Rapid detection and identification of Streptococcus macedonicus by species-specific PCR and DNA hybridisation

The aim of this study was to develop a simple and specific method for the rapid detection and identification of Streptococcus macedonicus. The method was based on polymerase chain reaction (PCR) using species-specific primers derived from the 16S rRNA gene. Specific identification was proven on seven S. macedonicus strains, while 16 strains belonging to different lactic acid bacteria species were tested negative. The PCR assay was capable of detecting 100 pg of S. macedonicus DNA, and it was also efficient on single colonies of the bacterium. Furthermore, the same bacterial strains were used for the specificity evaluation of a S. macedonicus species-specific probe. Neither species-specific PCR nor DNA hybridisation experiments could differentiate Streptococcus waius from S. macedonicus, due to the identity of the 16S rRNA gene of the two species, indicating high phylogenetical relatedness. This was further confirmed by the comparative sequence analysis of the 16S-23S rRNA intergenic regions. It was thus clearly demonstrated that S. waius, recently described as a novel Streptococcus species, is phylogenetically identical to S. macedonicus.