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Table 3 Number of positive test portions out of 20 test portions generated for D/E, Letheen, and HiCap neutralizing broths using an inoculation level of ~ 800 CFU/square Lm followed by an application of 400 ppm of quat and an inoculation level of ~ 3000 CFU/square Lm followed by an application of 8000 ppm of quat before sampling. Neutralizing broths were stored at 4 °C before use

From: Comparison of three neutralizing broths for environmental sampling of low levels of Listeria monocytogenes desiccated on stainless steel surfaces and exposed to quaternary ammonium compounds

Initial inoculation level and quat concentration Storage condition between collection and analysis Number of positive test portions collected using each brotha
D/E Letheen HiCap
~ 800 CFU/square of Lm and 400 ppm of quat 2 h at RT (p = 0.44) 18 15 15
24 h at 4 °C (p = 0.06) 13 a 19 b 18 ab
72 h at 4 °C (p = 0.15) 14 19 16
~ 3000 CFU/square of Lm and 8000 ppm of quat 2 h at RT (p = 0.0002) 10 a 1 b* 13 a
24 h at 4 °C (p = 0.002) 12 a 2 b* 11 a
72 h at 4 °C (p = 0.0008) 11 a 2 b* 13 a
  1. aExtended Fisher’s exact tests for each row among different enrichment broths, and p values are listed in the parenthesis after each storage condition. When p was less than 0.1, pairwise comparisons were performed; results sharing the same letter were not statistically different (p > 0.05) and * indicates p < 0.01 between different letters. p values of pairwise comparisons are not listed