Analysis Of Antibiotic Resistance Genes And Phenotype Of Escherichia Coil From Pig And Chicken Intestines In Different Regions Of China

Antibiotic Resistance Genes（ARGs）,which is widely present in environmental media such as air,soil and water,has been defined globally as a novel environmental contaminant.The abuse of Antibiotics in the traditional industries of Livestock and poultry farming contributes to the high abundance and diversity of ARGs in intestinal bacteria of livestock and poultry,which has become an important source of ARGs accumulation pollution in the natural,and so that been a serious threat to the ecological environment and human health.Escherichia coli,as the dominant bacteria in the intestinal flora,is one of the main host bacteria of intestinal ARGs in livestock and poultry,and also the most commonly used gram-negative indicator bacteria,which means it can provide important information for contamination monitoring of livestock and poultry intestinal microbial ARGs.Many studies have reported the ARGs epidemic characteristics of Escherichia coli in livestock and poultry feces in some areas of China,but there are few reports on the abundance,diversity,and drug resistance phenotype of Escherichia coli in the intestinal tract of livestock and poultry in the whole country.In this article,Escherichia coli was isolated from five large-scale laying hen farms and five large-scale pig farms in Eastern China（Shandong,Jiangsu Province）,Southern China（Guangxi）,Western China（Sichuan Province）,Northern China（Hebei Province,Tianjin City）and Central China（Hubei Province）.Respectively,in order to obtain the overall pollution characteristics and background data of ARGs intestinal Escherichia coli in Livestock and poultry intestines from farms in different regions of China.The abundance and distribution characteristics of 21 representatives ARGs corresponding to 7 commonly used antibiotics in Escherichia coli were determined by real-time fluorescence quantitative PCR.The Minimum Inhibitory Concentration（MIC）of Escherichia coli to 7 common antibiotics was determined by microbroth dilution method.The main results are as follows:（1）The relative abundance of theβ-lactam antibiotic resistance gene bla Z and Durg and biocide resistance genes acr R and acr D were all higher in Escherichia coli isolated from pig and chicken intestinal tracts from farms in Eastern China（Shandong,Jiangsu Province）,Southern China（Guangxi）,Western China（Sichuan Province）,Northern China（Hebei Province,Tianjin City）and Central China（Hubei Province）.Their relative abundances ranged from 1.2757-2.7017（copies/16S r RNA）,0.0662-0.4423（copies/16S r RNA）and 0.0019-0.6234（copies/16S r RNA）in pig intestinal Escherichia coli,respectively,and from 0.6766-0.9290（copies/16S r RNA）,0.1244-0.1969（copies/16S r RNA）,1.11×10^-4-0.1491（copies/16S r RNA）in chicken intestinal Escherichia coli.（2）The relative abundance of the aminoglycoside resistance genes aac3,rmt B,rmt C,arm A and the quinolone resistance genes qnr D and mex A were low in both pig intestinal and chicken intestinal Escherichia coli in Eastern China（Shandong,Jiangsu Province）,Southern China（Guangxi）,Western China（Sichuan Province）,Northern China（Hebei Province,Tianjin City）and Central China（Hubei Province）,ranging from 10^-8 to10^-6（copies/16S r RNA）.（3）The total relative abundance of 21 ARGs of intestinal Escherichia coli isolated in Eastern China（Shandong,Jiangsu Province）,Southern China（Guangxi）,Western China（Sichuan Province）,Northern China（Hebei Province,Tianjin City）and Central China（Hubei Province）ranged from 2.15-2.86（copies/16S r RNA）for pigs,and0.77-1.18（copies/16S r RNA）for chickens.（4）The relative abundance of bla Z,theβ-lactam resistance gene of porcine enteric Escherichia coli,isolated from farms in Eastern China（Shandong,Jiangsu Province）,Southern China（Guangxi）,Western China（Sichuan Province）,Northern China（Hebei Province,Tianjin City）and Central China（Hubei Province）were all significantly higher than that of chicken enteric Escherichia coli（P<0.05）.Drug and biocide resistance genes acr D of porcine Escherichia coli isolated from farms in Eastern China（Shandong,Jiangsu Province）,Western China（Sichuan Province）and Northern China（Hebei Province,Tianjin City）were all significantly higher than those of chicken Escherichia coli（P<0.05）.In contrast,Durg and biocide resistance gene acr R was significantly higher（P<0.05）than chicken intestinal Escherichia coli only in farms in the eastern region of China（Shandong,Jiangsu Province）.（5）The resistance rates of 50 strains of pig intestinal Escherichia coli to Chloramphenicol,Tetracycline,Ampicillin,and Amoxicillin were 92%,90%,76%,and76%,Respectively.The MIC50 and MIC90 of Chloramphenicol and Tetracycline were 64μg/m L and 128μg/m L,the MIC50 and MIC90 of Ampicillin were as high as 512μg/m L,and the MIC50 and MIC90 of Amoxicillin were as high as 512μg/m L and 1024μg/m L.（6）The resistance rates of 50 strains of chicken intestinal Escherichia coli to Tetracycline,Ampicillin,and Amoxicillin were 88%,54%,and 54%.Respectively,the MIC50 and MIC90 for Tetracycline were 64μg/m L and 128μg/m L,and the MIC90 for Ampicillin and Amoxicillin was as high as 1024μg/m L.In summary,the total relative abundance of 21 representatives ARGs of pig intestinal Escherichia coli isolated from farm in Eastern China（Shandong,Jiangsu Province）,Southern China（Guangxi）,Western China（Sichuan Province）,Northern China（Hebei Province,Tianjin City）and Central China（Hubei Province）was generally higher than that of chickens intestinal Escherichia coli.The relative abundance of bla Z,acr R and acr D in both pig intestinal and chicken intestinal Escherichia coli were at a high level.While aac3,rmt B,rmt C,arm A and qnr D,mex A were at a low level.The resistance rates of pig intestinal and chicken intestinal Escherichia coli to Tetracycline,Ampicillin,and Amoxicillin were at high levels.This study provides background data for the ARGs pollution status and drug resistance phenotype of intestinal Escherichia coli from pigs and chickens.It provides a reference for reducing the ARGs pollution of livestock and poultry intestinal bacteria from the source and reducing the level of environmental drug resistance.