Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 17, 2010
Publication Date: September 1, 2010
Citation: Brooks, J.P., McLaughlin, M.R., Scheffler, B.E., Miles, D.M. 2010. Microbial and antibiotic resistant constituents associated with biological aerosols and poultry litter within a commercial poultry house. Science of the Total Environment. 408:4770-4777. Interpretive Summary: Modern large-scale poultry rearing provides an ideal environment for harboring disease causing bacteria in the house bedding (litter). While it is understood and assumed that there will be a significant presence in the litter, it is largely not understood the impact on poultry house air. The purpose of this study was to determine the presence of common poultry antibiotic-resistant and pathogenic bacteria in the litter and air environment following a typical flock cycle. In litter, it was determined most measured bacteria followed a pattern of incremental increasing as the flock cycle progressed and subsequent decreasing when chickens were removed. This trend remained true for the aerosol environment as well; though aerosolized bacteria were more concentrated inside, they were far less concentrated outdoors, which may indicate that very few survive or are being released outside. Antibiotic resistance patterns were determined for select bacteria and overall most were found to have resistance to only a few antibiotic classes. Very few were found to be multi-class resistant. Overall, antibiotic resistance did increase as the time progressed from no chickens to directly prior to the sell-out period. It’s not understood at this time what, if any, problems exist due to aerosolized antibiotic resistant bacteria in the poultry house, but workers should practice hygienic practices such as wearing masks and gloves while in the house.
Technical Abstract: Poultry are known to harbor antibiotic resistant and pathogenic bacteria, and as such poultry litter and poultry house air can be contaminated with these bacteria. Health researchers have typically focused on the presence of aerosolized endotoxin, NH3, and particulate matter within poultry houses; however the presence of antibiotic resistant bacteria in biological aerosols is largely not understood. The purpose of this study was to determine the amount of aerosolized bacteria, particularly fecal indicators, staphylococci, and enterococci, associated with poultry house and outdoor air. Aerosol samples were collected using SKC Biosamplers in triplicate at multiple locations on the farm and in the house. Antibiotic resistance was investigated using the Kirby Bauer method on selected isolates using twelve different antibiotics spanning both narrow to broad spectrums of effectiveness. Overall there was a cyclical increase in bacterial concentrations as flocks progressed from pre-flock to late-flock, with >2 orders magnitude lower concentration during pre-flock periods (no chickens), in both the litter and aerosol samples. It was interesting to note that samples collected at the end of the house (near exhaust fans) produced counts approximately 1 order magnitude greater than samples collected in the center of the house. Overall, endotoxin followed similar trends with increases at the fan end of the house and dependent on flock cycle stage. The house environment provided for significantly concentrated endotoxin levels; most were similar to other poultry houses and sheds described in the literature. It was estimated that Staphylococcus and Enterococcus bacteria accounted for at least 90% of cultured aerobic bacteria. Rarely was an isolate resistant to more than 4 antibiotic classes; however, there was a trend upwards in overall resistance of select organisms as the flock cycle progressed. It appears that although levels of antibiotic resistant bacteria were highly concentrated within the house, levels were much lower outside of the house, and very little house escape occurred. Simple use of hygienic masks and gloves would limit the amount of interaction between workers and any poultry litter associated bacteria, be it aerosol or litter contact.