| In this study,a closed laying hen farm in Suning City,Hebei Province was selected as the sampling site.From October to December 2019,at the beginning,middle and end of each month,use RC-4HC thermometer and hygrometer and large-capacity air sampler(Huarui Hean Technology)to continuously conduct air aerosol in a closed layer house.For testing and sampling,the feed,feces and soil samples in the chicken house were collected at the same time.Through metagenomics and real-time fluorescent quantitative PCR(q PCR)detection technology,the diversity,relative content and content of antibiotic resistance genes(ARGs)in the four environmental media in the laying hen house.The distribution characteristics were analyzed and discussed,focusing on the pollution of ARGs in feed and air particles.The study first found that resistance gene pollution is widespread in four environmental media through metagenomics technology.In the layer house,the soil has the highest abundance of resistance genes,followed by air particles.Tetracycline resistance genes are ARGs with the highest relative abundance in air particulate matter,soil and feed,and the relative abundance in feed even reaches 99.38%.The proportion of air particles is 78.30%,which may be related to the large amount of tetracycline drugs in the farm.Florfenicol resistance genes are the most abundant ARGs in the soil,with an abundance of 38.85%.Then we tested the microbial population diversity and relative content in the four environmental media,and analyzed the differences between the groups,and found that the differences between the four groups were not significant.The air particles are rich in flora,and the dominant flora is the potential pathogenic bacteria that carry a large amount of ARGs in the human body.In the second experiment,we selected 6 ARGs for relative quantitative analysis based on the analysis results of metagenomics and the use of antibiotics in the farm.The results showed that the copy numbers of different resistance genes in feed were different,and the overall range was(6.10±0.41)× 104 ?(1.43±0.03)× 107 copies/g.Among them,lun A is the dominant gene,which is significantly different from other genes(P<0.05);the difference between tet W gene and sul1 gene is significant(P<0.05),and there is no significant difference between the other genes(P>0.05).The overall range of copy number of resistance genes in air particles is(5.32±0.02)× 103 ?(1.15±0.63)× 107 copies/g,which is similar to the relationship between resistance genes in feed.What's more,lnu A is the dominant gene in air particles,and other resistance genes are significantly different(P<0.05),and the remaining resistance genes are not significantly different.In soil,lnu A is the dominant gene in soil,which is significantly different from other resistance genes(P<0.05);there is no significant difference between sul1 and erm B genes,and the relative copy numbers of the two genes are significantly lower than other resistance genes The difference between genes and resistance genes of the same type was not significant(P>0.05),and the other differences were significant.In feces,tet Q gene is the dominant gene,which is significantly different from other resistance genes(P<0.05);lnu A and erm F genes are not significantly different(P>0.05),but they are significantly different from sul1 gene(P<0.05)There was no significant difference between erm F and sul1 resistance genes(P>0.05).The four media all have the problem of resistance gene pollution.The tetracycline resistance gene pollution in the feed is the most serious,the soil has the highest abundance of resistance genes,followed by air particulate matter.The presence of pathogenic bacteria in air particles is the dominant flora,which requires attention to epidemic prevention.There is a significant correlation between ARGs with different mechanisms of action,suggesting that the synergy between ARGs promotes their spread. |
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