Efficacy of Sanitizing Agents against Listeria monocytogenes Biofilms on High-Density Polyethylene Cutting Board Surfaces

This study compared the effectiveness of 10 commercially available sanitizers against Listeria monocytogenes biofilms on high-density polyethylene cutting boards. Smooth and rough surface high-density polyethylene coupons (2 by 5 cm) were inoculated (approximately 6 log CFU/cm(2)) with a five-strain composite of L. monocytogenes in ham homogenate and incubated at 24 degrees C and >= 90% relative humidity for up to 21 days. The coupons were subjected to repeated 24-h cycles simulating use and cleaning in the home. Each day, 0.3 ml of a 10-fold-diluted tryptic soy broth containing 0.6% yeast extract was added to each coupon (simulating exposure to nutrients during food preparation), and 8 h later each coupon was rinsed with sterile distilled water. Coupons were subjected to sanitizer treatments on days 0, 0.25, 7, 14, and 21. Eight quaternary ammonium compound (QAC)-based sanitizers, one of lactic acid-based sanitizer, and one sodium hypochlorite-based sanitizer were applied to individual coupons according to the manufacturers' instructions. Coupons were analyzed for L. monocytogenes (PALCAM agar) and total bacteria (tryptic soy agar with 0.6% yeast extract). At 0 and 0.25 days, nine of the sanitizers (all except for QAC-based sanitizer 10) had reduced L. monocytogenes to <0.60 log CFU/cm(2). For >= 7-day-old biofilms, the lactic acid-based sanitizer (pH 3.03) was the most effective, and the QAC-based sanitizers were more effective when at pH 10.42 to 11.46 than at pH 6.24 to 8.70. Sanitizer efficacies were greater (P < 0.05) against younger (7 days) than older (21 days) biofilms on smooth surfaces. For 7- and 14-day-old biofilms, sanitizer efficacies were higher (P < 0.05) on smooth than on rough surfaces.