# Characteristics of Clinical Isolates of _Streptococcus mutans_
## 3 Results and Discussion
mutans_ reference strain UA159, in each case obtaining a product of the expected size. Analysis of 26 TCS genes was performed for all 60 strains using multiplex PCR. The results of TCS VickKR and TCS CiaHR analysis for selected isolates are presented (Figures 1 and 2). Amplification was obtained for all 26 genes analysed in all 60 strains. Based on the present study, TCS are present in the clinical isolates of _S. mutans_ tested, as 26 TCS genes were confirmed in all of them, which may indicate that there is a good place for drugs and other anti-caries precisely because of their prevalence. However, it should be borne in mind that the determination of the presence of genes does not provide information on the level of their expression in individual strains; there may be fundamental differences. The acid-forming activity is essential to the process of the formation of caries, which leads to damage of the enamel and initiates the tooth decay process. The expression level of TCS and the activity of genes that encode proteins related to the fermentation of sugars should be assessed in separate studies. The presented results give insight into the biochemical and genetic characteristics of the collected set of isolates, and the results are fully reproducible. The existence of common features of _S. mutans_ strains obtained from mothers and their children has been documented in the literature on the subject [23]. Based on the research performed for this study, it can be concluded that there are no significant differences in biochemical and genetic characteristics and there are no differences in the biofilm formation capacity between the strains derived from children and adults, and among those in children or adults alone. The _S. mutans_ strains, which were the subject of the study, are characterised by high similarity. It should be noted that the strains were isolated from different, unrelated individuals who did not live together. Efforts have been made to identify _S. mutans_ strains of special risk [18]. In the case of such strains, dentists should take preventive measures to protect patients from developing caries. Strains of _S. mutans_ are also involved in the colonisation of dentures and implants. The colonisation of implants can lead to the development of peri-implantitis. The risk of poor denture hygiene is particularly high in the case of elderly people. The presence of biofilm on medical products can lead not only to oral infections, such as denture stomatitis,  
Figure 1: Multiplex PCR of vick and vir R genes (TCS VickKR) for randomly selected _S. mutans_ clinical isolates. Size of the products: _vick_-510 bp, _vir R_-211 bp. 1, size standard; 2, _S. mutans_ UA 159 positive control; 3–11, clinical isolates from adults; 12–20, isolates from children. Figure 2: Multiplex PCR of ciaH and cia R genes (TCS CiaHR) for randomly selected clinical isolates. Size of the products: ciaH-529 bp, cia R-211 bp. 1, size standard; 2, positive control, _S. mutans_ UA 159; 3–11, clinical isolates from adults; 12–20, isolates from children. but also to aspiration pneumonia and chronic obstructive pulmonary disease. Factors such as the presence of TCS systems and the level of biofilm formation seemed to be important elements in the characterisation of _S. mutans_, which would allow one to identify the most dangerous strains. Based on the obtained results, all _S. mutans_ strains isolated from the oral cavity have TCS systems and produce high levels of biofilm. The collected data indicate that those characteristics are of key importance for the biology of _S. mutans_ and do not allow those features to be used for strain differentiation.