Controlling Attachment and Growth of Listeria monocytogenes in PVC Model Floor Drains Using a Peroxide Chemical, Chitosan-arginine or Heat

Introduction: Listeria monocytogenes enters a poultry further processing plant with raw product and colonizes the plant as a resident in floor drains.  We have shown that L. monocytogenes can escape floor drains, becoming airborne during wash down, creating potential for contamination of fully cooked product.  Limiting growth and attachment to drain surfaces may help prevent cross contamination.

Purpose: The objective of this study was to compare a synthetic hydrogen peroxide-based chemical proven to be effective in drain sanitizing to naturally derived chitosan-arginine or heat to prevent attachment of or destroy existing L. monocytogenes on the inner surface of model floor drains. 

Methods: L. monocytogenes was introduced to result in about 10⁹ planktonic and attached cells within untreated PVC model drain pipes.  Treatments (0.13% peroxide based sanitizer, 0.1% chitosan-arginine or 15s of hot water at 95 - 100°C) were applied immediately after inoculation, or after 24h incubation.  Following treatment, all pipes were incubated for an additional 24h; planktonic and attached cells were enumerated by plate count. 

Results: All treatments significantly (P < 0.05) lowered numbers of planktonic and attached cells recovered.  Chitosan-arginine resulted in a 6 log reduction when applied prior to incubation and a 3 log reduction after the inoculum had a chance to grow.  Both heat and peroxide significantly outperformed chitosan-arginine (8 to 9 log reduction) and were equally effective before and after incubation.  Heat was the only treatment which eliminated planktonic L. monocytogenes.

Significance: Based on these data, a processor can choose between a natural solution, a chemical solution or a physical treatment to combat drain contamination.   Applied at the most efficacious time, any of these techniques may lessen the potential for L. monocytogenes to remain as a long term resident in processing plant floor drains.