| Microorganisms and their products in bioaerosol from animal houses can cause serious air pollution. The polluted air in livestock farms is often associated with the outbreak of the epidemic diseases and the environmental problems. E. coli was used as indicator bacterium to test the antibiotic susceptibility and resistant genes of bacteria and their transmission to surrounding environments. Air samples, including indoor and outdoor air(upwind 10 and 50 m as well as downwind 5, 10, 20, 50, 100, 200 and 400 m away) of 5 swine farms were collected using six-stage Andersen microbial sampler and LWC-I. Fresh fecal samples were collected randomly in each swine farm and silt, river, and soil samples were collected at each different site(5, 10, 20, 50, 100, 200, and 400 m away from the outfall of swine farm) for assessment of E. coli.Firstly, through the detection of the concentrations of airborne E. coli and its distribution in each stage of Andersen sampler, the possibly damage of microbiological aerosol to animal or farm workers should be given an enough importance. Secondly, the antimicrobial resistance of E.coli were tested by K-B method and then evaluate the spread of resistant E.coli from feces to surroundings through the comparison of antimicrobial resistance between strains isolated from different samples. Thirdly, the enterobacterial repetitive intergenic consensus(ERIC)-PCR method was applied to amplify the spreading of bioaerosol from animal houses to surroundings. Furthermore, by detecting antimicrobial resistance genes, the situation of antimicrobial resistance in E.coli in animal rear environment were found and could be used as basis for farm workers; and through comparing the differences of the antimicrobial resistance genes in E.coli isolated from different samples, the transmission of antimicrobial resistance genes in E.coli could be found.The results showed that: the content of airborne E.coli in swine house was 17-67 CFU m-3, and the content of respirable airborne E.coli was 11-36 CFU m-3. The aerodynamic diameters of most particulate matter(PM) were very small(<2.5 μm). So, these PM can penetrate into the lower respiratory tract easily. The E.coli strains showed resistance to 14 antibiotics suchtetracycline, nalidixic acid, gentamicin, kanamycin, ciprofloxacin and ofloxacin. 96.97%(160/165) of E.coli presented multi-drug resistant: 11.52%(19/165) of strains showed resistant to 2-5 antibiotics, 56.56%(93/165) of strains showed resistant to 6-10 antibiotics and27.27%(45/165) of strains showed resistant to 11-13 antibiotics. The antimicrobial resistance of E.coli from indoor feces and outdoor surroundings showed high similarity,which proved the transmission of E.coli to surroundings environments. Moreover, 56.67%(17/30) of isolates from indoor air, 61.54%(16/26) of isolates from outdoor air, 60%(15/25)of isolates from river, 45%(9/20) of isolates from soil as well as 57.89%(11/19) of isolates from silt had the same origin with strains from indoor feces.The results showed that resistant bacteria in indoor feces could form aerosol and spread to the outside environment and pollute the nearby air( ≥400m), river( ≥200m), silt( ≥50m),and soil( ≥400m). Strains having ≥90% similarity carried the same resistant genes, which proved the spread of resistant bacteria from indoor feces to outdoor surroundings. The transmission of resistant E.coli could cause the outbreak of the epidemic diseases and be a potential threaten to public environment and human health. |
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