A 500-base-pair DNA fragment of a presumptive jI-hemolysin gene of Listeria monocytogenes has been used to identify this organism by a modified colony hybridization technique. We have cloned this DNA fragment into M13 bacteriophage vectors and sequenced it by a dideoxynucleotide sequencing technique. From this sequencing information, several oligodeoxyribonucleotides were synthesized and used as synthetic probes to identify L. monocytogenes. The probes were specific for L. monocytogenes and did not react with any other Listeria strains in a colony hybridization assay. In particular, one of these probes (AD07) was used to detect L. monocytogenes in artificially contaminated raw-milk and soft-cheese samples.

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