This study compared SYBR Green real time quantitative polymerase chain reaction (qPCR) with standard plate counting for the enumeration of Streptococcus mutans in oral samples. Oral samples (N=710) were collected from high caries risk children for quantification of S. mutans using primer pairs by qPCR. S. mutans copy number (CN) was interpolated from qPCR quantification cycle (Cq) of samples compared to a S. mutans UA159 standard suspension. CN sample results were evaluated in relation to standard plate count (SPC) results obtained from each sample following culture on Petri plates using S. mutans selective media reported as colony forming units (CFU). Mean qPCR CN were found to be higher than SPC CFU (1.3 × 106 and 1.5 × 105, respectively). qPCR was usually higher in individual samples and qPCR detected the presence of S. mutans 84% (231/276) of time that SPC did not, compared to 33% (4/12) when qPCR failed to detect. qPCR was found to be more sensitive for detection of S. mutans from oral samples; a method that is not dependent on the viability of the sample taken and, therefore, is proposed as a more reliable and efficient means of quantification of S. mutans.

The aim of this study was to determine the reproducibility of individual versus pooled plaque sampling of permanent first molars (PFM) to quantitate Streptococcus mutans (SM)/total streptococci (TS). Ten individual and pooled plaque samples were collected from 35 subjects, randomly assigned to individual-first or pooled-first group. Plaque samples were processed and quantified for SM and TS. SM/TS ratio was used to determine the reproducibility within two group samples. Mean percentage of SM/TS in both methods were not significantly different. However, within subject detection of SM was found to be significantly more sensitive for individual sampling method. Despite the lack of a difference between both methods for SM/TS quantitation, the difference in SM detection suggests that individual sampling is more sensitive.