Carious Lesions and Enamel Surfaces Harbor Distinct Mutans Streptococci Strains

Objectives: Mutans streptococci (MS) are one of the major microbiological determinants of dental caries.  The objectives of this study, using a cohort of 20 children, are to identify distinct MS strains that are harbored within carious and white spot lesions (WSLs) vs. non-carious enamel surfaces.

Methods:   Dental plaque from children (N=20; ages 3-5) was collected from multiple surfaces along the entire dentition, or from individual sites, including enamel surfaces, carious lesions and WSLs.  MS isolates (N between 10 and 20 isolates) from each collection site were selected on mitis salivarius agar containing bacitracin and were subjected to Gram stain analyses.  Isolates were further characterized by polymerase chain reaction (PCR) for verification as MS and arbitrarily primed-PCR for assignment within genotypic strains.

Results:   The entire dentition specimens were used as an indicator of MS genetic diversity within each child; all children contained 2-7 MS strains. In most cases, carious lesions harbored MS strains that were distinct from strains found within non-carious enamel surfaces.  WSLs typically contained MS strains found within the carious lesions, but tended to contain at least one additional MS strain. In almost all cases, including all ten MS isolates from each patient, Patients EE and FF, carious lesions harbored single dominant MS strains when compared to the entire pool of MS isolates obtained from the entire dentition.  

Conclusions:   Carious lesions and non-carious enamel surfaces harbor distinct MS genetic strains that may be reflective of the strain’s cariogenicity potential.  WSLs, or developing carious lesions, also contain the dominant MS strain found within carious lesions.  Enamel surfaces tended not to have MS strains found in carious lesions and WSLs.   Supported by OHSU School of Dentistry.