Purpose: To measure reductions of each non-O157 STEC serogroup included as an adulterant by applying lactic acid (LA; 5±0.2%), hot water (HW; 180 ±5° F) and acidified sodium chlorite (ASC; ≤1100 PPM) in parallel with E. coli O157:H7 in a hot carcass model (Brisket).
Methods: Briskets (n=14) were heated to 37°C, cut into halves and four brisket halves randomly assigned to each of seven serogroups (O157:H7, O26, O121, O45, O145, O111, O103). Four per each serogroup, brisket halves were inoculated by submersion into a 3-strain inoculum cocktail for 1 minute, allowed 30-minute bacterial attachment time, followed by simultaneous application of antimicrobial interventions (LA, HW and ASC). Pre-intervention and post-intervention swabs were obtained and plated onto MacConkey agar.
Results: Lactic acid significantly reduced the non-O157 STECs and the reductions are not statistically different compared to E. coli O157:H7, with the exception of STEC O111 (P = 0.049). When treated with HW, a 0.57-log reduction of E. coli O157 was achieved, which is not statistically different from serogroups O26, O121, O145, and O45. This study showed a log reduction of 0.63 for STEC O157 when treated with acidified sodium chlorite, which is significantly not different from serogroups O26, O121, O145, and O45.
Significance: These data indicate E. coli O157 is an effective indicator of intervention efficacy for the non-O157 STEC serogroups O26, O121, O145, and O45 and O103 when 5% LA is utilized, but may not be justified for serogroups O111 and O103 when HW or ASC are utilized.