Effects of Streptococcus thermophilus on volatile sulfur compounds produced by Porphyromonas gingivalis

Halitosis as oral malodour is an unpleasant odour caused by volatile sulfur compounds (VSCs). VSCs are produced primarily by anaerobic bacteria that abundantly produce proteinase as trypsin-like enzyme. General therapies, such as mouthwash and plaque control, do not provide a continuous effect on oral halitosis. Streptococcus thermophilus is a probiotic bacterium that is beneficial for human health. The aim of this study was to evaluate the effect of S. thermophilus on Porphyromonas gingivalis-producing VSCs and to analyze the inhibitory mechanism of halitosis. P. gingivalis was cultured with or without S. thermophilus, and the emission of VSCs from the spent culture medium was measured by gas chromatography. In order to analyze the inhibitory effect, the antibacterial activity of S. thermophilus against P. gingivalis was assessed. After the spent culture medium or whole bacterial of S. thermophilus was mixed with the spent culture medium of P. gingivalis, VSCs were again measured by gas chromatograph. When S. thermophilus and P. gingivalis were co-cultivated, VSCs were present at a lower level than those of single-cultured P. gingivalis. S. thermophilus inhibited growth of P. gingivalis, and the whole bacteria and the spent culture medium of S. thermophilus reduced emission of VSCs gas. S. thermophilus may reduce oral malodour by inhibition of P. gingivalis growth and neutralizing VSCs with their metabolites or themselves.