Identification of Staphylococcus species by 16S-23S rDNA intergenic spacer PCR analysis

To investigate whether 165-235 rDNA (rDNA) spacer region length polymorphisms are suitable for the identification of Staphylococcus strains, the 165-235 rDNA intergenic spacer region lengths of 221 strains belonging to 31 species were studied by using a PCR-based method. Each species presented a specific 165-235 pattern made of 1-8 fragments ranging from 104 to 771 bp, with the exception of the species Staphylococcus warneri, Staphylococcus caprae and Staphylococcus piscifermentans, which presented larger or smaller fragments. Very few species showed more than one pattern, Staphylococcus saprophyticus subsp, saprophyticus and Staphylococcus aureus being the most heterogeneous species (five different patterns for eight strains). Five clinical strains that could not be identified at the species level by phenotypical tests were finally identified using this method. Discrimination between some species that showed close patterns (Staphylococcus cohnii/Staphylococcus chromogenes/Staphylococcus equorum, Staphylococcus aureus/Staphylococcus intermedius, Staphylococcus sciuri/Staphylococcus pasteuri/Staphylococcus gallinarum, Staphylococcus delphini/Staphylococcus felis, Staphylococcus vitulus/Staphylococcus auricularis) was further achieved after DraI digestion of the PCR products. Although it does not allow discrimination of subspecies, the use of 165-235 spacer region length data determined by PCR-mediated amplification is suitable for the identification of the 31 Staphylococcus species tested in this study. The method is rapid, easy and may be a useful tool for the identification of Staphylococcus species in the clinical microbiology laboratory.