Genetic diversity of Streptococcus thermophilus strains isolated from Italian traditional cheeses

Randomly amplified polymorphic DNA (RAPD)-PCR was applied to the identification and typing of 218 Streptococcus thermophilus isolates from four Italian protected designation of origin type of cheeses. The pronounced differences among the RAPD-PCR profiles obtained with the primers M13 and D11344 revealed the presence of a significant genetic heterogeneity inside the species S. thermophilus. Randomly amplified polymorphic DNA-PCR also allowed to discriminate part of the S. thermophilus isolates according to the cheese origin. Finally, isolates showing RAPD-PCR profiles very similar to the profiles of two Streptococcus macedonicus reference strains were detected, suggesting the presence of these streptococci also in Italian cheeses.