Comparison of three methods for identification of Streptococcus milleri group isolates to species level

A collection of 180 clinical isolates of Streptococcus milleri group were i dentified to species level using two phenotypic methods (a commercial syste m and the reference method based on differential phenotypic reactions) and a genotypic method (hybridisation of the 16S rRNA gene with species-specifi c probes) in order to evaluate the performance of the respective methods. A high level of agreement (80%) was observed between the results of the refe rence method and the genotypic method. The highest level of agree ment was found for the species Streptococcus anginosus (83%), a high level of agreem ent (76%) also being achieved for Streptococcus constellatus and Streptococ cus intermedius. The sensitivity of the commercial system compared to the g enotypic method was 76% overall, but it was low (57.5%) for Streptococcus i ntermedius. Twenty-five strains belonged to the recently described CI strai ns.