USE OF RESTRICTION FRAGMENT POLYMORPHISM ANALYSIS OF RIBOSOMAL-RNA GENES TO ASSIGN SPECIES TO UNKNOWN CLINICAL ISOLATES OF ORAL VIRIDANS STREPTOCOCCI

This study evaluated restriction fragment length polymorphisms of rRNA genes (ribotyping) for genotypic identification of 53 oral isolates c lassified as ''Streptococcus sanguis'' by colony morphology. Isolates were from 8-h buccal plaque on lower first permanent molars of 20 subj ects. DNA was digested with AatII and hybridized with digoxygenin-labe led cDNA of Escherichia coli 16S and 23S rRNA. Strains were ribotyped again with AlwNI or PvuII on the basis of the presence or absence of a 2,290-bp AatII band. Band patterns were compared with reference ribot ypes for Streptococcus gordonii, Streptococcus sanguis, Streptococcus crista, Streptococcus oralis, Streptococcus mitis, and Streptococcus p arasanguis strains. Forty-eight isolates could be assigned to a specie s (22 S. sanguis, 14 S. oralis, 12 S. gordonii). Multiple species were seen in 14 subjects; multiple strains of the same species occurred in 11 subjects. Our findings suggest that ribotyping can be used for gen otypic identification of S. sanguis, S. oralis, and S. gordonii isolat es.