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United States Department of Agriculture

Agricultural Research Service

Research Project: Microbial Ecology of Human Pathogens Relative to Poultry Processing

Location: Bacterial Epidemiology and Antimicrobial Resistance

Title: Controlling attachment and growth of Listeria monocytogenes in PVC model floor drains using a peroxide chemical, chitosan-arginine or heat.

Authors
item Berrang, Mark
item Hofacre, Charles -
item Frank, Joseph -

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 13, 2014
Publication Date: N/A

Interpretive Summary: Listeria monocytogenes is a human pathogen that can be present in commercial chicken cooking plants. L. monocytogenes enters the plant with incoming raw meat and eventually makes its way to floor drains where it can become a long term resident. This sets the stage for potential cross contamination of other areas of the plant and even fully cooked ready-to-eat poultry meat. Poultry processors need effective means to sanitize floor drains and other surfaces to lessen the presence of human pathogens such as L. monocytogenes. Since bacteria can develop tolerance to sanitizers, it is recommended to rotate treatments to maintain effectiveness. We tested three methods to sanitize floor drains including a peroxide/peroxyacetic acid (PPA) chemical, naturally derived chitosan-arginine and 95oC heat treatment for 15 s. Model floor drains were constructed and inoculated with L. monocytogenes such that some bacterial cells remained free swimming in the liquid and some became attached to the inner wall of the drain pipe. Individual treatments were applied either before or after the bacteria had a chance to reproduce in the model drain. Numbers of L. monocytogenes in the liquid and attached to the pipe were determined and compared to those found in untreated control pipes. All treatments lessened the numbers of free swimming L. monocytogenes, heat and PPA were the most effective; heat eliminated all detectable free swimming L. monocytogenes. Attached bacteria were somewhat more resistant but still all treatments were effective if applied before the bacteria could reproduce. Poultry processors can use this information in considering effective treatments to include in a rotation for drain sanitization.

Technical Abstract: Listeria monocytogenes can colonize a poultry processing or further processing plant as a resident in floor drains. Limiting growth and attachment to drain surfaces may help lessen the potential for cross contamination of product. The objective of this study was to compare a synthetic hydrogen peroxide/peroxyacetic acid 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. 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 15 s of hot water at 95 - 100oC) were applied immediately after inoculation, or after 24 h incubation. Following treatment, all pipes were incubated for an additional 24 h; planktonic and attached cells were enumerated by plate count. All treatments significantly (P < 0.05) lowered numbers of planktonic and attached cells recovered. Chitosan-arginine resulted in approximately a 6 log reduction in planktonic cells 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 detectable planktonic L. monocytogenes. All treatments were less effective against attached cells. Chitosan-arginine provided about a 4.5 log decrease in attached cells when applied before incubation and no significant decrease when applied after growth. Like with planktonic cells, peroxide/peroxyacetic acid and heat were equally effective before or after incubation causing decreases ranging from 7 to 8.5 log attached L. monocytogenes. 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.

Last Modified: 10/23/2014
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