Defferentiation of Streptococcus sobrinus from Streptococcus mutans and Discrimination of Mutans Streptococci by Genetic Engineering Techniques.

The aim of the present study was to differentiate S. sobrinus from S. mutans and to determine the species of mutans streptococci by PCR and DNA fingerprinting.The ftf primer was designed according to the sequence data of the regions containing the active site of FTF from S. mutans GS-5. The forward primer of gtf primer 1 was designed according to the base sequence coding for a common amino acid (DNSNPVV) which was found near the active site of GTF from S. mutans, S. sobrinus, and S. downei. The forward primer of gtf primer 2 was designed according to the base sequence coding for a common amino acid (EGFSNFQ) which was found by searching the GTF sequence data from S. mutans, S. sobrinus, S. downei and S. salivarius. The reverse primer of gtf primer 1 and gtf primer 2 was designed according to the base sequence coding for a common amino acid of the glucan binding domain of the gtf gene.When 7 species of mutans streptococci were amplified by PCR using 3 kinds of primers, the ftf primer showed specific gene amplification in S. mutans, and the gtf primer 1 in S. cricetus, S. sobrinus and S. downei. The gtf primer 2 showed specific gene amplification in all 7 species of mutans streptococci.The presence of S. mutans and S. sobrinus in clinical samples (saliva and plaques) could be evaluated by these 3 kinds of primers. Comparisons of EcoRI fingerprints to determine the 7 species of mutans streptococci showed the different digestion patterns in each species.