Title: Effect of chemical sanitizers with and without ultrasonication on Listeria monocytogenes as a biofilm within polyvinyl chloride drain pipes Authors
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 17, 2007
Publication Date: January 1, 2008
Citation: Berrang, M.E., Frank, J.F., Meinersmann, R.J. 2008. Effect of chemical sanitizers with and without ultrasonication on Listeria monocytogenes as a biofilm within polyvinyl chloride drain pipes. Journal of Food Protection. 7(1):66-69. Interpretive Summary: Listeria monocytogenes is a human pathogen that can colonize floor drains in commercial chicken cooking plants. Such contamination can cause cross contamination of fully cooked ready-to-eat chicken meat resulting in an unsafe product. Cells of L. monocytogenes that are attached to the inner surface of drain pipes as part of a biofilm can be protected from the sanitizers used to clean floors and drains. Using a model drain system, we tested the use of ultra-sound treatment as a means to break up drain biofilms allowing sanitizers to make direct contact with L. monocytogenes. Chemical sanitizers (chlorine, peroxide or quaternary ammonium) were applied to model drain pipes with and without a 30s ultra-sonication treatment. All sanitizers were effective in decreasing the numbers of L. monocytogenes not directly associated with a biofilm, but were less effective against attached cells. The peroxide based sanitizer was most effective in decreasing the numbers of L. monocytogenes attached to the inner surface of the drain. Although treatment with ultrasound did not improve the performance of the peroxide based sanitizer, it did improve the effectiveness of the other two chemicals tested. The chlorine based sanitizer, when used in concert with ultrasound, was as effective as the peroxide based sanitizer; the quaternary ammonium sanitizer was slightly less effective. These results indicate that use of a peroxide based sanitizer alone can be very effective against biofilm L. monocytogenes in drain pipes. However, the addition of ultra-sonication can improve the effectiveness of chlorine or quaternary ammonium sanitizers. This information is useful to poultry further processors in their effort to find new procedures for sanitizing floor drains.
Technical Abstract: As part of a biofilm in a floor drain, L. monocytogenes is exceedingly difficult to eradicate with standard sanitizing protocols. The objective of these studies was to test the use of ultra-sonication to break up biofilm architecture allowing chemical sanitizers to contact cells directly. L. monocytogenes biofilms were created in model PVC drain pipes. Chemical sanitizers (quaternary ammonium, peroxide or chlorine) were applied to the drain pipes with and without a 30s ultra-sonication treatment. Controls using sterile water were included for comparison. L. monocytogenes cells were enumerated from the liquid in the drain and the inside wall surface of the pipe. All chemicals lowered numbers of planktonic cells from 6.6 log cfu/ml in the water control to <100 cfu/ml. Attached cells were also affected by the chemical sanitizers. Approximately 6.0 log cfu were detected per cm2 of the inner wall surface of water control pipes; ultra-sonication did not lower the numbers of attached cells in the water control pipes. With or without ultra-sonication, the peroxide based sanitizer was effective to lessen the numbers of attached L. monocytogenes resulting in approximately 2.0 log cfu/cm2. Both the chlorine and quaternary ammonium based sanitizers lowered the number of attached L. monocytogenes to a lesser degree resulting in 4.2 - 4.4 log cfu/cm2. However, addition of ultra-sonication improved the performance of both these sanitizers causing a further reduction to 3.1 and 2.9 cfu/cm2 for quaternary ammonium and chlorine based chemicals respectively. These results indicate that a peroxide based sanitizer alone can be very effective against biofilm L. monocytogenes in drain pipes while addition of ultra-sonication can improve the effectiveness of chlorine or quaternary ammonium sanitizers.