Affiliation:
1. Department of Epidemiology and Preventive Medicine, School of Veterinary Medicine, University of California, Davis. CA 95616
Abstract
Three selective enrichment broths (FDA, University of Vermont and Dominguez Rodriguez) and lithium chloride-phenylethanol-moxolactam (LPM) agar, modified McBride (MMA) agar, Listeria selective agar (LSAM of Dominguez-Rodriguez), and Brain Heart Infusion (BHI) agar (as reference) were evaluated for their suitability to support the growth of six different species/strains of Listeria (Listeria monocytogenes Scott A, L. monocytogenes V7, L. monocytogenes VPH-1, Listeria innocua, Listeria seeligeri, and Listeria ivanovii). All Listeria strains grew faster and yielded a higher number of cells in FDA enrichment broth. Based on MPN studies, 1 to 2.1 cells of L. monocytogenes and L. innocua were needed for visible colony formation, on all three selective and BHI agars after 48 h incubation of 37°C. The LPM agar was more inhibitory for L. seeligeri and L. ivanovii requiring 9.6 and 917 cells, respectively, as compared to 1 to 2.7 cells for the other agars. The effectiveness of a particular combination among the selective enrichment broths and agars for recovering L. monocytogenes Scott A from inoculated cheese and meat samples was quantitated. Any enrichment broth combined with plating on LPM or LSAM agar gave 100% Listeria recovery as compared to 50 to 67% for plating on MMA agar. Both LPM and LSAM agars have also shown a superior performance to MMA agar in the recovery of naturally occurring Listeria from soft cheese and raw meat. The use of a secondary broth enrichment step improved the recovery of Listeria spp. from meat samples.
Publisher
International Association for Food Protection
Subject
Microbiology,Food Science
Cited by
14 articles.
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