S. mutans, Aciduric and Acidogenic Bacteria from Early Childhood Caries

Objectives: This study compared detection of Streptococcus mutans (Sm) aciduric and acidogenic isolates between severe early childhood caries (S-ECC) and caries-free (CF) children.

Methods: S-ECC and CF children (2-5 years)were recruited. Incisor (I), interproximal Molar (M) tooth and Tongue (T) plaque samples were cultured on Blood (pH7), Acid (pH5), and the selective mutans agars, TYCSB and MSB. Isolates from Molar samples from acid and blood agar were tested for final pH in glucose broth.

Results: 33 S-ECC children, mean age 3.9 yr and 12 CF children mean age 3.4 yr were sampled. 50% children were male. Average extent of caries was 6.3 teeth into dentine, and 3.8 teeth into pulp. Sm counts from TYCSB were higher than for MSB by 6x Incisor, 20x Molar, and 2x Tongue samples. There were higher Sm counts from S-ECC than CF children and Sm was detected from I, M, T sites from 87%, 90% and 87% S-ECC, 30%, 44%, 45% CF children respectively. S. sobrinus was detected only in the S-ECC children. Acid and blood agar counts were 6 x greater from S-ECC than CF. The ratio of acid to blood counts did not differ between S-ECC and CF. A higher proportion of isolates from acidic agar reduced the pH below 4.5 than blood agar from both S-ECC and CF children. The tongue had a higher proportion of aciduric isolates than tooth plaque samples.

Conclusions: TYCSB more sensitive than MSB for S. mutans detection. Levels of aciduric species were higher from caries children indicating a higher total load of acid-producing species from severe caries. Acid agar selected for acidogenic, or acidogenic variants of, species. Non Sm acidogenic isolates are potentially new caries pathogens. Supported by NIH/NIDCR Grant DE-015847.