Research Article: Fretibacterium sp. human oral taxon 360 is a novel biomarker for periodontitis screening in the Japanese population

Date Published: June 19, 2019

Publisher: Public Library of Science

Author(s): Thatawee Khemwong, Hiroaki Kobayashi, Yuichi Ikeda, Takanori Matsuura, Takeaki Sudo, Chihiro Kano, Ryo Mikami, Yuichi Izumi, David M. Ojcius.


Periodontitis is a common inflammatory disease, leading to bone destruction and tooth loss. Screening for periodontitis is important in preventing the progress of this disease. Various types of bacteria have been examined as potential screening targets, but only culturable pathogenic bacteria have been considered candidates. Recently, the various uncultivable bacteria have been identified in microbiome studies, but the value of these bacteria in periodontitis screening remains unknown.

The aim of this study was to evaluate the diagnostic use of uncultivable bacteria Fretibacterium sp. HOT 360 and TM7 sp. HOT 356 for periodontitis screening in the Japanese population.

Stimulated saliva samples were collected from 217 participants (periodontitis group, n = 157; healthy group, n = 60). The two uncultivable bacterial species selected were: Fretibacterium sp. human oral taxon 360 (Fretibacterium sp. HOT 360) and TM7 sp. human oral taxon 356 (TM7 sp. HOT 356). The levels of these two bacterial species were compared with those of Porphyromonas gingivalis (P. gingivalis), a keystone pathogen in periodontitis. These three species of bacteria were then quantified using qualitative real-time polymerase chain reaction (qPCR) with specific primers and Taqman probes. Statistical analysis was performed by SPSS 20.0 software. P value was statistically significant at .05.

The populations of uncultivable bacterial species TM7 sp. HOT 356 and Fretibacterium sp. HOT 360 were significantly higher in periodontitis group than in healthy group. Only Fretibacterium sp. HOT 360 showed a significantly positive correlation with such periodontal parameters as probing pocket depth (PPD) and bleeding on probing (BOP).

These findings indicate that uncultivable bacteria Fretibacterium sp. HOT 360 can be used as a saliva-based diagnostic bacterial biomarker for periodontitis screening.

Partial Text

Periodontitis is a common disease that occurs worldwide. It is an inflammatory condition that affects the periodontium, leading to bone destruction and tooth loss [1]. The disease progresses slowly with no symptoms. Early screening is important for preventing the progression of this disease and improving oral health. Diagnosis of periodontitis is limited to clinical parameters such as loss of attachment and radiography. However, these parameters can be determined only by examination conducted by a dentist. It is necessary to establish an efficient screening method showing the progress of periodontitis [2]. Screening using saliva has recently become a common screening method. Saliva is a diagnostic tool that is established in the medical and dental fields. Collection of saliva is straightforward and non-invasive, and can be performed by an individual in a home setting [2]. Saliva contains various factors including dental biofilm, gingival crevicular fluid [3], and microorganisms [4]. Periodontal pathogenic bacteria in saliva are associated with symptoms of periodontal disease [5].

Recently, saliva screening is a convenient and non-invasive method that is becoming more common in oral disease studies, and in screening for dental caries and periodontitis. The subgingival plaque or gingival crevicular fluid were reported as the samples for evaluated the periodontitis status but these techniques were not convenient for periodontitis screening in large community scale [25]. Moreover, saliva can provide a cost-effective approach for the screening of large populations [26]. Whole saliva can be collected under no stimulation, or using methods such as mechanical stimulated or administration of mild acids [27]. In this study, we collected stimulated saliva because it is more rapid and simpler for participants who were hyposalivation or xerostomia. However, the technique used to collect saliva can affect the levels of certain biomarkers. Some biomarkers for periodontitis, such as tumor necrosis factor-alpha, C-telopeptide pyridinoline cross-links of type I collagen, and receptor activator of nuclear factor kappa-B [28], are sensitive to salivary collecting techniques [29].

In our study, some of patients presented with various depths of PPD but absence of BOP. Therefore, the data we were able to obtain with respect to percentage of BOP were scant and presented a limitation in this study. In our future studies on gingivitis, we intend to confirm that Fretibacterium sp. HOT 360, P. gingivalis, and TM7 sp. HOT 356 are associated with BOP.