The effect of commercial sanitizers on <i>Listeria monocytogenes</i> (planktonic and biofilm forms) experimentally inoculated materials commonly used during tree-fruit harvesting

This study compares the efficacy of commercially available sanitizers in reducing Listeria monocytogenes planktonic and biofilm form on surfaces commonly used during tree fruit harvesting. Planktonic L. monocytogenes cells were grown to create a bacterial lawn and inoculated on high-density polyethylene plastic, wood, or nylon. Biofilms were grown for 96 h in a Centers for Disease Control reactor on the same surfaces. Bacteria were exposed to free chlorine, peroxyacetic acid, silver-dihydrogen citrate, steam, and chlorine dioxide. In planktonic forms, peroxyacetic acid and silver-dihydrogen citrate, applied for 2 min resulted in ≥3-log reduction regardless surface type (P < 0.05). Steam and chlorine dioxide efficacy differed significantly by surface type. When applied to Listeria biofilms, steam, chlorine, peroxyacetic acid, and chlorine dioxide resulted in an overall significant difference compared to untreated coupons for all surfaces (P < 0.05). Silver-dihydrogen citrate significantly affected population on plastic (P < 0.05), but not on wood or nylon. For porous surfaces few treatments, such as peroxyacetic acid (for nylon) and chlorine dioxide (for wood), resulted in a ≥3 log reduction of both forms. Interactions between sanitizer, surfaces, and exposure time should be considered by tree fruit harvesting facilities when determining sanitation strategies to be implemented.