# Periodontal Condition and Subgingival Microbiota Characterization in Subjects with Down Syndrome
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Periodontal Health (H)**} & \multicolumn{2}{c}{**Gingivitis (G)**} & \multicolumn{2}{c}{**Periodontitis (P)**} & \multicolumn{2}{c}{**\(p\) Value**\({}^{*}\)} \\  & \multicolumn{2}{c}{**(_n = 62_)**} & \multicolumn{2}{c}{**(_n = 34_)**} & \multicolumn{2}{c}{**(_n = 28_)**} & \multicolumn{2}{c}{**\(p\) Value**\({}^{*}\)} \\ \hline
**Proportions** & **Median** & **IQR** & **Median** & **IQR** & **Median** & **IQR** & **All** \\ \hline _A. actinomycetemcomitans_ & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & \\ _P. gingivalis_ & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.58\% & 0.37 \\ _P. intermedia_ & 0.00\% & 0.05\% & 0.00\% & 0.06\% & 0.01\% & 0.41\% & 0.24 \\ _T. forysthia_ & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.24 \\ _P. micra_ & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.40 \\ _F. nucleatum_ & 1.29\% & 2.77\% & 0.91\% & 3.31\% & 0.59\% & 1.76\% & 0.21 \\ _C. rectus_ & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.48 \\ _E. corrodens_ & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.28\% & 0.01 * \\ _Capnocytophaga_ spp. & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.26 \\ _A. odontolytica_ & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% & 0.51 \\ \hline \hline \end{tabular}  
* \({}^{*}\)Proportions of total anaerobic microbiota (Kruskal-Wallis p value); for comparison between groups, they were available just for _E. corrodens_ (H-G, 1.00; G-P, 0.13; H-P, 0.01 *).
* Statistically significant differences. _A. actinomycetemcomitans_: _Aggregatibacter actinomycetemcomitans_; _P. gingivitis: _Porphyomonas gingivitis_; _T. forysthia_: _Tannerella forysthia_; _P. micra_. Partimonas micra_; _F. nucleatum: _F. nucleatum: _F. nucleatum: _C. rectus_: _Campylobacter rectus_; _E. corrodens_; _E. Ekorella corrodens_; _A. odontolytica_: _Actinomycetes aortolyticus_.  
\end{table} 
Table 5: Microbiological findings (culture), with proportions of total anaerobic microbiota in percentage, expressed as medians and interquartile ranks (IQR), for each study group, with the appropriate comparisons. For _A. actinomycetemcomitans_, low frequencies of detection in the three study groups were reported in the present study. Much higher frequencies were detected in previous studies [20,37]. These differences could be explained by geographical variability, since a low prevalence of this bacterium has been reported in Spain [40,41] or due to technical aspects, such as the use of different probe-primers in the PCR technique or to differences in the patient selection process. Higher counts and frequencies, for _T. forysthia_ and _A. actinomycetemcomitans_, were reported when using qPCR, compared with culture. Similar results have been found in previous comparative studies [42]. These differences could be explained by the ability of qPCR to detect DNA of both viable and non-viable bacteria and to the lower detection limits of qPCR [32,38]. In addition, detection for _T. forysthia_ by culturing is challenging [43,44], resulting in higher sensitivity and lower specificity when comparing qPCR technique _versus_ culture [32,43,45]. However, the overall microbial tendency of an increase in prevalence for the three main target bacterial species from periodontal health to gingivitis and to periodontitis, was similar irrespective of the applied microbiological diagnostic technique. The use of different microbiological technologies makes difficult to interpret the results from different studies, although common trends can be identified. In the present study, in which two complementary techniques were used, qPCR yielded higher counts for the three main target bacterial species, and higher prevalence for _T. forysthia_ and _A. actinomycetemcomitans_, than culturing techniques, but the same tendency was observed with both methods, that is, an increase in prevalence/counts for the three main target bacterial species from health to gingivitis and to periodontitis.