Detection Of Airbore Aerobic Bacteria And The Occurrence And Spread Of Escherichia Coli Aerosols From Environment Of Pig Houses

Airbore microbes and their products in bioaerosol from animal houses can cause serious air pollution. They may also affect the health and the production capability of the animals and induce prevalence of aerosol infectious diseases. The polluted air in livestock farms is often associated with the outbreak of the epidemic diseases and the environmental problems. Currently, the study of airborne microbes in animal houses mainly concentrated on a specific time period and some pathogenic microbes. There are less studies about the dynamic changes,distribution of airborne microbes throughout the year and the spread of airborne microbes. Therefore, to fully understand the variation and distribution characteristics of airborne microbes in animal houses, from April 2008 to March 2009 , detection airbore aerobic bacteria in enclosed and semi-enclosed pig houses which are the most common pig houses in Shandong province were detected, and analyzed the airborne distribution characteristics and evaluated its potential health threats. Meanwhile, to understand the spread of microbial aerosols, antibiotic susceptibility and enterobacterial repetitive intergenic consensus(ERIC) of the indicator bacterium, Escherichia coli(E. coli), were used to analyze the similarity of isolated E.coli strains from feed, feces, indoor and outdoor air samples.From March 2008 to February 2009, sampling was conducted in enclosed pig house and semi-enclosed pig house by Andersen-6 grade air sampler, using 5% blood agar as medium; then we analyzed airborne aerobic bacterial content and size distribution characteristics through counting colonies. The concentration of airborne aerobic bacteria in enclosed pig house fluctuated between 9.07×10~4 and 28.23×10~4 CFU /m~3 (Colony Forming Unit /m~3) and the concentration of airborne aerobic bacteria in semi-closed pig house fluctuated between 12.02×10~4 and 24.95×10~4 CFU /m~3, which reached summit in winter and bottom in summer. Airborne aerobic bacteria mainly centered on the A-D grade, the least on the F grade. The concentration of airborne aerobic bacteria in pig house was high and dynamic; around 4.0×10~5 CFU and 4.9×10~6 CFU of airborne aerobic bacteria could be inhaled into the small bronchia or even directly invaded into bronchic cell each day respectively, which posed potential threats to human and pig health. Ten E.coli isolates from each sample site the same working day were used to test antimicrobial susceptibility by Kirby-Bauer method. Twelve antibiotics were selected: norfloxacin (NOR), cefoperazone (CFP), chloromycetin (CMP), complex sulfanilamide (SXT), gentamycin (GEN), streptomycin (STR), tetracycline (TET), rifampicin (RIF), erythromycin (ERY), penicillin (P-G), tobramycin (TOB) and furantoin (Ni). The results showed that all E.coli strains isolated from indoor and outdoor (downwind 10, 50, 100, 200 m) air samples in the pig house were resistant to RIF,ERY and P-G. It could be concluded that indoor microbial aerosols include antibiotic resistance bacteria could spread to surroundings by air exchanging and cause microbiological contamination.To understand the spread of microbial aerosols in pig houses using E. coli as indicator, the airborne E. coli in 4 pig houses and their surroundings at different points 10, 50 m upwind and 10, 50, 100, 200 and 400 m downwind respectively from the pig houses were collected, and the concentrations were calculated at each sampling point. Furthermore, the feces of pigs were collected to separate E. coli. The ERIC-PCR technology was used to amplify the isolated E. coli DNA samples, then the amplified results were analyzed by NTSYS-pc (Version 2.10) to identify the similarity of isolated E. coli. The results showed that the airborne E. coli concentrations in indoor air of the 4 pig houses (21-35 CFU m~-3 air) were much higher than those in upwind and downwind air(P<0.05), but there were no significant differences (P>0.05) at downwind distances. The ERIC-PCR results also showed that 52.4% of the fecal E. coli (four houses being respectively 2/4, 50%; 2/4, 50%; 3/6, 50%; 4/7, 57.1%) were identical to the indoor airborne E. coli isolates, and there was more than 90% similarity between the majority of E. coli (55%) isolated from downwind air at 10, 50, 100 and 200 m and those from indoor air or feces. It could be concluded that the aerosols in pig houses can spread to the surroundings, and thus effective measures should be taken to control and minimize the spread of microbial aerosols.