Physiological characterization and identification of Listeria species.

A total of 136 strains of the genus Listeria were physiologically characterized using 329 miniaturized tests. Overall similarities of all strains were determined by numerical taxonomic techniques using the UPGMA algorithm and the SSM and SJ coefficients. A total of 10 clusters (2 or more strains) and 1 single-member cluster were defined at the 95.1 to 95.8% similarity levels (SSM). The same clusters were found at the 76.8% to 77.8% similarity levels (SJ). Strains of L. seeligeri, L. welshimeri, L. ivanovii, L. murrayi and L. grayi were found in separate clusters and formed homogeneous taxospecies. In contrast, strains of L. monocytogenes and L. innocua formed five heterogeneous clusters and one single-member cluster. For differentiation of the phena the following tests are useful: utilization of D-xylose, D-xylitol, D-ribose, D-galactose, alpha-methyl-D-mannoside, methyl-alpha-D-glucopyranoside, inulin and L-rhamnose, acid production from D-glucuronate, alpha-D-galacturonate, alpha-methyl-D-mannoside, methyl-alpha-D-glucopyranoside, D-xylose, L-lyxose, D-sucrose, alpha-D-melizitose, D-tagatose, and D-ribose and hydrolysis of pNP-alpha-D-glucopyranoside, pNP-alpha-D-mannopyranoside and 2-deoxythymidine-5'-pNP-phosphate. Independent of the assignment of some strains of L. monocytogenes and L. innocua to the same cluster, members of these species can be separated by hydrolysis of D-alanine-p-nitroanilide.