title: Comparison of the type and number of microorganisms and concentration of endotoxin in the air of feedyards in the Southern High Plains.
abstract: OBJECTIVE
  To determine the bacterial, fungal, and endotoxin concentrations in aerosolized ambient air during the winter and summer in feedyards located in the Southern High Plains, identify aerosolized microbial pathogens, and determine the size of microbial and dust components.
  
  
  METHODS
  Aerosol samples were obtained from 7 feedyards.
  
  
  METHODS
  Aerosol samples were collected upwind, on-site, and downwind from each feedyard at a point 1 m above the ground by use of biological 2- and 6-stage cascade impactors.
  
  
  RESULTS
  Significantly more microbes were cultured from on-site and downwind samples than upwind samples. There were significantly more microbes during the summer than during the winter. However, mean endotoxin concentration was significantly higher during the winter (8.37 ng/m3) than the summer (2.63 ng/m3). Among 7 feedyards, mean +/- SE number of mesophilic bacteria (1,441 +/- 195 colony-forming units [CFUs]/m3) was significantly higher than mean number of anaerobic bacteria (751 +/- 133 CFUs/m3) or thermophilic bacteria (54 +/- 10 CFUs/m3) in feedyard air. Feedyard aerosol samples contained more mesophilic fungi (78 +/- 7 CFUs/m3) than thermophilic fungi (2 +/- 0.2 CFUs/m3). Eighteen genera of bacteria were identified by use of an automated identification system.
  
  
  CONCLUSIONS
  It appeared that gram-negative enteric pathogens offered little risk to remote calves or humans via ambient aerosols and that gram-positive pathogens of the Bacillus, Corynebacterium, and Staphylococcus spp can be spread by aerosols in and around feedyards. It was common to detect concentrations of endotoxin in the ambient air of 7 feedyards.
authors.affiliation: USDA-Agricultural Research Service, Conservation and Production Research Laboratory, 2300 Experiment Rd, Bushland, TX 79012, USA.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Purdy
authors.forename: David C
authors.initials: DC
authors.lastname: Straus
authors.forename: David B
authors.initials: DB
authors.lastname: Parker
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Wilson
authors.forename: R Nolan
authors.initials: RN
authors.lastname: Clark
mesh_terms: D000391:Air Microbiology; D000704:Analysis of Variance; D001419:Bacteria / Q000302:isolation & purification; D044822:Biodiversity; D004731:Endotoxins / Q000032:analysis*; D005658:Fungi / Q000302:isolation & purification; D012621:Seasons; D013781:Texas; D014887:Weather
chemical_list: D004731:Endotoxins