Occurrence And Transmission Of β-RGs In The Livestock Farm

The prevalence of antibiotics resistance genes(ARGs)has been identified as an emerging environmental contaminant that poses considerable risk to human health.Moreover,the transmission to human health through agriculture was more widespread than clinical medicine of ARGs.The β-lactam antibiotics(β-Ls)were largely used for the subtherapeutical and treatment of mastitis in dairy cows.While the highest abundant were β-lactamase resistance genes(β-RGs)of total ARGs in dairy farms that could enter the food chain as high-risk resistance genes.However,there were few studies on the mechanisms of ARGs transmission in agriculture and livestock.To figure out this issue,we investigated the surrounding environment of the Dulburt Mongolian autonomous region(Dumont)livestock farms by the geographic information system(GIS).Besides,we tracked the abundance of ARGs,mobile genetic elements(MGEs),and microbial community in different environmental medias(soil,surface water,feces,meal,and milk).Finally,statistical analysis was used to infer the transmission mechanisms and pathways of β-RGs from livestock farm to the human food chain.In combination with GIS optimized deployment,the samples of 10-cm depth soil(T01T32),50-cm depth soil(T33-64),surface water(W01-W05),feces,meal,and milk were collected in the livestock farm.The relative abundance of ARGs and MGEs was detected by RTqPCR and contamination comprehensive ranked by principal component analysis.The metagenome assembly and annotation of microbial communities by DNA extraction,library construction,and inspection.The correlation analysis of ARGs,MGEs,and microbial community were according to Pearson correlation.Furthermore,the transmission and pathways of β-RGs were discussed.Result:The relative abundance of β-RGs in the Dumont livestock farm accounted for 97%of all ARGs,which blaTEM and cfxA accounting for almost 98%of the β-RGs.The relative abundance of blaTEM in β-RGs was more than 98%for meal,50-cm depth soil,water,and milk.While the cfxA was highest in feces(90%)but in 10-cm depth soil(51%)samples with a decreasing proportion.In all samples,the highest relative abundance for microbial communities was Proteobacteria(46.35%)and Bacteroidetes(26.68%)of the phylum.In addition,the microbial communities correlated with ARGs were clustered and divided into four frames through the Pearson correlation.blaTEM with Pseudomonadales(9.62%)-Pseudomonadaceae(12.89%)-Pseudomonas(15.36%);Enterobacterales(21.62%)-Erwiniaceae(24.48%)Pantoea(29.02%),Curtobaterium(8.02%)was extremely significantly correlated(P<0.001).blaTEM significantly correlated(P<0.01)with Gammaproteobacteria(33.51%).blaTEM was correlated(P<0.05)with Proteobacteria(46.35%),Micrococcales(12.51%),Microbacteriaceae(11.61%).cfxA was extremely significantly correlated(P<0.001)with Bacteroidales(23.96%)-Bacteroidaceae(12.89%)-Bacteroides(15.39%),Spirochaetes(1.82%)-Spirochaetia(2.21%),Prevotellaceae(7.24%)-Prevotella(7.86%),Alistipes(4.74%).And cfxA was significantly correlated(P<0.01)with Bacteroidia(21.37%).cfxA was correlated(P<0.05)with Firmicutes(4.77%).Obviously,the main host were Proteobacteria and Bacteroidetes of bla TEM and cfxA.The Proteobacteria were mainly distributed in meal(82.94%)surface water(38.39%)10-cm depth soil(32.67%)and 50-cm depth soil(26.98%)and the Bacteroidetes were mainly distributed in feces(56.48%)10-cm depth soil(20.24%)and 50-cm depth soil(26.65%).The MGEs of β-RGs carrier in all environmental mediums were intI1(2.2%)、intI2(0.66%),intI3(0.18%)tnpA-01(30.89%)、tnpA-O2(0.86%)、tnpA-03(1.48%)、tnpA-04(7.04%)、tnpA-05(0.14%)、tnpA-06(3.62%)、tnpA-07(48.73%)、Tn916/1545(0.14%)、IS613(1.01%)、TRA-A(0.01%)and TRB-C(1.46%).According to Pearson correlation analysis indicated that might be the main hosts of tnpA-03,and tnpA-04 carrying blaTEM in milk and meal.While Bacteroidetes were the main hosts of Tn916/1545,IS613 carrying cfxA in feces.In doing so,we deciphered the host and route of β-RGs transmission from farm to milk which laid the foundation for the risk evaluation of ARGs transmission in the ecosphere.