Interactions Between Candida albicans and Streptococcus mutans in the Oral Cavity

Abstract

The oral microbial communities are some of the most complex microbial floras in the human body. Occurrence of oral disease results from disturbance of the equilibrium of this ecosystem. Dental caries or tooth decay is the most common oral disease particularly in children characterized by irreversible destruction of the tooth structure. These processes are the result of interactions between the various microbial species embedded in the biofilm formed on tooth surface known as dental plaque. The bacterial species Streptococcus mutans has long been considered the etiologic agent of caries, however our in vitro findings demonstrated that S. mutans avidly adheres to C. albicans forming mixed biofilms on abiotic surfaces. As mucosal biofilms are implicated in a wide variety of infections, it is imperative that we understand the implications of the interactions between colonizing microbial species, as they co-exist on host tissue surfaces. To that end, in this project, we developed a clinically relevant mouse model of oral co-infection to investigate the interactions between C. albicans and S. mutans in a host. In this model, experimental animals were orally infected with C. albicans then they were exposed to S. mutans through drinking water, whereas control animals received S. mutans. Four days post infection with C. albicans, animals were euthanized and tongues and teeth were harvested and assessed for microbial burden as well as tissue histopathology analysis. The combined findings from the study demonstrated that in the presence of C. albicans, a significantly higher numbers of S. mutans were recovered from tongues and teeth of mice compared to mice infected with only S. mutans. Histopathology of tongue sections revealed massive invasion of tissue by the invasive C. albicans hyphae along with accumulation of large amounts of S. mutans. In contrast, in mice with S. mutans alone, minimal amount of S. mutans was seen adhering to the tongues. The combined findings from this study indicate a potential role for C. albicans in mediating cariogenic development via its physical interactions with S. mutans. Therefore, future studies should focus on developing novel therapeutic strategies geared towards prevention of adhesion receptors to block adhesive microbial reactions.