Characterization of Listeria monocytogenes isolates by Southern blot hybridization.

A synthetic deoxyribonucleotide probe for virulent Listeria monocytogenes, designated ADO7, was evaluated for its ability to identify restriction fragments of L. monocytogenes with nucleic acid sequences homologous with the beta-hemolysin gene by Southern blot hybridization of clinical and food isolates. The synthetic probe hybridized with three restriction fragments (approximately 1.1, 0.86, and 0.76 kb) of the serotype 1/2A isolates. Southern blot hybridization of the serogroup 4B isolates indicated that the nucleic acid sequences homologous with the beta-hemolysin gene probe were limited to a single restriction fragment of approximately 1 kb.