Airborne Salmonella and Listeria associated with Irish commercial beef, sheep and pig plants

- First report to estimate the incidence of Salmonella and Listeria in abattoir air.
- Relates levels of Salmonella and Listeria in abattoir air with carcass contamination.
- Showed higher levels of Salmonella, but no Listeria, in pig abattoir air.
- Observed higher levels of injured pathogens in beef and sheep abattoir air.

Air samples from lairage, hide/fleece pulling or dehairing/scraping, evisceration and chilling areas in commercial beef, sheep and pig plants were examined for Salmonella spp. and Listeria monocytogenes, by impaction or sedimentation onto selective (Brilliant Green Agar, BSA; Listeria Selective Agar, LSA) and non-selective (Plate Count Agar, PCA) media.Both pathogens were frequently detected in all three plants. Improved recoveries were achieved by combining sedimentation, and broth based resuscitation, suggesting cell injury.Salmonella were recovered from all three plants, with the highest counts on BGA in the pig plant. The most common serotypes were S. Typhimurium in the beef/sheep plants and S. Derby in the pig plant.Very low counts of L. monocytogenes (e.g. 2.6 CFU m2) were detected at hide removal on LSA sedimentation plates in the beef plant. These included serogroup 1/2a-3a and 1/2b-3b-7.Pathogen counts in the three plants were generally very low, suggesting that air is unlikely to be a significant source of carcass or plant surface contamination.