MONITORING OF PATHOGENIC BIOAEROSOLS IN BEEF SLAUGHTER FACILITIES BASED ON AIR SAMPLING AND AIRFLOW MODELING

Salmonella and Shiga toxin producing Escherichia coli (STEC) have long been recognized as pathogens of concern in meat products due to the prevalence of these microorganisms in the gastrointestinal tract and hide of livestock. Bacterial ingestion due to contaminated food products causes a great economic burden from the hospitalization and death of those who become infected. Recently, aerosolized bacteria have been recognized as a threat to human health and shelf life of food. In beef processing facilities, the majority of harmful bacteria are introduced by the cattle. Heating, ventilation, and air conditioning (HVAC) systems can harbor and transport these microscopic organisms. Salmonella and STEC cause 78 billion dollars lost every year due to contaminated food. During the harvesting process, these pathogens may become aerosolized from the carcasses by various mechanisms, including worker activity and airflow from HVAC systems. Although bacteria are robust creatures, environmental conditions including ventilation can be manipulated to disrupt their proliferation. In this study, one rural and one small beef facility were examined. High air volume wetted wall cyclone bioaerosol samplers capable of collecting and concentrating bioaerosols in a liquid effluent were used during the entire processing at bleeding, de-limbing, de-hiding, washing, and chiller locations. Bioaerosols were analyzed using microbial plating, quantitative Polymerase Chain Reaction, and microbiome analysis. Total bacteria counts, STEC, and Salmonella concentrations were enumerated in the air and critical areas were identified. Salmonella and STEC were found to increase with each passing day in the facility, as well, total counts and STEC increased between morning and afternoon phases of processing. Significant differences in total counts and temperature were found at different locations in the facilities. Blueprints were obtained from the examined facilities and the cattle processing floors were modeled using computational fluid dynamics. The airflow created from the HVAC systems was found to have a significant effect on the spread of bioaerosols. Similarities were found between the collected concentrations of bioaerosols and particle traces in the modeled facilities. Finally, new ventilation models were generated to significantly increase the sanitation of the beef slaughtering process.