Characterization of oral bacteria in the tongue coating of patients with halitosis using 16S rRNA analysis

Abstract

There are many studies on the relationship between the tongue coating and halitosis, but few have evaluated the bacterial community present in the tongue coating. This study identified bacteria in the tongue coating in individuals with and without halitosis using 16S rRNA analysis. Forty subjects (mean age, 46.1 ± 15.8 years) who visited the halitosis clinic at the University Dental Hospital between 2016 and 2017 were divided into halitosis (n = 32) and non-halitosis (n = 8) groups according to results from an organoleptic test (OT). Additional measurements via gas chromatography (GC) and the Breathtron® instrument confirmed the groupings as the H₂S, CH₃SH, (CH₃)₂S, and total volatile sulphur compounds (VSC) levels were significantly higher in the halitosis group than in the non-halitosis group. Bacterial diversity was higher in the halitosis group; the median (quartile) values of the Shannon index were 4.46 (4.21, 4.67) in the halitosis group and 3.80 (3.45, 4.30) in the non-halitosis group. Additionally, the median (quartile) values of the Chao-1 index were 84.0 (77.2, 95.0) in the halitosis group and 71.3 (65.0, 81.5) in the non-halitosis group. These differences in bacterial composition and diversity may further the understanding of causes and treatments for halitosis.