title: The persistence of Streptococcus mutans in nasopharyngeal carcinoma patients after radiotherapy.
abstract: The aim of the study was to examine the persistence of oral Streptococcus mutans in nasopharyngeal carcinoma patients after radiotherapy. Ten subjects, ranging in age from 20 to 67 years, participated. DMFT/DMFS, salivary level of mutans streptococci and oral health status were recorded. Pooled plaque samples were obtained from the cervical margins and the interproximal regions of all the teeth and the occlusal surfaces of the molars prior to, immediately after, 3 and 6 months after the completion of radiotherapy. At least 10 colonies of S. mutans were isolated from each subject and totally 645 isolates were genotyped by restriction endonuclease analysis. The results showed that the salivary level of S. mutans increased significantly with the reduction of salivary flow rate after radiotherapy. Each subject had at least 1 genotype of S. mutans isolated throughout the follow-up period. In 3 subjects who initially carried 2 or more genotypes, 1 or 2 genotypes of S. mutans could not be detected 3 months after treatment. Moreover, the genotypes that became undetectable were predominant bacteria in the first sampling. The result indicated that most S. mutans genotypes were persistent after radiotherapy but some genotypes that might not adapt to the alteration of oral environment became undetectable.
authors.affiliation: Key Laboratory of Oral Biomedical Engineering (Wuhan University), Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, PR China.
authors.forename: Liuyan
authors.initials: L
authors.lastname: Meng
authors.forename: Jiarong
authors.initials: J
authors.lastname: Liu
authors.forename: Bin
authors.initials: B
authors.lastname: Peng
authors.forename: Mingwen
authors.initials: M
authors.lastname: Fan
authors.forename: Min
authors.initials: M
authors.lastname: Nie
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.forename: Yu
authors.initials: Y
authors.lastname: Gan
authors.forename: Zhuan
authors.initials: Z
authors.lastname: Bian
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000382:microbiology* / Q000532:radiotherapy; D012463:Saliva / Q000382:microbiology / Q000528:radiation effects*; D012472:Salivation / Q000528:radiation effects; D013295:Streptococcus mutans / Q000528:radiation effects*; D011795:Surveys and Questionnaires; D013997:Time Factors