Identification of classical Propionibacterium species using 16S rDNA-restriction fragment length polymorphisms

The phenotypic identification of the classical propionibacteria is essentially still problematic and alternative techniques for the identification of the various species are required. A rapid and sensitive technique for the routine identification of the classical propionibacteria, based on the amplification of 16S rRNA genes using the polymerase chain reaction and the subsequent restriction endonuclease digestion of the PCR products, was previously described. Although this technique enabled differentiation between the various classical species examined it was only evaluated on a limited number of type and reference strains. During this study, the taxonomic relationship between 135 Propionibacterium strains from diverse ecological niches, representing four classical species was investigated using this PCR/RFLP technique. Visual differentiation between the classical Propionibacterium was possible after restriction endonuclease digestion of the PCR products obtained using primers 16sP1-16sP4 and 16sP3-16sP4 with the restriction endonucleases HaeIII, AluI and HpaIII, respectively. With the exception of strains independently identified as "P. rubrum" and "P. sanguineum", the results of this study confirm the consolidation of the "old" species into the various classical species as they currently exist. It was therefore concluded that the PCR/RFLP protocol is suitable for the rapid and routine identification of the classical propionibacteria.