Distinctive salivary oral microbiome in patients with burning mouth syndrome depending on pain intensity compared to healthy subjects

Burning moouth syndrome (BMS) is a chronic pain condition similar to neuropathic pain. It is characterized by a persistent burning sensation in the oral cavity. Despite the lack of clarity regarding the etiology of BMS, recent studies have reported an association between the gut microbiome and neuropathic pain. However, few studies have investigated the association between the oral microbiome and orofacial pain, such as BMS. This study aimed to compare the oral microbial profiles of healthy controls (HC) and patients with BMS. The BMS group was further divided into BMS_low and BMS_high groups according to pain intensity. A total of 60 patients with BMS (BMS_low, n = 16; BMS_high, n = 44) and 30 HC provided saliva samples, which were sequenced and analyzed for the V1-V2 region of the 16S rRNA gene. The alpha diversity was similar among the three groups. However, a significant difference in the distribution of microbiome composition was observed between BMS_high and HC, as revealed by the Bray-Curtis distance analysis (P < 0.01). At the genus level, Prevotella and Alloprevotella were the most abundant genera in the BMS group. Compared to HC, BMS_high exhibited a relatively higher abundance of bacterial species. Some bacteria, including Prevotella spp., exhibit an increasing pattern with subjective pain intensity. These results suggest the potential involvement of oral microbiota in BMS pathogenesis. Additionally, variations in the microbiome may occur not only in the presence or absence of pain, but also with pain severity.