The Characteristics Of Antibiotic Resistance Genes In The Atmospheric Environment Of Animal Manure Composting

In recent years,antibiotics have been overused in the breeding industry,inducing the rapid growth of Antibiotic Resistance Genes(ARGs)and Antibiotic Resistance Bacteria related to animals in the farm.Animal manure was considered to be an important source of ARGs pollution in the environment.If ARGs was transferred to human pathogenic bacteria(HPBs),it would cause the failure of antibiotic treatment and ultimately threaten human health.Manure composting was considered to be one of best way to reduce the introduction of ARGs into the environment.However,the possible pollution of ARGs in the atmospheric environment of composting plants is unknown.During movement of the composting material,including shredding,compost pile turning,and compost screening,microorganisms could be aerosolized and thus released into the atmospheric environment.In the light of of these problems,this study detected the concentration of ARGs in the air of different composting plants,and analyzed the diameter distribution characteristics of ARGs in the air of different operation units.The results of this study provide the essential data for the assessment of air pollution characteristics and ecological risks of composting plants.Firstly,dynamic concentrations of 16S rDNA,2 HPBs(Escherichia coli.and Staphylococcus spp.),1 mobile gene element(intI1),7[3-lactam resistance genes(blaCARB-4,blaOXA-18,blaOXA1,blaOXA?,blaOXA? blaPSE,blaTEM*),10 tetracycline resistance genes(tetQ tetM,tetS,tetT,tetW,tetA/P,tetG,tetL,tetZ,tetX),4 sulfonamides resistance genes(sul1,sul1,sul3,dfrA1),and 1 erythromycin resistance gene(ermB)using droplet digital PCR,and bacterial communities around atmospheric environment of composting plant were also investigated by sequenced.In this study,the target genes of intl1 and all 22 ARGs(except tetO)were detected in air of composting,packaging,office,and downwind areas.The highest concentration of airborne ARGs was detected in the packaging areas and airborne intl1 had the maximum average concentration of 104 cupies/m3,with up to(1.78 ±0.49)× 10-2 Copies/16S rDNA copy.Due to manipulation of the fresh and compost materials,ARGs and antibiotic-resistant bacteria could be aerosolized and then be dispersed to atmospheric environment of office and downwind areas through the air.The 5 dominant phyla in the 5 sampling sites were commonly Firmicutes,Proteobacteria,Bacteroidetes,Chloroflexi and Actinobacteria.Firmicutes and Proteobacteria were the major phyla inside(C,P,and 0)and outside(U and D)of the composting plants,respectively.Redundancy analysis of ARGs,HPBs,and bacterial components indicated that the bioaerosol pollutant pattern in packaging areas was most similar to that in composting areas,followed by office,downwind,and upwind areas.The co-occurrence of ARGs and bacterial taxa implied that aerosolized ARG fragments from composting and packaging areas contributed to the compositions of ARGs erosols in office and downwind areas.The results presented here show that composting plant is a source of ARGs emissions in atmospheric environments.ARGs can be used as indicator pollutants for the escape of microorganisms in composting plants,which can effectively track the bioaerosols released by composting plants.The diameter of biological particles in the air is an important index to evaluate their harm to human.We studied on the size distribution of ARGs in the air for different operation units of our composting plant.It was found that the concentration of the resistance gene was mostly related to the diameter,and the concentration of the target gene increased with the increasing of the diameter.Among them,distribution characteristics of total bacteria and ARGs in composting area,packaging area and office area are not completely consistent.The highest concentration of target genes loaded from eight particles was detected in the packaging area,followed by the composting area,fresh waste area,office area and downwind area.Diameter distribution of resistance genes in different operating units was different,and the relative high concentration of resistance genes was detected on particles with large size.Totally,the target gene was mainly deposited in the human nose.It was worth noting that the concentration of some target genes detected in the fresh waste area was high on the small diameter particles and could deposited in the lung,which has a high potential risk to human health.The results of current study would contribute to accurately estimate the depositing position of antibiotic resistance genes in the air of composting plants and risks to workers' healthy.