Comparative recovery of Listeria spp. From dairy environmental surfaces using 3M™ and World Bioproducts© environmental swabs with standard enrichment and enumeration methods

Preventing Listeria contamination of artisan cheeses requires routine and effective environmental monitoring of product contact surfaces within the production environment. Consideration of the efficacy of environmental monitoring methods is essential when testing for the presence of Listeria spp. within the processing environment as a way to control the risk of cheese contamination. Four environmental surfaces (dairy brick, stainless steel, plastic, and wood; n = 27/surface type at high concentrations; n = 405/surface type at low concentrations) were inoculated with L. innocua (expressing Green Fluorescent Protein), L. monocytogenes. (L.m.), ATTC® 19115 and L.m. 1042B, at high (106–107 CFU/cm2) and low (0.01–1 CFU/cm2) target concentrations. Inoculated surfaces were swabbed with World Bioproducts© EZ Reach™ environmental swabs with HiCap (WBHC) and Dey-Engley (WBDE) neutralizing broths, and 3M™ environmental swabs (3M™) with Dey-Engley neutralizing broth. 3M™ Listeria Environmental Plate and Aerobic Plate Count Petrifilm™ enumeration methods and FDA, modified FDA, MOPS-BLEB, and modified USDA enrichment methods were used to compare sensitivity of recovery between environmental swabs. When applied at low concentrations, 3M™, WBDE, and WBHC swabs recovered Listeria spp. from 90.9%, 88.4% and 83.2% of plastic, stainless steel, and dairy brick surfaces, respectively, but only 65.7% of wooden surfaces; recovering 14.8%, 77%, and 96.3% at 0.01, 0.1, and 1 CFU/cm2, respectively (p