Analysis of RTE Test Results as a Function of Listeria monocytogenes (Lm) Sanitation Control Alternative

Introduction: Federal regulation 9CFR430 establishes four alternatives for controlling Lm for establishments producing Ready-to-Eat (RTE) products. Alternative (Alt) 1 uses both a post-lethality treatment (PLT) that reduces or eliminates microorganisms on the product as well as an antimicrobial agent or process (AMAP) that suppresses or limits the growth of Lm.  Alternatives 2a and 2b use either a PLT or an AMAP, respectively. Alternative 3 only uses sanitation measures.

Purpose: FSIS evaluated the effects of each alternative on percent positive rates using Lm RTE program data for product samples, food contact surface (FCS) samples and non-food contact environmental samples for years 2005–2012.

Methods: FSIS tested product samples for Lm using FSIS’s Microbiology Laboratory Guidebook. Results were compared to the interventions applied at the establishment.

Results: The analysis ranked the effectiveness of the different alternatives as follows: Alt1 > Alt2a ≈ Alt2b > Alt3 (overall percent positive rates were 0.21%, 0.3%, 0.27% and 0.42%, respectively). The results indicate that sanitation alone was less effective than some forms of intervention (PLT and/or AMAP) for controlling Lm contamination in both products and FCS. Statistically significant differences (P < 0.05) were observed between alternatives 2b and 3 for product and FCS samples, while the difference between environmental samples tested under the two alternatives approached statistical significance (P< 0.08). A smaller number of samples were collected and tested under alternatives 1 and 2a (less than 5% of all samples collected) compared to alternatives 2b and 3.

 Significance: The results suggest that PLT and/or AMAP are more effective than sanitation alone in controlling Lm.