Streptococcus mutans and Lactobacillus Prevalence and Acidogenicity in Caries

Objectives: Caries is a prevalent chronic disease in the United States and is the second most common disease in children. In particular, 76% of 2-4 year old Native American Indians (AI) have a history of decay. Methods: We have analyzed 7 AI caries active (CA) subjects and 6 AI caries inactive (CI) subjects to enumerate bacterial species associated with caries in addition to assessing the acidogenicity potential of AI plaque samples and S. mutans (SM) clonal types involving 5%, 2.5%, and 1% solutions of sucrose, glucose, maltose, and lactose substrates. Plaque samples were spiral plated to enumerate S. mutans (MSKB agar), Aciduric bacteria (ASA agar), Lactobacillus species (Rogosa agar), and total bioburden (blood agar). Four SM isolates from CA and CI subjects respectively, were characterized as 8 different clonal types based on AP-PCR fingerprints using primers OPA 2 and OPA 13. The eight SM clonal types and four respective CA and CI plaque samples were inoculated into ESTYP-YE (.025mls/25 mls) and carbohydrate solutions (.1ml/5 mls, final A₆₆₀ = .2) and subsequent pH/A₆₆₀ readings were recorded to assess culture acidogenicity. Results: SM and Lactobacillus concentrations for CA and CI subjects were significantly different. Average SM concentrations were 4.03 x 10⁵ CFU/sample (CA) and 3.35 x 10 ³ CFU/sample (CI) whereas average Lactobacillus concentrations were 4.03 x 10⁴ CFU/sample (CA) and 3.0 x 10¹ CFU/sample (CI). To date, initial acidogenicity assays demonstrated significant differences between S. mutans and S. sobrinus ATCC controls. However, these differences were not seen with the majority of SM isolates in initial assays. Additional assays involving complex carbohydrate substrates are in progress. Conclusions: A significant association between S. mutans and Lactobacillus colonization and caries level was detected in a Native American Indian population. Supported by NIH 1 RO1 DE017736-01A1.