| Livestock and poultry breeding occupies an indispensable position in the economic composition of China and is also an important part of ensuring people's living standard.China also holds an absolute position in the pig industry.China has been the world's top pork consumer for 2012-2016,accounting for more than 50%of the world's total consumption.Pig industry is booming,a large number of problems are also highlighted,one of the most concern is the issue of drug resistance.Pigs in the farming are at varying degrees risk of e?pidemic,although improved feeding and management to improve the environmental conditions of pigs can prevent diseases and reduce the incidence of pigs,but due to the external environment long-term existence of some pathogenic microorganisms,once the disease,the necessary treatment Medication is inevitable,even in developed countries such as the United States and the European Union.China is the country with the largest amount of live pigs in the world.large-scale breeding farms occupy a considerable proportion.In a long time to come,the pressure on prevention and control of animal epidemics remains high.The use of veterinary drugs is still the main means of prevention and control of swine disease.Escherichia coli and Staphylococcus,as a large number of Gram-negative bacteria and Gram-positive bacteria that inhabit the environment,although they are resident,but have been exposed to a large number of other bacterias and organisms due to their widespread existence,so usually used as an indicator of the environment.It is precisely because of its unique way of existence.In this paper,Escherichia coli and Staphylococcus are as the research objects,their resistance and resistance genes were detected in order to understand the pig farm antibiotic resistance and drug resistance status.In this study,six types samples about nasal swab,feces,air,soil,water were collected from a pig farm in Jiangsu province,which contain 18 nasal swabs,18 anal swabs and 6 stool samples,9 soil samples,6 water samples,6 air samples total of 67 samples.200 strains of Escherichia coli and 93 strains of Staphylococcus aureus were isolated from them.The antibiotic susceptibility tests of 15 kinds of antibacterials in 7 categories were conducted by agar plate dilution method.The drug-resistant strains were screened then by PCR detect resistance gene of plasmid-mediated,including:polymyxin mcr-1,fosfomycin fosA3,fosC2,and carbapenems blaNDX-1,blaKPC-2,blaVIM-1,blaVIM-2,blaIMP-1,btaIMP-2 and blaOXA-48.The mcr-1 positive strains were selected for conjugation test and MLST was used to detect seven pairs of housekeeping genes for mcr-1 positive strains.The results showed that E.coli and staphylococcus isolated from pig farms were widely resistant and there was a risk of horizontal transmission.Escherichia coli and Staphylococcus isolated from six different environmental samples had different degrees of resistance to 13 kinds of antibacterials,of which all strains were sensitive to amikacin and meropenem,chloramphenicol resistance rates were above 90%.Among them,Escherichia coli has a resistance rate of more than 50%to 7 kinds of antibacterials and concentrates on 6-8 weight drug resistance.Staphylococcus aureus is resistant to 12 kinds of antibacterials less than 25%,only resistant to oxytetracycline,chloramphenicol,florfenicol higher than 90%,and multi-drug resistance concentrated in the 0-2 weight.31 strains of fosfomycin-resistant,35 strains of colistin-resistant and 2 strains of meropenem resistant were detected by PCR,and Successfully detected 19 strains of Escherichia coli with mcr-1,12 strains with fosA3 Of Escherichia coli and 2 strains of staphylococci with mcr-1,suggesting that plasmid-mediated resistance genes are also widespread.After performing 19 mcr-1 positive Escherichia coli conjugation transfer assay,the successful conjugation rate was 36.8%,and MICs of colintin of transconjugants also changed after obtaining mcr-1.The mcr-1 resistance gene splicing experiments showed that mcr-1 resistance gene can be horizontal transmission,and the spread of resistance has a great impact on environment.MLST typing showed that the mcr-1 positive strains were divided into 16 ST types,9 were known,7 were unknown,in 19 strains,14 strains had unique ST,3 strains were ST88,2 strains were ST542,It shows that the current pig farm Escherichia coli is rich in polymorphisms,it need to strengthen the detection of microbial variability and epidemiological investigation. |
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