Evaluation of Potential for Translocation of Listeria monocytogenes from Floor Drains to Food Contact Surfaces in the Surrounding Environment Using Listeria innocua as a Surrogate

Floor drains in processing environments harbor Listeria spp. due to continuous presence of humidity and organic substrates. Cleaning and washing activities in food-processing facilities can translocate the bacterial cells from the drain to the surrounding environment, thus contaminating food products still in production. This study evaluated the potential for translocation of Listeria monocytogenes from drains to food contact surfaces in the surrounding environment using Listeria innocua as a surrogate. A 7 × 7 × 8-foot polycarbonate flexi-glass chamber with a 10-inch-diameter drain mounted on an aluminum cabinet was used. Stainless steel coupons (6.4 × 1.9 × 0.1 cm, 12 per height) were hung at 1, 3, and 5 feet inside the chamber. Four treatment sets; non-inoculated, non-treated; non-inoculated, treated; inoculated, treated; inoculated non-treated; and two subtreatments of 8 h and 48 h were performed. For the inoculated sets, meat slurry (10 g of ground beef in 900 mL water) and a four-strain cocktail of Listeria innocua at 7 8 log CFU/mL were used. For the treated sets, in addition, a commercial cleaner and sanitizer was applied. The drain was cleaned using a pressure hose (40 50 psi) after 8 h and 48 h. Coupons were then removed and enriched in listeria enrichment broth to establish if any cell translocated from the drain onto the stainless steel coupons via aerosols generated during washing. Confirmation was done using VIP Listeria rapid test kits. Results indicated translocation at all three heights ranging from 2% 25%. Significantly higher translocation (p < 0.05) was found at 1 foot (up to 25%), followed by 3 feet (up to 11%) and 5 feet (up to 2.7%). This research indicated that translocation of Listeria spp. from drains to food contact surfaces does occur and increases with increased proximity to the drain.