Comparison of Media and Procedures for the Isolation of Listeria monocytogenes from Ground Beef

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Abstract
Eight protocols for the isolation of Listeria monocytogenes from meat were used to compare the sensitivity of the Listeria enrichment broth of Donnelly and Baigent (DB) to that of a Listeria test broth (LTB) containing horse serum and Tween 80. In addition to L. monocytogenes, other Listeria spp. were isolated from the majority of lean ground beef samples purchased from 50 retail outlets. Nineteen samples were positive using DB broth while 16 were positive using LTB. This difference was not significant. Neither broth alone recovered all of the 29 positive samples. However, sensitivity was significantly improved when two of the three protocols were used in parallel. Of 2986 isolates tested for β-hemolysis in horse blood agar, 654 (21.9%) were positive.