Microbial Pathogenesis of Oral OrganismsBING-YAN WANG, DMD, PhD personal profile
Streptococcus mutans is the primary cariogen that produces several virulence factors. It is also implicated in some cases of infective endocarditis. S. mutans competence-stimulating peptide (CSP, encoded by the comC gene) and a signal transduction system (a quorum sensing system encoded by the comD and comE genes) mediate a variety of virulence characteristics—biofilm formation, bacteriocin production, acid tolerance, antimicrobial sensitivity, and natural genetic transformation. Elimination of CSP or its signal transduction system by deletion of the comC, D, or E genes results in alterations in all of these virulence activities.
Other oral bacteria, such as the commensal early colonizing dental plaque species Streptococcus gordonii, can inactivate S. mutans CSP, thereby interfering with S. mutans bacteriocin production. Therefore, it is not merely colonization by S. mutans that determines the ultimate cariogenicity of plaque, but the interaction of the pathogen with other biofilm bacteria that affect virulence. Other bacteria present in dental plaque may modulate quorum sensing-dependent expression of virulence properties of the organism.
We are characterizing specific interactions of S. mutans with oral bacteria in the dental plaque biofilm. We will determine the effects of other early colonizers such as Actinomyces naeslundii and later anaerobic colonizers such as Porphyromonas gingivalis on quorum-sensing in S. mutan, and the effects of these organisms on the virulence-associated properties of S. mutans.
“The unique thing about our PhD program is that, in most cases, the graduate students are also clinical residents, so they get a unique exposure to both worlds.”