TY - JOUR
T1 - Optimizing detection of heat-injured Listeria monocytogenes in pasteurized milk
AU - Teo, A. Y.L.
AU - Ziegler, G. R.
AU - Knabel, S. J.
PY - 2001
Y1 - 2001
N2 - Optimal conditions for the detection of heat-injured cells of Listeria monocytogenes in modified Pennsylvania State University (mPSU) broth were determined using a response surface design generated by a computer program, EChip. Different combinations of incubation temperatures and lithium, magnesium, and D-serine concentrations were evaluated to determine the optimum conditions for the detection of heat-injured L. monocytogenes in filter-sterilized whole milk inoculated with selected problematic background microflora. A concentration of 212 mM lithium chloride completely inhibited the growth of Enterococcus faecium while permitting recovery and detection of L. monocytogenes. A concentration of 15.8 mM MgSO4 was found to be optimum for the recovery and detection of L. monocytogenes. A concentration of 140.2 mM D-serine was found to completely inhibit the germination of Bacillus subtilis var. globii spores but not recovery and detection of L. monocytogenes. Under optimum concentrations of LiC1, MgSO4, and D-serine and in the absence of background microflora, the effect of incubation temperature on percentage detection was described by a second-order polynomial model, and 28°C was determined to be optimal. In the presence of background microflora, the effect of incubation temperature on percentage detection of heat-injured cells was described by a third-order polynomial model, and 30°C was found to be optimal. Optimizing the levels of highly specific and selective agents, nutrients, and incubation temperature in one recovery enrichment system dramatically increased the Listeria/background microflora ratio. This resulting medium, optimized PSU (oPSU) broth, greatly improved the detection of heat-injured and nonheat-injured L. monocytogenes by both conventional and molecular methods (Oxoid's Listeria Rapid Test, Gen-Probe's Accuprobe Listeria monocytogenes Culture Identification Test, and Qualicon's BAX for screening Listeria monocytogenes).
AB - Optimal conditions for the detection of heat-injured cells of Listeria monocytogenes in modified Pennsylvania State University (mPSU) broth were determined using a response surface design generated by a computer program, EChip. Different combinations of incubation temperatures and lithium, magnesium, and D-serine concentrations were evaluated to determine the optimum conditions for the detection of heat-injured L. monocytogenes in filter-sterilized whole milk inoculated with selected problematic background microflora. A concentration of 212 mM lithium chloride completely inhibited the growth of Enterococcus faecium while permitting recovery and detection of L. monocytogenes. A concentration of 15.8 mM MgSO4 was found to be optimum for the recovery and detection of L. monocytogenes. A concentration of 140.2 mM D-serine was found to completely inhibit the germination of Bacillus subtilis var. globii spores but not recovery and detection of L. monocytogenes. Under optimum concentrations of LiC1, MgSO4, and D-serine and in the absence of background microflora, the effect of incubation temperature on percentage detection was described by a second-order polynomial model, and 28°C was determined to be optimal. In the presence of background microflora, the effect of incubation temperature on percentage detection of heat-injured cells was described by a third-order polynomial model, and 30°C was found to be optimal. Optimizing the levels of highly specific and selective agents, nutrients, and incubation temperature in one recovery enrichment system dramatically increased the Listeria/background microflora ratio. This resulting medium, optimized PSU (oPSU) broth, greatly improved the detection of heat-injured and nonheat-injured L. monocytogenes by both conventional and molecular methods (Oxoid's Listeria Rapid Test, Gen-Probe's Accuprobe Listeria monocytogenes Culture Identification Test, and Qualicon's BAX for screening Listeria monocytogenes).
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U2 - 10.4315/0362-028X-64.7.1000
DO - 10.4315/0362-028X-64.7.1000
M3 - Article
C2 - 11456184
AN - SCOPUS:0034945931
SN - 0362-028X
VL - 64
SP - 1000
EP - 1011
JO - Journal of food protection
JF - Journal of food protection
IS - 7
ER -