Lack of association between Streptococcus oralis and recurrent aphthous stomatitis

In the present study, the potential involvement of Streptococcus oralis in the aetiology of recurrent; aphthous stomatitis (RAS) was investigated usin g the polymerase chain reaction (PCR). Biopsies from 28 RAS patients were a nalysed, in addition to 20 oral lichen planus (OLP) and 13 normal biopsies that were used as controls. PCR was carried out using a primer pair that ta rgets the D-alanine:D-alanine ligase gene and detects DNA from both S. oral is and the closely related species Streptococcus mitis. Discrimination betw een these two species was achieved by digestion of PCR products with the re striction endonucleases HaeIII and HindIII, which both give distinct restri ction profiles for each species. S. oralis DNA was detected in 8 of 28 (29% ) RAS samples, 10 of 20 (50%) OLP samples and 6 of 13 (46%) normal samples. These results suggest that S. oralis is not of primary aetiological signif icance in RAS.