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

Abstract

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/cm2) with a five-strain composite of L. monocytogenes in ham homogenate and incubated at 24°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/cm2. 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.