Exploring the Dynamic Core Microbiome of Plaque Microbiota during Head-and-Neck Radiotherapy Using Pyrosequencing

Abstract

Radiotherapy is the primary treatment modality used for patients with head-and-neck cancers, but inevitably causes microorganism-related oral complications. This study aims to explore the dynamic core microbiome of oral microbiota in supragingival plaque during the course of head-and-neck radiotherapy. Eight subjects aged 26 to 70 were recruited. Dental plaque samples were collected (over seven sampling time points for each patient) before and during radiotherapy. The V1–V3 hypervariable regions of bacterial 16S rRNA genes were amplified, and the high-throughput pyrosequencing was performed. A total of 140 genera belonging to 13 phyla were found. Four phyla (Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria) and 11 genera (Streptococcus, Actinomyces, Veillonella, Capnocytophaga, Derxia, Neisseria, Rothia, Prevotella, Granulicatella, Luteococcus, and Gemella) were found in all subjects, supporting the concept of a core microbiome. Temporal variation of these major cores in relative abundance were observed, as well as a negative correlation between the number of OTUs and radiation dose. Moreover, an optimized conceptual framework was proposed for defining a dynamic core microbiome in extreme conditions such as radiotherapy. This study presents a theoretical foundation for exploring a core microbiome of communities from time series data, and may help predict community responses to perturbation as caused by exposure to ionizing radiation.

Microbiota and their role in the pathogenesis of oral mucositis

“…With regard to irradiation therapy, studies by Shao et al () and Hu et al () suggest that the core oral microbiome is modulated over time. Of particular interest is the recent study of Hu et al () on the ‘dynamic core microbiome’ of plaque microbiota in the diseased condition after radiotherapy. Dental plaque samples of 8 subjects were collected before and weekly during radiotherapy, and high‐throughput pyrosequencing of the bacterial 16S rRNA genes was performed.…”

Effects of Irradiation on Epithelial Wound Healing and Microbial Diversity in an in-vitro Oral Mucosa Model

“…Unlike Granulicatella and Gemella that are omnipresent in the oral cavity, Rothia is mostly linked with tooth surfaces [9]. Interestingly, Rothia species were reported to become more abundant in head and neck cancer patients during radiotherapy, whereas Granulicatella species were shown to decrease after irradiation [10,11]. Therefore Granulicatella species are not likely to be the causing agents of post-radiation diseases [11].…”

Low-dose irradiation affects the functional behavior of oral microbiota in the context of mucositis

“…Recent data indicate that both chemo-and radiotherapy are associated with a decrease in microbial diversity, 5,6,56 which is believed to be correlated with a poor health prognosis. Our data indicate that apart from the composition, radiation therapy can also change the functional behavior of the resident oral microbiome.…”

“…4 Overall, there is convincing data to conclude that irradiation changes the oral core microbiome over time 5,6 with Gram-negative species becoming more abundant 7-9 together with Candida spp. 8,10-12 and Lactobacillus spp.…”