Mouth-rinsed water can be substitute for saliva as a sampling method of oral microbiota.

Epidemiological studies using saliva revealed relationship between the oral microbiome and many oral and systemic diseases. However, saliva collection can be a burden for subjects with low saliva flow. Mouth-rinsed water, which is a liquid that rinsed oral cavity with water, can be used as an alternative sampling method of saliva for collecting oral microbiome because of the ease of collection from these subjects. The purpose of this study was to verify whether mouth-rinsed water is a suitable substitute for saliva to analyze the oral microbiome. We collected samples from mouth-rinsed water, stimulated saliva, unstimulated saliva, and tongue coating from 10 healthy subjects, and compare these microbial diversity and composition for next-generation sequencing of the 16S rRNA encoding genes. The results showed that microbial diversity of mouth-rinsed water was similar to unstimulated saliva and stimulated saliva, and significantly higher than that of tongue. The microbial composition of mouth-rinsed water at the species level also showed very high correlation with the composition of unstimulated saliva and stimulated saliva compared with the composition from tongue coating. These results mean that mouth-rinsed water can be substitute for saliva as a sampling method of oral microbiota.