Microbial Community Characteristics And Antibiotic Resistance Genes(ARGs) Of Microbial Aerosol In Different Livestock Houses

The microbial aerosol contains a large number of pathogens,viruses,fungi,other harmful organisms and the antibiotic resistance genes?ARGs?in livestock houses.The pathogenic factors can be spread by air in the external environment,causing harm to both animal and human health.At present,there is few report on the microbial community structure and the differences of antibiotic contamination in the aerosols from different animal houses.To understand characteristics of microbial community structure and ARGs contamination within the indoor aerosol,it is the important premise to solve the problems of air contamination,disease prevention and disease control in different animal houses.Therefore,in this research the air samples were collected from 12 animal farms includes four swine,four poultry,four bovine.The traditional culture method was used to detect and evaluate particle concentrations and size distributions of airborne aerobes and fungi in different animal houses.The high-throughput sequencing technology was used to analyze the microbial community structure and pathogen content.The ARGs and the class 1 integron of the aerosol samples were detected by polymerase chain reaction?PCR?and quantitative polymerase chain reaction?qPCR?.The results indicated that the microbial contamination in the poultry house was the most serious,the concentration of aerobic bacteria ranged from 7.514×10³ CFU m^-3 to 23.13×10³ CFU m^-3.Then next were the piggery and the cowshed,which were ranged from 8.621×10³ CFU m^-3 to 14.579×10³CFU m^-3 and 1.805×10³ CFU m^-3 to3.243×10³ CFU m^-3,respectively.The highest concentration of airborne fungi ranged from 1.813×10³ CFU m^-3 to 7.550×10³ CFU m^-3 was in hen house,then followed by the piggery and the cowshed,ranged from 1.401×10³ CFU m^-3 to 5.441×10³ CFU m^-3,1.752×10³ CFU m^-3 to 2.367×10³ CFU m^-3,respectively.The airborne aerobes were mainly distributed in?,?,and?level,accounted for about 79.85%?swine?,73.79%?poultry?,68.63%?cattle?,and the aerodynamic diameter was bigger than 3.3?m.However,the distributions of airborne fungi were different from each other,airborne fungi were mainly distributed in?level in the piggery,accounted for approximately 43.04%,its aerodynamic diameter was greater than 3.3?m;In the hen houses,airborne fungi were mainly distributed in?and?level with about 51.61%,the aerodynamic diameter was from 3.3 to 7.0?m;But particles were mainly distributed in?and?level in the cowshed,constituted 52.52%,its aerodynamic diameter was from 1.1 to 4.7?m.In this research,408,996 effective Tags were obtained using high-throughput?Illumina HiSeq?sequences,33 phyla and 614 genera were obtained by annotation and cluster analysis.At the phylum level,Firmicutes,Actinobacteria,Proteobacteria and Bacteroidetes were the most abundant in aerosol samples from these three kinds of livestock houses.At the genus level,Faecalibacterium,Streptomyces,and Micromonospora were the dominant species in the poultry house;Clostridium,Lactobacillus and Terrisporobacter were the predominant genera in the piggery;The dominant bacteria were Ruminococcaceae,Acinetobacter,Pantoea in the cowshed.There were significant differences in the relative abundances of different aerosol samples from different livestock houses.Meanwhile,there were also certain differences in the pathogenic content from different animal houses,the highest pathogenic content is from swine farm,which make up to 19.52%,then next is from the cowshed with 12.06%,followed by poultry house,constituting 4.22%.In addition,the diversity of microbial flora in aerosols was correlated significantly with the concentration of suspended particles and noxious gas in the animal house.Eight tetracycline resistance genes and the class 1 integron were analyzed by ordinary PCR,the results showed that tetG,tetM,tetO,tetQ,tetW,tetZ and intI1 were detected in three kinds of animal houses,tetA was detected only in the poultry house,and tetB was detected only in the piggery.The abundances of six tetracycline resistance genes?tetG,tetM,tetO,tetQ,tetW,tetZ?and intI1 were analyzed by real-time PCR,the result showed that there were significant differences among different animal houses.The content of tetracycline resistance genes was from7.52×10² to 1.75×10⁶ copies ng^-1·DNA in piggery;It was from 1.11×10³ to 2.02×10⁵copies ng^-1·DNA in cowshed;In poultry house it is from 3.29×10³ to 7.68×10⁵ copies ng^-1·DNA.The highest abundance of intI1 was 6.24×10⁴ copies ng^-1·DNA from piggery;Secondly,it was 2.78×10⁴ copies ng^-1·DNA from poultry house;The lowest abundance of intI1 was 1.30×10⁴ copies ng^-1·DNA from cowshed.The microbial aerosol of livestock houses can be used as a repository for pathogens and resistance genes.There are significant differences in the concentration of pathogens and ARGs in the air of different livestock houses.Therefore,it is of great significance to reduce livestock environmental pollution to the surrounding environment by adopting different environmental control,disease prevention and disease control measures according to the different types of livestock and poultry breeding.