Purpose: To quantify reductions of each non-O157 STEC serogroup achieved by lactic acid (LA), hot water (HW) and acidified sodium chlorite (ASC) simultaneously with E. coli O157:H7 on chilled beef subprimals.
Methods: Chilled subprimals (n = 86) are utilized and four subprimals are randomly assigned to each serogroup and antimicrobial intervention (2 control + 2 interventions). For each serogroup and intervention, four subprimals were inoculated by submersion (1 minute) into a 3-strain cocktail, subjected to a 30 minute attachment period and placed in a chad cabinet for intervention application. Sample swabs were collected both pre- and post-intervention and plated onto MacConkey agar.
Results: When treated with LA, O157 showed 0.65-log reduction while the non- O157 STEC serogroups showed 0.24 to 0.58-log reduction except O103, which showed no numerical reduction. STEC O157 when treated with HW and ASC exhibited 0.61 and 0.44-log reductions, respectively. HW and ASC achieved reductions in all the six non-O157 serogroups ranging from 0.07 to 0.43 and 0.26 to 0.83-log reductions, respectively. When treated with LA, non-O157 STEC serogroup reductions were not statistically different from E. coli O157 reductions, with the exception of serogroup O103 (P = 0.011), but are all significantly different from E. coli O157 reductions, with the exception of O121, when treated with HW. Reductions observed for non-O157 STEC serogroups treated with ASC were not significantly different from E. coli O157.
Significance: Although not universal among all serogroups and interventions (i.e., O103 and LA), E. coli O157 may act as an effective indicator for detecting reductions among the 6 non-O157 STEC serogroups.