ARS | Publication request: Translocation of Shiga-toxin producting cells of Escherichia coli in chemically-injected beef subprimals

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 11, 2010
Publication Date: N/A

Technical Abstract: Introduction: Relatively little information is available regarding the translocation of Escherichia coli O157:H7 (ECOH) and non-O157:H7 verocytotoxigenic E. coli (STEC) into beef subprimals following chemical tenderization. Purpose: Quantify translocation of ECOH or STEC from the surface into the interior of beef subprimals following tenderization by chemical injection. Methods: Beef subprimals were inoculated on the lean side with ca. 6.6 log CFU/g of a five-strain cocktail of rifampicin resistant ECOH or kanamycin resistant STEC and then passed once through an automatic brine-injector tenderizer with the lean side facing upwards. Brine solutions were as follows: i) 3.3% (w/v) of sodium tripolyphosphate and 3.3% (w/v) of sodium chloride (Lac-) or ii) 3.3% of sodium tripolyphosphate, 3.3% (w/v) of sodium chloride, and 25% (v/v) of a 60% potassium lactate-sodium diacetate syrup (Lac+). Brine was injected into subprimals to a target level of 9.1 +/- 0.8% over fresh weight. Six core samples were removed from each subprimal 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. Results: For samples that were injected with Lac- and Lac+ brine, levels of ECOH recovered from segment 1 were ca. 6.5 and 6.2 log CFU/g, respectively, whereas levels of STEC recovered from segment 1, were ca. 6.3 and 6.0 log CFU/g, respectively. Regardless of brine formulation, the percentage of ECOH and STEC recovered from segment 2 for brine-injected subprimals were 5- to 65-fold lower than levels recovered from segment 1. It was possible to recover ECOH or STEC from all six segments of all cores tested. Significance: These results validate that chemical tenderization transfers ECOH and STEC throughout the interior of beef subprimals. However, appreciably more cells were transferred to the topmost 1 cm compared to the deeper segments.