Purpose: The purpose of this study was to conduct a 6 month longitudinal study to monitor Escherichia coli O157:H7, S. enterica and L. monocytogenes contamination patterns and identify potential harborage sites in a small and very small fresh meat plant.
Methods: Both plants were sampled during mid-shift operation on a monthly basis. A total of 330 environmental sponge samples were collected from up to 55 sites (3 sponge swabs were collected to allow testing for each pathogen) in each facility. Samples collected included food contact surfaces (e.g., tables, scales, bins), non-food contact surfaces (e.g., walls, drains, sinks), and beef carcasses. Samples were microbiologically analyzed to isolate and detect S. enterica, E. coli O157:H7 and L. monocytogenes, following modified versions of the U.S. Department of Agriculture Microbiology Laboratory Guidebook protocols 4.05, 5.05, and 8.07, respectively.
Results: S. enterica was isolated from 15 (4.5%) and 8 (2.4%) samples from Plant 1 and Plant 2, respectively. S. enterica was recovered more than once from 2 sites in Plant 1. E. coli O157:H7 was detected in 1.2% of samples in Plant 1, but was not recurrently isolated from a single site. E. coli O157:H7 was not isolated from Plant 2. L. monocytogenes was isolated from 17% of the samples from Plant 1 and 1.2% of samples from Plant 2. Recurrent isolation of L. monocytogenes from 15 sites was observed in Plant 1, while no single site in Plant 2 repeatedly tested positive for L. monocytogenes.
Significance: Our findings suggest that L. monocytogenes has higher prevalence than S. enterica and E. coli O157:H7 in the fresh meat processing plant environment. While L. monocytogenes may persistently contaminate the environment of fresh meat processing plants, E. coli O157:H7 and S. enterica contamination seems to be mostly sporadic.