Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2011
Publication Date: 1/1/2012
Citation: Luchansky, J.B., Shoyer, B.A., Call, J., Schlosser, W., Shaw, W., Bauer, N., Latimer, H., Porto-Fett, A. 2012. Fate of shiga-toxin producing 0157:H7 and non-0157:H7 Escherichia coli cells within blade-tenderized beef steaks after cooking on a commerical open-flame gas grill. Journal of Food Protection. 75:62-70. Interpretive Summary: The USDA/FSIS considers Shiga toxin producing cells of Escherichia coli O157:H7 (ECOH) as an adulterant in raw, non-intact beef, that being both raw ground beef and raw whole muscle cuts that are tenderized via blades, injection, restructuring, and/or vacuum tumbling. There have been requests from consumer interest groups and other food safety organizations for USDA/FSIS to also include non-O157:H7 Shiga toxin producing E. coli (STEC), such as serotype O26, O45, O103, O111, O121, and/or O145 strains, as adulterants in raw, non-intact beef. Although surveys have shown that the prevalence and levels of ECOH and STEC in meats are quite low, both pathogen types continue to cause serious illness due to ingestion of contaminated foods, including meats. Several studies have been published to quantify the transfer and destruction of ECOH, but not STEC, in non-intact beef. Thus, we comparatively evaluated the fate of both ECOH and STEC in blade tenderized streaks following cooking on a gas grill. Our findings established that blade tenderization transfers cells of ECOH and STEC deep into the interior of beef and that proper cooking appreciably reduces the levels of Shiga toxin-producing E. coli in chemically tenderized meat, but does not completely eliminate the pathogen due to non-uniform heating. Our findings will be useful to estimate the comparative risk between intact and non-intact meats and to assist in the validation of targeted interventions and the development of potential labeling and cooking requirements for such products.
Technical Abstract: Beef subprimals were inoculated on the lean side with about 3.5 or 5.5 log CFU/g of a five-strain mixture of rifampicin resistant (Rifr) Shiga toxin producing Escherichia coli O157:H7 (ECOH) and/or kanamycin resistant (Kanr) non-O157:H7 Shiga toxin producing E. coli (STEC) and then passed once through a mechanical blade-tenderizer with the lean side facing upwards. In each of two trials, ten core samples were removed from each of two tenderized subprimals and cut into six consecutive segments starting from the inoculated side: segments 1 to 4 comprised the top four cm and segments 5 and 6 comprised the deepest four cm. A total of ten cores were also obtained from two nontenderized (control) subprimals in each of two trials, but only segment 1 was sampled. The levels of ECOH and STEC recovered from segment 1 were ca. 6.0 and 5.3 log CFU/g for the control subprimals, respectively, whereas ca. 5.7 and 5.0 log CFU/g of ECOH and STEC were recovered from segment 1 of tenderized subprimals, respectively. However, both ECOH and STEC were recovered from all six segments of the cores obtained from tenderized subprimals, albeit at lower levels than found in segment 1, and both STEC and ECOH behaved similarly relative to translocation. As another component of this study, lean side inoculated (ca. 3.5 or 5.5 log CFU/g), single-pass tenderized subprimals were cut into 2.54 and 3.81 cm thick steaks that were subsequently cooked (3 steaks per treatment) on a commercial open-flame gas grill to internal temperatures of 48.9 deg, 54.4 deg, 60.0 deg, 65.6 deg, and 71.1 deg C. Regardless of temperature or thickness, we observed about a 2.0- to 4.1-log and 1.5- to 4.5-log CFU/g reduction in ECOH and STEC levels, respectively, following cooking. From a public health perspective, ECOH and STEC behaved similarly, in that cooking blade tenderized steaks on a commercial gas grill eliminated significant numbers of both pathogen types, albeit while allowing for the recovery of fortuitous survivors.