Detection and Identification Supragingival Plaque S.m by FISH and FC

Objectives:To establish a protocol for Fluorescence In Situ Hybridization and Flow Cytometry (FC-FISH) detection of streptococcus mutans of supragingival plaque sample,and provide reference data for the assessment of an individual's risk and disease incidence. Methods: 30 Chinese pre-school children were selected in this study, 15 in caries-free group (CF, dmfs=0), and 15 in caries-susceptible group (CS, dmfs≥10). The number of total bacteria and number of S.mutans in each supragingival plaque sample determined by the FC-FISH was calculated and compared to the results obtained by quantitative anaerobic culture. Results: The percentages of S.mutans in plaque range from 1.24% to 3.4% in the CF group (mean 2.25±0.71%) and from 5.04% to 9.7% in the CS group (mean 7.37±1.34%). The statistical analysis of the results indicated a significant difference (P<0.01).S.mutans was cultured from 26(86.7%) of the 30 supragingival plaques. All these culture- positive samples also appeared to be positive by the FC-FISH assay (100% sensitivity).In addition, 2 samples were positive for S.mutans by the FC-FISH but negative by culture. Of the 4 culture-negative samples, 2 were negative by this FC-FISH assay (92.9% specificity).In no case (0%) was a FC-FISH -negative, culture-positive result found. Conclusion: FC-FISH allows a more rapid detection and identification of S.mutans from supragingival plaque compared with standard laboratory methods requiring additional 24¨C48h (including subcultivation and subsequent biotyping).Such non-cultural methods will be useful for quantifying S.mutans in oral cavity and for analyzing biofilm formation.