Transmission identification of Escherichia coli aerosol in chicken houses to their environments using ERIC-PCR

In order to study E. coli aerosol spreading from chicken houses to their surrounding air, air samples, including indoor and outdoor air (upwind 10 and 50 m as well as downwind 10, 50, 100, 200 and 400 m away) of 5 chicken houses were collected using six-stage Andersen microbial samplers and Reuter-Centrifugal samplers (RCS). E. coli concentrations (CFU/m(3) air) collected from different sampling sites were calculated. E. coli strains from chicken feces samples were also isolated. Furthermore, the enterobacterial repetitive intergenic consensus (ERIC)-PCR method was applied to amplify the isolated E. coli strain DNA samples. Through the genetic similarity analyses of the E. coli obtained from different sampling sites, the spreading of bioaerosol from animal houses to the ambient air was characterized. The results showed that the isolated E. coli concentrations in indoor air (9–63 CFU/m(3)) in 5 chicken houses were higher than those in upwind and downwind air, but there were no significant differences between the indoor and downwind sites 10 m away from all the 5 houses (P>0.05). The phylogenetic tree indicated that a part of the E. coli (34.1%) isolated from indoor air had 100% similarity with those isolated from feces, and that most of E. coli isolated (54.5%) from downwind at 10, 50, 100 or even 200 m had 100% similarity with those isolated from indoor air or feces too. But those isolated from upwind air had a lower similarity (73%–92%) with corresponding strains isolated from indoor air or feces. Our results suggested that some strains isolated from downwind air and indoor air originated in the chicken feces, but most of isolates obtained from upwind air samples did not come from the chicken feces or indoor air. Effective hygienic measures should be taken in animal farms to prevent or minimize downwind spreading of microorganism aerosol.