Growth of Shiga toxin-producing Escherichia coli (STEC) and impacts of chilling and post-inoculation storage on STEC attachment to beef surfaces.
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Concern has been expressed surrounding the utility of studies describing the efficacy of antimicrobial interventions targeting the Shiga toxin-producing Escherichia coli (STEC) that inoculate chilled versus non-chilled beef carcasses. The objectives of this study were to evaluate the effects of chilling (non-chilled, chilled to surface temperature of 5C) on STEC attachment to brisket surfaces, and the effects of post-inoculation storage on STEC recovery. Paired briskets from split carcasses were separated; one brisket from each pair was kept non-chilled, while the other was chilled to a surface temperature of 5C prior to inoculation. Briskets were inoculated with a cocktail of eight STEC and then stored at 5 or 25C. At 0, 30, 60, 90 and 120min post-inoculation, 30cm(2) of tissue was aseptically excised, followed by selective enumeration of strongly and loosely attached STEC. A significant, though small (0.4 log10CFU/cm(2)), difference in the numbers of strongly attached cells was observed between non-chilled and chilled briskets (p<0.05). Significant effects on cell attachment by the interaction of chilling and post-inoculation storage period, or chilling and post-inoculation storage temperature, were identified (p<0.05). Results indicate beef chilling and post-inoculation storage conditions influenced STEC attachment to beef.