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Non-mutans streptococci in patients receiving radiotherapy in the head and neck area
1Department of Cariology, Endodontology and Operative Dentistry, School of Stomatology, Peking University, Beijing, China.
Objective:
To study mutans and non-mutans streptococci in patients after radiotherapy of the head and neck.
Methods:
Oral rinse samples collected from nasopharyngeal carcinoma patients before and after radiotherapy were diluted and cultured on nonselective and selective media for enumeration of total cultivable plaque flora, mutans and non-mutans streptococci and lactobacilli. Non-mutans streptococci were identified biochemically and by 16S rDNA sequence homology analysis.
Results:
After irradiation, mutans streptococci were not isolated; the levels of Streptococcus mitis and lactobacilli increased significantly. The level of Streptococcus salivarius increased, but the significance was the borderline. The level of Streptococcus sanguis decreased significantly after irradiation. The abundance of other oral streptococci species showed no significant changes.
Conclusions:
S. mitis and S. salivarius are the predominant non-mutans streptococci in the high-caries-risk oral flora following radiotherapy.