| dc.description.abstract | Generation of bioaerosols containing bacterial pathogens during beef harvesting is an
important issue to consider when controlling pathogens in the meat industry. Pathogens such as
Shiga toxin-producing Escherichia coli (STEC) and Salmonella present on carcasses may be
aerosolized during initial steps of slaughter, where highly active procedures are conducted, and
transferred from these dirty areas to cleaner areas. This may result in the pathogens being
deposited on the meat before the end product is released for sale. In this study, large air samples
(2.8-4.8 m3) were collected from various areas at two large and two small beef harvesting
establishments during the fall spring and summer seasons using a wetted wall cyclone (WWC)
sampler. Samples were tested for STEC and Salmonella and analyzed by direct plating,
automated immunoassay system (Crystal Diagnostic, CDx), and real-time PCR (RT-PCR)
analysis. All positive samples from CDx were confirmed by plating in selective and differential
media followed by biochemical and serological tests, and STEC was confirmed by conventional
PCR. Positive isolates were further confirmed using BAX PCR System. The RT-PCR products
were confirmed by Illumina Sequencing. Based on selective plating, there were no positive air
samples for Salmonella or STEC in the fall season, while air samples from all plants were
positive for Salmonella and STEC in the spring and summer. The recovery of both pathogens
was improved by extending enrichment time from 18 to 36 h. Percentages of positive samples
when enriching for 18 h were 21.4 and 17.9 for Salmonella and STEC, respectively. When
enriching for 36 h, percent positives were 57.1 and 60.7 for Salmonella and STEC, respectively.
The percent positives when testing both Salmonella and STEC by RT-PCR (37.5%, 65.0%) were
significantly higher than CDx with enrichment for 18 h (P<0.05). For 36 h enrichment,
Salmonella percent positives (57.1) by CDx were significantly higher than RT-PCR. While the
percent of STEC positives was not different for either method (60.0%, 65.0%). PFGE analysis
showed that the bacterial DNA from isolates from “dirty” areas was the same as the DNA from
“clean” areas, indicating potential role of the air in transferring bacteria between different areas
of the plant. In conclusion, the outcome of this study will help the meat industry be aware of the
presence of bioaerosols in meat plants and the information will be used to enhance meat plants’
sanitation processes and promote consumers’ health. | en |
