Rapid identification of Streptococcus thermophilus by primer-specific PCR amplification based on its lacZ gene

A method is presented allowing rapid and accurate identification of Streptococcus thermophilus by a primer-specific PCR-technique based on its lacZ gene sequence. For subsequent confirmation of the PCR-product (968 bp in length), the assay can additionally be combined with a hybridization step involving a S. thermophilus specific oligonucleotide probe (Lick and Teuber, 1992, System, Appl. Microbiol. 15, 456-459) hybridizing to the amplified sequence. The PCR-assay can be applied for rapid detection of S. thermophilus in fermented milk products like yoghurt. Nonspecific amplification was not observed with DNA's from a number of closely related species and a number of lactic acid bacteria which are used in combination with S. thermophilus for the manufacture of dairy products. This assay, therefore, may be applied for fast species-specific identification of S. thermophilus with no further need for hybridization.