Levels Inoculation (CFU/surface) Replicates ┬áTEST (PDX-LIB Labor Savor) REFERENCE (USDA) Chi Squared Value
Presumptive Positives Confirmed False negatives Confirmed positives
Listeria innocua on ceramic tile -Ctrl 0 5 0 0 0 0 NA
Medium 4669 46688 20 19 19 0 6 15.36
High 20 20 20 0 19 0
Listeria ivanovii on stainless steel -Ctrl 0 5 0 0 0 0 NA
Medium 1175000 11750000 20 20 20 0 5 20.91
High 20 19 19 0 7 13.3
Listeria welshmeri on plastic -Ctrl 0 5 0 0 0 0 NA
Low 1506 150563 20 15 15 0 17 1.41
High 20 20 20 0 19 0
Listeria monocytogenes in10xE.colion sealed concrete -Ctrl 0 5 0 0 0 0 NA
Medium 715 7156 20 8 9 1 0 7.66
  High 20 14 15 1 3 10.23
Table 1: Summary of methods comparison at 48 hours incubation [12].