ARS | Publication request: Assay to measure efficacy of dininfectants against Listeria monocytogenes biofilms

Submitted to: Association Official Analytical Chemists Annual Intrl Meeting & Exposition
Publication Type: Abstract
Publication Acceptance Date: July 24, 2008
Publication Date: September 24, 2008
Citation: Arnold, J.W., Kramer, S., Weiner, Z.A. 2008. Assay to measure efficacy of dininfectants against Listeria monocytogenes biofilms. Association Official Analytical Chemists Annual Intrl Meeting & Exposition. P-300, p.150.

Technical Abstract: Listeria monocytogenes is responsible for a 20 to 30% death rate in humans, and more food product recalls than any other pathogen in recent years. Many disinfectants have been tested against this pathogen. This study provides a method for testing and comparison of disinfectant product claims. Two products were compared for efficacy against L. monocytogenes in biofilms. A bioractor was used to grow L. monocytogenes biofilms on stainless steel coupons under flow conditions that were similar to wet food processing areas. An aerobic plate count was performed to assess the initial presence of the bacteria in the reactor as well as on the coupons after each 24 h period. A portion of the coupons were treated with each of the two products or left untreated, stained with crystal violet dye, extracted with ethanol, and measured for biofilm production by spectrophotometry. The presence of biofilm mass, before and after treatment, was confirmed by epifluorescent microscopy. The same coupons were stained using the bacterial stain 4;, 6-Diamidino-2-phenylindole dihydrochloride (DAPI), the epifluorescene observed, and the densitometric means for randomly selected fields per coupon were analyzed. The assay methods compared the disinfectants for killing and biofilm removal of L. monocytogenes biofilm. The result show taht the products were effective, with total kill and more than 90% biofilm removal by each product. Effective products could be of great use for sanitation in food and health areas to help reduce cases of listeriosis across the nation.