The human body hosts a vast ecosystem of microorganisms, including bacteria. These microscopic inhabitants, the microbiome, reside in various body parts, especially the oral cavity. Among this diverse bacterial community is Streptococcus gordonii, a bacterium commonly found in the human mouth. Not all bacteria are detrimental; some, like Streptococcus gordonii, play complex roles, contributing to health while also having the potential to cause disease under specific conditions.
What is Streptococcus Gordonii?
Streptococcus gordonii is a species of Gram-positive bacteria, characterized by its spherical or ovoid shape and tendency to form chains. It belongs to the Streptococcus genus and is categorized within the alpha-hemolytic (viridans) sanguinis group. While its primary habitat is the human oral cavity, it can also be found in other areas such as the upper respiratory tract and intestines.
This bacterium is a facultative anaerobe, able to grow with or without oxygen. Its genome was fully sequenced in 2016. Streptococcus gordonii is non-motile and does not form spores.
Its Role in Oral Health
Streptococcus gordonii functions as a commensal bacterium in the oral microbiome, generally coexisting harmoniously with its host. It is recognized as one of the initial colonizers of tooth surfaces, playing a significant role in the formation of oral biofilms, commonly known as dental plaque. These biofilms are complex communities of microorganisms.
This bacterium contributes to a balanced oral environment by physically competing with and inhibiting the colonization of more harmful, pathogenic bacteria. It can produce hydrogen peroxide, which helps suppress the growth of other bacterial species. Streptococcus gordonii also creates an environment that can make it less hospitable for certain cavity-forming bacteria, such as Streptococcus mutans, by modulating the oral environment through mechanisms like the arginine deiminase pathway.
Its Association with Disease
Despite its beneficial contributions to oral health, Streptococcus gordonii can act as an opportunistic pathogen under certain circumstances. Its most recognized association with disease is infective endocarditis, an infection of the heart’s inner lining and valves. This bacterium can enter the bloodstream, for instance, during dental procedures that cause bleeding or oral trauma.
Once in the bloodstream, Streptococcus gordonii can adhere to damaged heart valves and form biofilms. The cell wall components of S. gordonii, such as serine-rich repeat adhesins, play a role in its ability to bind to platelets and erythrocytes, facilitating its spread to heart valves. This persistent exposure can lead to the development of infective endocarditis, a condition with a hospital mortality rate of approximately 20%.
Beyond infective endocarditis, Streptococcus gordonii can also be involved in other infections, particularly in immunocompromised individuals. It has been linked to apical periodontitis, an inflammation around the root of a tooth, and can penetrate into root canals and dentinal tubules, leading to inflammatory conditions. Less commonly, it has been implicated in systemic infections like septic arthritis, which causes joint inflammation and bone loss, and empyema, an accumulation of pus in the lungs.
Prevention and Management
Preventing infections caused by Streptococcus gordonii largely centers on maintaining good oral hygiene. Regular brushing twice daily with fluoride toothpaste and daily flossing helps manage oral biofilm (plaque) and reduces the bacterial load in the mouth. Consistent dental check-ups and professional cleanings are also important for removing accumulated plaque and addressing any developing oral health issues.
For individuals at an elevated risk of infective endocarditis, such as those with pre-existing heart conditions, healthcare professionals may advise prophylactic antibiotics before certain dental procedures. This preventative measure aims to reduce the number of bacteria entering the bloodstream during invasive dental work, thereby lowering the risk of infection. However, the guidelines for antibiotic prophylaxis have evolved, and their use is now more targeted to specific high-risk patient groups to mitigate concerns about antibiotic resistance.
If an infection caused by Streptococcus gordonii does occur, treatment typically involves antibiotic therapy. The specific antibiotic and duration of treatment are determined by the location and severity of the infection, often after identifying the bacteria through laboratory tests. In some cases, particularly for infective endocarditis, surgical intervention may also be necessary to remove infected tissue or repair damaged heart valves.