The Risk and Thermal Susceptibility of Non-O157 and O157:H7 Shiga-toxin Producing Escherichia coli in Non-Intact Beef Products Intended for Food Service or Retail

<P> Marination and blade tenderization are widely used to enhance the palatability and marketability of underutilized meat cuts. However, the risk of pathogen internalization propagated by blade tenderization and marination been previously documented (Echeverry et al., 2010; Huang & Shen, 2011; Luchansky et al., 2009). Luchansky and colleagues (2009) recovered 33% of the surface inoculum within 1 cm of the muscle surface in blade tenderized products, while Muras and others (2012) observed that when a marination solution inoculated with 105 log CFU/ml O157:H7 was used to marinate beef tri-tip roasts, the pathogen was present at counts greater than 2.0 log CFU/cm2 at 21mm below the meat surface. Furthermore, blade tenderized beef products were implicated in several outbreaks of O157:H7 in the 2000s. While research performed in our lab (Echeverry et al., 2010; Liao et al., 2012; Chancey et al., 2013) and the labs of others (Heller et al., 2007) have demonstrated intervention-based reduction of external pathogens and subsequent translocation, the survival of non-O157 STECs in the internal cores of cooked beef steaks has been documented (Liao et al., 2012; Luchansky et al., 2012). </p> <P> Pathogen resistance to previously considered lethal cook temperatures is of tremendous concern-- especially in non-intact meat products, which despite the recognized risk of pathogen translocation are not currently distinguishable to the consumer. While there exist several genotypic and environmental factors which can influence bacterial expression of thermotolerance, previous research also suggests that simple substrate biochemistry and structure can influence survivability. Ahmed and colleagues (2005) indicated meat composition-namely fat content-influenced the post-cooking survival of O157:H7. Other researchers have demonstrated the influence of other biochemical traits, such as water activity and pH, on the thermal tolerance of pathogenic bacteria (Doyle & Mazzotta, 2000; Carlson et al., 2005). Data regarding the influence of such biochemical traits on the onset of thermotolerance in non-O157 STECs is severely limited. Similarly, the propensity for non-O157 STEC migration and survival in marinated beef systems is not well understood. </p> <P>The objectives of this study were to investigate the internalization and cooking survivability of non-O157 ("Big 6" adulterants) and O157:H7 shiga-toxin producing Escherichia coli in non-intact beef products directed towards retail (marination; Phase One) or food service (blade tenderization; Phase Two). </p>