Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2012
Publication Date: 12/1/2012
Citation: Schmidt, J.W., Arthur, T.M., Bosilevac, J.M., Kalchayanand, N., Wheeler, T.L. 2012. Detection of Escherichia coli O157:H7 and Salmonella enterica in air and droplets at three U. S. commercial beef processing plants. Journal of Food Protection. 75(12):2213-2218.
Interpretive Summary: The presence of airborne Escherichia coli O157:H7 and Salmonella enterica at beef processing plants could contaminate carcasses or final products. To determine the prevalences of airborne Escherichia coli O157:H7 and Salmonella at beef processing plants and to identify processes responsible for their generation, air samples were obtained from different areas of three beef processing plants. Airborne E. coli O157:H7 and Salmonella were rarely detected in hide-off areas of the plant and were never detected in carcass fabrication areas where final products were produced. E. coli O157:H7 was detected in 15.8% and Salmonella was detected in 16.5% of samples obtained from initial processing areas of the harvest floor, especially near automated hide-pullers. These data indicate that the process of hide removal occasionally generates droplets that may contaminate adjacent carcasses with pathogens.
Technical Abstract: Bacteria are known to be present in air at beef processing plants but published data regarding the prevalences of airborne Escherichia coli O157:H7 and Salmonella enterica are very limited. To determine if airborne pathogens were present in beef processing facilities, we placed sedimentation sponges at various locations in three commercial beef plants that processed cattle from slaughter through fabrication. For the 291 slaughter area air samples, E. coli O157:H7 was isolated from 15.8% and S. enterica from 16.5%. Of the 113 evisceration area air samples, E. coli O157:H7 was isolated from only one sample and S. enterica was not isolated from any sample. Pathogens were not isolated from any of the 87 air samples from fabrication areas. Pathogen prevalences, aerobic plate counts (APC) and Enterobacteriaceae counts (EBC) were highest for air samples obtained from locations near hide removal operations. The process of hide removal disperses liquid droplets which may contact neighboring carcasses. Samples were obtained both from hide removal locations that were close enough to hide pullers to be contacted by droplets and locations that were not contacted by droplets. Higher pathogen prevalences, APC, and EBC were observed at locations with samples contacted by the hide removal droplets. We conclude that the hide removal processes likely introduce pathogens into the air via a dispersion of liquid droplets and that these droplets may be an underappreciated source of hide-to-carcass contamination.