polymyxin in 1960 s are widely used in the treatment of gram negative bacterial infections,due to adverse reactions,polymyxin drugs narrow antimicrobial spectrum and has a more severe renal toxicity and neurotoxicity in 1980 s,antibiotics have been broader antibacterial spectrum,less adverse reactions such as beta lactam antibiotics substitute in clinic has been restricted but in recent years with the emergence of carbapenem resistant strains,polymyxin antibiotics for the treatment of multi drug resistant bacteria infection,and was re used in the clinical use of frequency is also increasing,and is considered the last choice for clinical anti infection.In 2015,Liu Jianhua first proposed the mechanism of colistin mcr-1 resistant Enterobacteriaceae plasmid mediated,related studies have confirmed that mcr-1 gene not only can be isolated from the animal body,from human and meat food can also be separated,and the separated strains resistant to colistin for Escherichia coli.Comparison and analysis of the local data carrying resistance to polymyxin E.coli for pigs in different regions of China at different growth stages in feces,clarify the colistin resistant gene diffusion and horizontal transmission mechanism,this study collected a total of 563 fecal samples from swine in Jilin Province,Jilin City,Changchun city in Meihekou Province,Gansu City of Zhangye Province,Gansu Province,Qingyang in the four regions,through the identification of colistin resistance selective medium,PCR for resistance to polymyxin E.coli;using the PCR method for screening of colistin resistance gene;method of using multiple PCR of colistin resistant Escherichia coli phylogenetic grouping,plasmid typing experiments;the minimum inhibitory concentration(MIC)experiment to determine the antimicrobial resistance of Escherichia coli was resistant to slime slime;by conjugation experiments to determine the drug resistance genes to spread,and the level of mechanism.Results show:From a total of 563 swine fecal samples were isolated and identified 273 strains of Escherichia coli in myxomycetes from Jilin City,Jilin province Changchun Meihekou city of Gansu Province,Zhangye City,Gansu Province,Qingyang City,four areas,the total isolation rate was 48.5%.In view of the 273 isolates detected colistin resistant gene mcr-1 and the detection rate was 100% mcr-1 resistance gene.Of the 273 strains were resistant to colistin in Escherichia coli isolated from the evolutionary clustering,the result shows that in the Qingyang City area three fattening stage,Changchun City,Meihekou city and Zhangye city in the breeding and fattening stage in A group was the dominant group,the second group B1.Four different regions in the stage of lactation phylogenetic grouping results are slightly different.Of 273 strains of colistin resistant Escherichia coli isolates plasmid replicon genotyping.Escherichia coli plasmid replicon common genotypes,the results showed that 11 kinds of plasmid were detected in different regions of the isolates were IncFIB type plasmid(41.8%,114/273),followed by type IncY plasmid(14.3%,39/273),IncFIC(8.8%,24/273)plasmid carrying mcr-1 gene can;plasmid replicon genotyping assay,the results showed that different regions of isolates were mainly X4 plasmid(38.1%,104/273),followed by type I2 plasmid(26.4%,72/273).The selection of four different regions in different growth stages of 172 strains isolates by conjugation experiment,the results showed that 123 strains conjugation,conjugation rate was 71.5%(123/172),and the zygote were carrying mcr-1 gene,mcr-1 gene in conjugative plasmid,and may be accompanied by a transfer plasmid and spread and diffusion.In four different regions selected in different growth stages of 172 strains isolated from samples and successful conjugation of 123 strains of zygote had minimal inhibitory concentration(MIC)experiments,the results showed that different isolates of colistin MIC value of 8?g/mL(83.7% 144/172),followed by 4?g/mL(14.5% 25/172),16?g/mL(1.8% 3/172).In the event of horizontal transfer after most of the transconjugants colistin MIC values consistent(86.2% 106/123),merozygote increase(7.3% 9/123)or lower(6.5% 8/123)changes.In this study,through the monitoring of different regions in different growth stages of pig resistance to colistin of Escherichia coli in data obtained from the initial grasp of the dynamic changes of pigs in different growth stages of colistin resistant Escherichia coli,provide reference data on resistance to polymyxin mcr-1 mechanism.