The tongue microbiome in healthy subjects and patients with intraoral halitosis

Intra-oral halitosis (IOH) is an unpleasant odor emanating from the oral cavity. It is thought that the microbiota of the dorsal tongue coating plays a crucial role in this condition. The aim of the study was to investigate the composition of the tongue microbiome in subjects with and without IOH. A total of 26 subjects, 16 IOH patients and 10 healthy subjects were recruited based on their organoleptic score and volatile sulfur compound (VSC) measurements. The composition of the tongue microbiome was studied using the 16s amplicon sequencing of the V3-V4 hyper variable region with an Illumina MiSeq. The sequenced data were analyzed using QIIME, and the sequences obtained were distributed across 7 phyla, 27 genera and 825 operational taxonomic units (OTUs). At a higher taxon level, TM7 was associated with IOH patients whereas Gemellaceae was significantly abundant in the healthy subjects. At OTU level, we found several significant OTUs that differentiated the IOH patients from the controls. These included Aggregatibacter (OTUid 4335776), Aggregatibacter segnis (A. segnis), Campylobacter, Capnocytophaga, Clostridiales, Dialister, Leptotrichia, Parvimonas, Peptostreptococcus, Peptococcus, Prevotella, Selenomonas, SR1, Tannerella, TM7-3 and Treponema in the IOH group. In the control group, Aggregatibacter (OTUid 4363066), Haemophilus, Haemophilus parainfluenza (H. parainfluenza), Moryella, Oribacterium, Prevotella, several Streptococcus, Rothia dentocariosa (R. dentocariosa) and OTU from Gemellaceae were significantly abundant. Based on our observation, it was concluded that the bacterial qualitative composition of the IOH and the control group was almost the same, except for the few above-mentioned bacterial species and genera.