Biology of Oral Streptococci

Abstract

Summary Bacteria belonging to the genus Streptococcus are the first inhabitants of the oral cavity which can be acquired right after birth and thus play an important role in the assembly of the oral microbiota. In this chapter, we will discuss the different oral environments inhabited by streptococci and the species that occupy each niche. Special attention is given to the taxonomy of Streptococcus as this genus is now divided into 8 distinct groups where oral species are found in 6 of them. Oral streptococci produce an arsenal of adhesive molecules that allow them to efficiently colonize different tissues in the mouth. Also, they have a remarkable ability to metabolize carbohydrates via fermentation thereby generating acids as byproducts. Excessive acidification of the oral environment by aciduric species such as Streptococcus mutans is directly associated with the development of dental caries. However, less acid-tolerant species such as Streptococcus salivarius and Streptococcus gordonii produce large amounts of alkali displaying and important role in the acid-base physiology of the oral cavity. Another important characteristic of certain oral streptococci is their ability to generate hydrogen peroxide that can inhibit the growth of S. mutans. Thus, oral streptococci can also be beneficial to the host by producing molecules that are inhibitory to pathogenic species. Lastly, commensal and pathogenic streptococci residing in the oral cavity can eventually gain access to the bloodstream and cause systemic infections such as infective endocarditis.

Association of oral dysbiosis with oral cancer development (Review)

“…Bacteria also play fundamental roles in these processes. Some peroxygenase oral microorganisms are involved in this process producing hydrogen peroxide (H 2 O 2 ) and include Bifidobacterium adolescentis, Lactobacillus acidophilus, L. fermentum, L. jensenii, L. minutus (90,108), Streptococcus gordonii, S. mitis, S. oligofermentans, S. oralis, and S. sanguinis (109).…”

Reconstruction and Validation of a Genome-Scale Metabolic Model of Streptococcus oralis (iCJ415), a Human Commensal and Opportunistic Pathogen

“…These bacteria exist in a complex metabolic relationship with other oral streptococci, as well as other species residing in the oral cavity. These interactions are thought to have an influence on the development of certain oral diseases in humans, e.g., caries (Kreth et al, 2009;Nascimento et al, 2009;Abranches et al, 2018). Sometimes these MGS are able to escape their oral niche and cause an infection of the heart valves, infective endocarditis (IE), a severe disease with a high mortality even with proper treatment.…”

Identification of novel mutational signatures in Asian oral squamous cell carcinomas associated with bacterial infections

“…Focussing on tumour TC1, we identified several genera of bacteria including Lachnoanaerobaculum, Prevotella, Anaerococcus and Streptococcus (Supplementary Figure S16). All these bacterial genera are common oral symbionts (Downes et al 2008;Labutti et al 2009;Hedberg et al 2012;Abranches et al 2018). Because of the rareness of the mutational signatures discovered in this study, it is unlikely that such common oral bacteria would be causal.…”