OLIGONUCLEOTIDE PROBES FOR MUTANS STREPTOCOCCI

Oligodeoxyribonucleotide probes complementary to hypervariable regions of the 16S ribosomal RNA were designed for specificity toward Streptococcus mutants and Streptococcus sobrinus. The probes were tested for specificity and sensitivity by hybridization with nucleic acid from over 100 mutans and non-mutans oral streptococci and other common oropharyngeal bacteria. Probes designated SM002 and SM010 were 100% sensitive and > 99% specific for S. mutants. Probe SSP001, designed to detect both S. mutants and S. sobrinus, was 88% sensitive and > 99% specific. The probes were able to detect nucleic acid extracted from 3 × 104-1 × 105 homologous bacteria. Sensitivity did not vary significantly with the growth state of the cells, except for diminished signals when using nucleic acid extracted from very old cultures. The probes correctly identified 72 S. mutans colonies isolated from 10 volunteer saliva samples, using sugar utilization patterns as a reference standard. Ten isolates resembling S. mutants by colony morphology but not by sugar utilization patterns were correctly distinguished from mutans streptocci by the probes. These results demonstrate that oligonucleotide probes can accurately identify S. mutans in saliva samples. © 1994 Academic Press, Limited.