Streptococcus anginosus infection in oral cancer and its infection route

OBJECTIVE: To elucidate a possible involvement of Streptococcus anginosus in oral cancer, we assessed the frequency of S. anginosus infection in oral cancer tissues, and investigated its infection route. MATERIALS AND METHOD: The tissue specimens were obtained from 46 oral cancer and three precancerous leukoplakia subjects. Frequency of S. anginosus infection was assessed by a species-specific polymerase chain reaction (PCR) assay. The genotype of the clinical isolates taken from cancer tissue and dental plaque samples was analyzed using pulsed-field gel electrophoresis (PFGE). RESULTS: S. anginosus DNA was frequently detected in squamous cell carcinoma (19/42), but not in other types of cancer (lymphoma and rhabdomyosarcoma) or leukoplakia samples. A subject-based analysis revealed that S. anginosus was solely detected in dental plaque and not in saliva from all 19 S. anginosus-positive squamous cell carcinoma cases. Further, the genotype of S. anginosus isolated from cancer tissue was identical to that from dental plaque of the same patients. CONCLUSION: Infection of S. anginosus could occur frequently in oral squamous cell carcinoma and that dental plaque could be a dominant reservoir of the S. anginosus.