Antimicrobial Efficacy of Radiant Catalytic Ionization against Shiga Toxin-producing Escherichia coli on Inoculated Beef

Introduction: Shiga Toxin-producing Escherichia coli (STEC), as a common foodborne pathogen, may cause severe human hemorrhagic colitis infection. The radiant catalytic ionization (RCI) technology utilizes a combination of UV light and low-level oxidizers such as ozone, hydroxyl radicals, and hydrogen peroxide to cause antimicrobial action, which can be considered as a potential intervention to effectively control pathogen contamination on carcasses and resulting beef products.

Purpose: The purpose of the project was to evaluate the effect of RCI on reduction of selected Escherichia coli (E. coli) O157:H7, non-O157 STEC O26, O45, O103, O111, O121, and O145 strains.

Methods: Pre-rigor beef flanks (168 pieces; 5 נ5 cm; n = 6) were inoculated with one of seven inoculum groups to a final concentration of 5 to 6 log CFU/cm². The inoculated beef flanks were exposed to RCI treatment for 0 s (untreated control), 15 s, 30 s, or 60 s at 4°C. Samples were surface plated on SDA and brain heart infusion agar (BHA) using a spiral-plater and analyzed for survivors then compared with the untreated controls.

Results: The counts of survivor strains from treated samples were significantly (P < 0.05) lower compared to that of untreated controls. The reductions of selected STEC strains by 15 s RCI exposure ranged from 0.65 – 1.24 log CFU/cm². When the exposure time was increased from 15 s to 60 s, with current RCI settings, additional 0.45, 0.38 and 0.76 CFU/cm² reductions were detected on E. coli O26, O45 and O157, respectively. However, the counts of survivors for E. coli O103, O111, O121, and O145 remained unchanged (P > 0.05) even though the exposure time was increased to 60s.

Significance: This research provides preliminary data for proof of concept for antimicrobial efficacy of RCI against STEC on the surface of fresh beef.