PCR for detection of mutans streptococci in human dental plaque

Abstract

Mutans streptococci such as Streptococcus mutans and Streptococcus sobrinus have been implicated in human dental caries. The diversity of detection frequencies of mutans streptococci from human dental plaque has been reported, and it may be due to the differences in detection sensitivity, subject age and/or target genes tested. In this study, firstly the detection sensitivities were compared between the nested (second) and direct PCR. Secondly, detection of mutans streptococci from human dental plaque was performed with PCR using three different primers based upon 16S ribosomal RNA, glucosyltransferase and dextranase genes, and their detection frequencies were compared. 144 human dental plaque samples were analyzed, and a PCR with primers for 16S rRNA gene was shown to be more sensitive for detecting S. mutans and S. sobrinus than with those for glucosyltransferase and dextranase genes (except for detection of S. sobrinus in ages 0–1). Utilizing PCR with primers based upon the 16S rRNA gene, S. mutans was detected from all of the samples while the detection frequencies of S. sobrinus were lower (10%) than those of S. mutans, and S. sobrinus were likely detected in the subjects of deciduous attained-dentition and mixed-dentition stage. These results suggest that the 16S rRNA gene-based nested PCR method is a rapid and sensitive method for the detection of mutans streptococci, and may also be suitable for carrying out large-scale studies on the cariogenicity of mutans streptococci.