Oral Microbiology and Immunology by Lamont Richard J.;Hajishengallis George;Koo Hyun;Jenkinson Howard F.;

Author:Lamont, Richard J.;Hajishengallis, George;Koo, Hyun;Jenkinson, Howard F.; [Неизв.]
Language: eng
Format: epub
Publisher: American Society for Microbiology Press (Textbook)

Commensal-Pathogen Interactions

Numerous bacterial species are recognized as commensal, as they are linked to the health status of the oral cavity and exhibit diverse protective properties that inhibit the initiation and development of dental caries. The inverse association between the abundance of oral commensal bacteria such as S. sanguinis and S. gordonii from the mitis group (associated with health) and that of S. mutans (linked with disease) has been documented, implying that mitis group streptococci may have the ability to control S. mutans growth and accumulation. Many streptococci from the mitis group produce copious amounts (in the millimolar range) of H2O2, which inhibits the growth of S. mutans and other cariogenic bacteria. Interestingly, peroxide also serves as a signaling molecule, and fine-tuned production regulates biofilm formation by commensal bacteria. Another interesting example of antagonistic interactions between commensal streptococci and S. mutans is that commensal bacteria may be able to hijack a host factor to become antagonistic against the pathogen. Specifically, host-derived nitrate and nitrite are highly enriched in the oral cavity, and high concentrations of nitrite have been associated with lower incidence of dental caries. It follows that H2O2 produced by commensal streptococci interacts with nitrite to form peroxynitrate, which is lethal to S. mutans, explaining why high levels of nitrite and commensal streptococci can predict low caries incidence. Other factors that can swing the competition between commensal streptococci and cariogenic streptococci are amino sugars. For example, compared to S. mutans, commensal streptococci are better equipped to utilize amino sugars such as N-acetylglucosamine and glucosamine. Such metabolic competition is partially achieved by the production of ammonia that serves to neutralize the intracellular pH. Overall, a better understanding of the complex metabolic interactions in oral bacteria will offer new opportunities to design and develop therapeutic strategies to prevent, arrest and treat dental caries.

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