E. coli O157:H7 as an Indicator for the "Big 6" STECs

Recent USDA-FSIS rules have declared six new non-O157 STEC serogroups (O103, O111, O121, O145, O26 and O45) as adulterants in raw ground and non-intact beef products in addition to E. coli O157:H7. A need therefore arises to evaluate current intervention approaches to E. coli O157:H7 for efficacy against the non-O157 STEC serogroups. There has been much speculation that the use of current interventions will effectively reduce the non-O157 STECs in amounts equivalent to the reductions achieved with treatments directed against E. coli O157 on beef carcasses. However, data are needed to support these assumptions. Some preliminary data have indicated that the reduction of the pathogen loads on non-O157 STECs applied as a cocktail mixture to a carcass were SLIGHTLY less (0.2-0.3 log cycles less) than what we typically observe with E. coli O157. However, we previously were evaluating the reduction of six strains as opposed to one and we also did not directly compare reductions of the serogroup classifications of pathogens side by side. There is a need to evaluate the non-O157 STECs individually and not as a group (cocktail) to have strong data to support our hypothesis that the non-O157 STECs will be controlled in beef operations that are currently controlling E. coli O157. <P>We have identified the need to evaluate the "Big Six" non-O157 STECs in parallel, as opposed to a group, so as to obtain support that the non-O157 STECs will respond similarly to currently implemented intervention controls utilized effectively against E. coli O157 in beef operations. Our objectives were to (i) measure reductions of E. coli O157 and serogroups of non-O157 STEC in parallel by the application of hot water (HW, 180°F), lactic acid (LA, 5% ± 0.1) and acidified sodium chlorite (ASC, ≤1200 ppm) individually utilizing a simulated hot carcass brisket model and (ii) measure reductions of E. coli O157 and non-O157 STEC in parallel using the same interventions applied to chilled beef subprimals.