Sequencing of the Ribosomal Intergenic Spacer Region for Strain Identification of Porphyromonas gingivalis

The ribosomal intergenic spacer regions (ISRs) of 19 laboratory strains and 30 clinical samples of Porphyromonas gingivalis were amplified by PCR and sequenced to provide a strain identifier. The ISR is a variable region of DNA located between the conserved 16S and 23S rRNA genes. This makes it an ideal locus for differentiation of strains within a species: primers specific for the conserved flanking genes were used to amplify the ISR, which was then sequenced to identify the strain. We have constructed a P. gingivalis ISR sequence database to facilitate strain identification. ISR sequence analysis provides a strain identifier that can be easily reproduced among laboratories and catalogued for unambiguous comparison.