Spray Intervention Treatments and Cooking to reduce Escherichia coli O157:H7 and Non-O157 STECs on the Surface of Beef Subprimals, and within Needle-Tenderized Steaks

Introduction:  In recent years, the reported cases of illness caused by non-O157 Shiga Toxin-Producing Escherichia coli (STEC) have been rising, becoming a threat to public health, and leading to six non-O157 STECs to be declared as adulterants in ground beef by the USDA-FSIS. 

Purpose:  The objectives were to (i) compare the difference of antimicrobial spray treatments on the reduction of E. coli O157:H7 and non-O157 STECs on beef subprimals after 14 days during vacuumed, refrigerated storage, and to (ii) evaluate the effect of cooking to reduce E. coli O157:H7 and non-O157 STECs (Serotypes O26, O103, O111 and O145) in needle tenderized meat.

Methods:   USDA Select beef strip loins were inoculated with 10⁶ or 10² cfu/cm² cocktails of either E. coli O157:H7 (study 1) or non-O157 STECs (study 2) before spray treatments [water, 5% lactic acid (LA), 0.02% hypobromous acid (HB2), or 0.02% peroxyacetic acid] and vacuumed storage. On day 14, each subprimal was needle tenderized, cut into three 2.54 cm-thick steaks, and assigned to uncooked, 50°C, and 70°C internal temperatures. Swab samples (50 cm²) were collected from the subprimal surface after inoculation, five minutes after spray treatment, and before tenderization. An additional swab was obtained from the surface of one raw steak per treatment. Internal meat samples (10 grams) were also taken from all uncooked and cooked steaks.

Results:  After 14 days, E. coli O157:H7 was reduced by LA with 2.3 log₁₀ cfu/50 cm², while non-O157 STECs was reduced by HB2 with 1.0 log₁₀ cfu/50 cm². Regardless of spray treatment, lower cooking temperature did not significantly reduce the non-O157 STECs, with serotype O103 being the most prevalent strain found in cooked samples. Cooking to 70°C was effective in controlling O157:H7 to non-detectable numbers.

Significance:  The results of this study provide the information about non-O157 STEC that can be used to develop more efficient and effective subprimal intervention strategies aimed to prevent STEC in non-intact meat products.