Stability of Streptococcus mutans clonal types in caries-active children

Objectives: We have previously shown that caries-active children in Head Start Programs in Iowa have more S. mutans (SM) clonal types than caries-free children. Moreover, we reported that a preliminary assessment of SM clonal types over time in these children revealed that caries-active children had more complex and stable SM clonal type profiles. The purpose of this study was to expand on these initial findings by examining a greater number of caries-active children. Methods: We have a cryolibrary of 10 SM isolates per subject from Head Start Program children taken at different periods of time over one year. DNA was extracted from 10 isolates per subject from caries-active children at each of these timepoints: baseline, 3 months, and 6 months. Arbitrarily-primed polymerase chain reaction (AP-PCR) was performed. Amplification was performed with the following temperature profile: initially 5 minutes at 94^вкC, followed by 45 cycles of 1 minute at 94 ^вкC (denaturation), 1 minute at 36^вкC (annealing), and 2 minutes at 72^вкC (elongation). Amplification mixture (master mix) consisted of: DNAase free H₂O, 10X amplification buffer, dNTP (0.2 mM), MgCl₂ (7uM), Primers OPA-2 and OPA-13 in separate runs, and Taq Polymerase. Results: SM clonal type profiles were very stable in these children from baseline to the 6 month time point. Moreover, we observed 2-4 clonal types routinely in caries-active children in contrast to caries-free children where we observed mostly one clonal type with occasionally a child with two clonal types. Conclusion: Our data suggest that the clonal type profiles of S. mutans in 3-year-old caries-active children appear to be complex, but stable over time. Caries-free children had less complex profiles, but less stability in the clonal types observed over time. Supported by T32DE0014678-06