Purpose: The association of various virulence genes associated with the enterohemorrhagic pathogen, Escherichia coli O157, was examined in beef trim and variety meats to determine if there were a regular relationship between their frequencies of occurrence in these products. Such information could be useful for risk assessments and for designing sampling and testing plans to maximize the frequency of detection of pathogens in beef-based meat products.
Methods: Samples (375g) were collected during 2012, enriched for at least 8 hours and screened by PCR for the virulence-associated genes rfb, eae, stx1, and stx2 and by lateral flow to detect the O157 antigen. Also, two Salmonella-specific genes were detected. From plants that tested both product forms, 301,786 and 14,648 samples of trim and variety meats, respectively, were analyzed.
Results: Enterohemorrhagic E. coli (stx+ and eae+) screen-positive sample frequencies for trim and variety meats were 12.9% and 19.1, respectively. Generally, contamination rates of variety meats were higher than rates for trim. However, while the frequency of occurrence of E. coli O157- and Salmonella-associated genes in beef samples was strongly correlated, the strength of association of O157-specific targets between trim and variety meats was highly variable during the year though tending to be higher during the warmer months.
Significance: Even though virulence-associated genes occur in samples more frequently during late spring and early summer months, there is no consistent relationship between their prevalence in trim and variety meats. Future analyses might consider differentiating between types of variety meats. However, both product types should be monitored and these observations might be considered in microbial hazard risk assessments.