The Contribution of the Human Oral Microbiome to Oral Disease: A Review

Abstract

The oral microbiome is an emerging field that has been a topic of discussion since the development of next generation sequencing and the implementation of the human microbiome project. This article reviews the current literature surrounding the oral microbiome, briefly highlighting most recent methods of microbiome characterization including cutting edge omics, databases for the microbiome, and areas with current gaps in knowledge. This article also describes reports on microorganisms contained in the oral microbiome which include viruses, archaea, fungi, and bacteria, and provides an in-depth analysis of their significant roles in tissue homeostasis. Finally, we detail key bacteria involved in oral disease, including oral cancer, and the current research surrounding their role in stimulation of inflammatory cytokines, the role of gingival crevicular fluid in periodontal disease, the creation of a network of interactions between microorganisms, the influence of the planktonic microbiome and cospecies biofilms, and the implications of antibiotic resistance. This paper provides a comprehensive literature analysis while also identifying gaps in knowledge to enable future studies to be conducted.

Keywords: 16S rRNA gene sequencing; Fusobacterium nucleatum; Leptotrichia; Porphyromonas gingivalis; Prevotella; Streptococcus mutans; oral cancer; oral disease; oral microbiome.

Figure 1

The role of Fusobacterium nucleatum in the inflammation and ultimately the increase in cell proliferation of host cells. Both FadA and Fap2 are encoded by F. nucleatum, and their individual pathways are also shown [129]. FadA utilizes the E-cadherin complex while Fap2 adheres to the galactose sensitive pathway through the use of N-acetylgalactosamine (Gal/NAc) [131]. F. nucleatum provokes a variety of host responses including the stimulation of IL-6, IL-8, IL-17, and TNF α [138]. During a healthy state, this inflammation leads to wound repair and healing. However, during a diseased state, this can lead to DNA damage and cancer.