Characterization of Novel Bifidobacteriaceae, Metascardovia criceti and B. tsurumiense

Metascardovia criceti and Bifidobacterium tsurumiense are novel species of Bifidobacteriaceae that were isolated from dental plaque of hamsters fed with a high-carbohydrate diet. These species appeared to be dominant colonizers for the formation of plaque in these experimental animals. Objectives: (i) To determine the growth rate and acid production of these bacterial species in the presence sugar supplements; and (ii) To characterize the coaggregation profiles of these species with other known oral organisms found in plaque. Materials & Methods: Bifidobacterium species and related genera, including Scardovia, Parascardovia, Alloscardovia, and selected lactic acid-producing species were used for these experiments. For testing the acidogenicity and growth rate, the test strains were grown in Trypticase soy broth supplemented with sugars in concentrations ranging from 0 to 5%. Growth rate was determined by measuring the optical density of the test cultures at 620 nm, and acidogenicity of test organisms was determined by measuring the pH of the culture after incubation at 35^oC for 16 h under anaerobic conditions. Coaggregation assay of the test organisms was performed according to the methods of Cisar et al. Results: The growth rates and acid production for M. criceti and Bifidobactrium strains were strongly enhanced in the presence of glucose, fructose, lactose and sucrose. These test strains showed a species-specific growth pattern in relation to the type of sugars used. Acid production was the highest among M. criceti, B. tsurumiense, and Streptococcus mutans. Further, of all the strains tested, M. criceti, B. tsurumiense, Parascardovia, and Alloscardovia strains coaggregated strongly with the black-pigmented anaerobes. Conclusion: These novel strains showed sugar-dependent growth and acid production. These strains, together with streptococci, might be involved in the development of dental diseases in experimental animals.