Dominance of non-SM acid streptococci: Incipient caries in children

Objectives: Streptococcus mutans (SM) is a major etiological agent in caries; however, evidence suggests other organisms have a role in caries development. We have shown that non-SM acidogenic streptococci were dominant in plaque associated with incipient lesions in young children. This study's purpose was to expand our earlier studies by (1) assessing SM and non-SM acid strep in site-specific plaque from incipient lesions and adjacent sound surfaces, (2) determine the acid adaptation capabilities of non-SM acid strep from incipient lesions, and (3) determine levels of arginolytic bacteria in these subjects. Methods: Five subjects were chosen from 2-4 year old lower SES children enrolled in a study of factors associated with caries. Three plaque samples were taken from each subject: whole mouth swabs, incipient lesions, and adjacent sound surfaces and plated on acid sucrose, MSKB, and arginine agars. Numbers of viable acid-strep, SM, and arginolytic bacteria were determined. PCR was performed on randomly selected isolates using two sets of specific probes for S. mutans, S. sobrinus, S. oralis, S. gordonii, S. salivarius, and S. sanguinis. Assays were conducted on selected isolates to determine acid adaptability. Results: Non-SM acid streptococci dominated incipient lesions with no SM detected by either culture or PCR methods. More non-SM acid streptococci were seen in incipient lesions than adjacent sound surfaces. Random isolates of S. oralis and S. salivarius from incipient lesions exhibited acid adaptability, albeit to a lesser degree than control SM strains. No correlation was found between levels of arginolytic bacteria and caries status. Conclusions: High levels of non-SM acid streptococci were found to be associated with incipient lesions with no detectable SM. As selected non-SM isolates were acid adaptable, these data provide more evidence for a potential role of non-SM acid streptococci as initiators of early carious lesions in young children. Supported by T32DE0014678-06