IDENTIFICATION OF STREPTOCOCCI TO SPECIES LEVEL BY SEQUENCING THE GENE ENCODING THE MANGANESE-DEPENDENT SUPEROXIDE-DISMUTASE

We have used a PCR assay based on the use of degenerate primers in ord er to characterize an internal fragment (sodA(int)) representing appro ximately 85% of the genes encoding the manganese-dependent superoxide dismutase in various streptococcal type strains (S. acidominimus, S. a galactiae, S. alactolyticus, S. anginosus, S. bovis, S. constellatus, S. canis, S. cricetus, S. downei, S. dysgalactiae, S. equi subsp. equi , S. equi subsp. zooepidemicus, S. equinus, S. gordonii, S. iniae, S. intermedius, S. mitis, S. mutans, S. oralis, S. parasanguis, S. pneumo niae, S. porcinus, S. pyogenes, S. salivarius, S. sanguis, S. sobrinus , S. suis, S. thermophilus, and S. vestibularis). Phylogenetic analysi s of these sodA(int) fragments yields an evolutionary tree having a to pology similar to that of the tree constructed,vith the 16S rRNA seque nces. We have shown that clinical isolates could be identified by dete rmining the positions of their sodA(int) fragments on the phylogenetic tree of the sodA(int) fragments of the type species. We propose this method for the characterization of strains that cannot be assigned to a species on the basis of their conventional phenotypic reactions.