Streptococcus Mutans from American Indian Children: Biofilm Formation

Objectives: American Indian children suffer from one of the worst caries rates in the world, with evidence accumulating that the situation is not improving, despite multiple intervention and educational programs. We have previously shown that American Indian children with rampant caries have unique clonal types of SM based on AP-PCR fingerprinting. The purpose of this study was to assess sucrose-driven biofilm formation of previously identified clonal types of SM from American Indian children. Methods: Multiple SM isolates were characterized into 11 clonal types (1-2 per subject) based on AP-PCR fingerprints. Clonal types were from both caries-free and rampant caries (≥7 carious teeth). Biofilm formation ability of the clonal types was performed using a microtiter plate assay. Bacteria were cultured in TSB-YE supplemented with 1% glucose and 1% sucrose. Plates were incubated in 5% CO₂ for 48 hours. Replicate wells were stained with crystal violet for microscopy. Biofilms were harvested and homogeneous suspensions prepared. Numbers of biofilm cells were determined by spiral-plating and grid counting. Analysis of log₁₀ transformed counts was done with a one-way ANOVA. Results: Examination of stained biofilms showed differences in architecture of clonal types from caries-free subjects with biofilms exhibiting a more flocculent and aggregate development. Analysis of the numbers of colonized cells, however, did not reveal statistically significant differences. Conclusions: Statistical differences were not observed in ability of different clonal types of SM to form biofilms based on overall numbers colonizing. However, differences were observed in the biofilm architecture in SM clonal types from caries-free children. Ongoing studies are focusing on these biofilm architecture differences. Supported by University of Iowa, College of Dentistry Dental Research Award.