Streptococcus strain C17T as a potential probiotic candidate to modulate oral health

In the microbiome, probiotics modulate oral diseases. In this study, Streptococcus strain C17^T was isolated from the oropharynx of a 5-year-old healthy child, and its potential probiotic properties were analysed using human bronchial epithelial cells (16-HBE) used as an in vitro oropharyngeal mucosal model. The results demonstrated that the C17^T strain showed tolerance to moderate pH ranges of 4–5 and 0·5–1% bile. However, it was more tolerant to 0·5% bile than 1% bile. It also demonstrated an ability to accommodate maladaptive oropharyngeal conditions (i.e. tolerating lysozyme at 200 μg ml^?1). It was also resistant to hydrogen peroxide at 0·8 mM. In addition, we found out that the strain possesses inhibitory activities against various common pathogenic bacteria. Furthermore, C17^T was not cytotoxic to 16-HBE cells at different multiplicities of infection. Scanning electron microscopy disclosed that C17^T adhesion to 16-HBE cells. Competition, exclusion and displacement assays showed that it had good anti-adhesive effect against S. aureus. The present study revealed that Streptococcus strain C17^T is a potentially efficacious oropharyngeal probiotic.