Prevalence Of Mcr-1 Resistance Genes In Escherichia Coli From Livestock And Poultry In Southwest Of Shandong Province

In 2016-2017,Colistin was detected several times before the export of chicken in southwest of Shandong Province,and it has attracted the attention of China's regulatory authorities and importing countries.According to investigations,Colistin is effective in preventing and controlling Gram-negative bacteria such as E.coli and Salmonella.It is often used in large quantities as a medical feed additives and preventive medicine.In recent years,reports of colistin resistance have appeared in many countries and regions around the world,and the mcr-1 has gradually become as a research hotspot at home and abroad.Therefore,the prevalence investigation of the colistin resistance gene mcr-1 in southwest of Shandong Province is not only the need for the export enterprises to improve the efficiency of using drugs,but also the need to eliminate the hidden danger of food safety supervision.This study combining the work of supervision,with the detection of colistin from the exported chicken in southwest of Shandong Province as a clue reviewed the biological characteristics of target bacteria of colistin,the status of bacterial resistance,common drug resistance mechanisms and resistance mediated by mcr-1 gene.In order to understand the prevalence of mcr-1 in southwest of Shandong Province,183 anal swabs were sampled from the chickens and pigs to be slaughtered from Jining,Zaozhuang,Linyi and Heze from April2018 to March 2019.After the collected samples were cultured in the enrichment and identification medium,they were subjected to Gram staining and biochemical identification,and the strains identified as E.coli were preserved with glycerol.Then,the identified E.coli were detected by polymerase chain reaction and agarose gel electrophoresis.The air,water,chicken manure and toilets of the mcr-1 positive farm were then sampled to isolate the E.coli which tested for mcr-1 to track the presence of mcr-1 in farm environment.The Antimicrobial susceptibility test was carried out between 40 mcr-1 positive and 40 mcr-1 negative E.coli by K-B diffusion method to analyse sensitive and resistant ratios for Polymyxin and other medicines.In this experiment,143 non-repetitive E.coli were obtained by isolation and identification.The detection results of the drug resistance gene mcr-1 indicated that a total of43 mcr-1 genes were detected,and the overall Carrier Rate of mcr-1 reached 25.9%.Amongthem,the Carrier Rate of chicken-derived E.coli was 33.7%,and the Carrier Rate of porcine-derived E.coli was 8.9%.13 strains of E.coli were isolated from two mcr-1 positive farms.Six mcr-1 resistance genes were detected from chicken manure,water and air in chicken house.Antimicrobial susceptibility test showed that 35% and 70% of mcr-1 positive and negative E.coli were susceptible to Polymyxin B respectively.Through experiments,we can understand the distribution and Carrier Rate of mcr-1derived from livestock and poultry in southwest of Shandong Province has a direct effect on exporting enterprises to improve drugs targeting and economic benefits.It also provides theoretical and data support for the authorities to develop colistin residue control measures and improve supervision levels.And the effectiveness of tracking and sampling the mcr-1positive farm environment was explored,which provided method reference and experience for the authorities and export enterprises to carry out environmental monitoring of the farm.