Detection of Escherichia coli O157:H7 and Salmonella enterica in air and droplets at three U.S. commercial beef processing plants.

Bacteria are known to be present in the 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, and Enterobacteriaceae counts 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 from locations that were not contacted by droplets. Higher pathogen prevalences, aerobic plate counts, and Enterobacteriaceae counts 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.