Rapid and accurate species-level identification of coagulase-negative staphylococci by using the sodA gene as a target

Simple PCR and sequencing assays that utilize a single pair of degenerate p rimers were used to characterize a 429-bp-long DNA fragment internal (sodA( int)) to the sodA gene encoding the manganese-dependent superoxide dismutas e in 40 coagulase-negative staphylococcal (CNS) type strains. The topology of the phylogenetic tree obtained was in general agreement with that which was inferred from an analysis of their 16S rRNA or hsp60 gene sequences. Se quence analysis revealed that the staphylococcal sodA genes exhibit a highe r divergence than does the corresponding 16S ribosomal DNA. These results c onfirm that the sodA gene constitutes a highly discriminative target sequen ce for differentiating closely related bacterial species. Clinical isolates that could not be identified at the species level by phenotypical tests we re identified by use of this database. These results demonstrate the useful ness of this method for rapid and accurate species identification of CNS is olates, although it does not allow discrimination of subspecies. The sodA s equence polymorphisms observed with staphylococcal species offer good oppor tunities for the development of assays based on DNA chip technologies.