Zhenting Xiang
| Zhenting Xiang |
Zhenting Xiang1, Yuan Liu2, Hyun Koo1
1Orthodontics, University of Pennsylvania, School of Dental Medicine; 2Preventive & Restorative Sciences, University of Pennsylvania, School of Dental Medicine
Introduction
Candida albicans can interact with Streptococcus gordonii and Streptococcus mutans, modulating bacterial accumulation and virulence. In particular, the fungal presence can enhance S. mutans growth and biofilm cariogenicity under sugar-rich conditions. However, how C. albicans interacts with different streptococcal species within mixed-biofilms to enhance cariogenic potential remains unclear. Here, we aimed to elucidate the role of C. albicans in modulating streptococci growth and bacterial population shifts in an inter-species biofilm model as well as its impact on acidification and enamel demineralization.
Methods
An inter-species biofilm model was established using C. albicans, S. mutans and S. gordonii. The microbial shift between S. mutans and S. gordonii was determined in the presence or absence of C. albicans to examine the fungal impact on bacterial proportions under cariogenic (with sucrose) and non-cariogenic (without sucrose) conditions. High-resolution confocal imaging, biochemical/microbiological assays, and pH-drop measurements were employed to analyze the biofilms. In addition, the effects of biofilms on human tooth-enamel demineralization were assessed via quantitative transverse microradiography.
Results
We initially analyzed the characteristics of dual-species (S. mutans and S. gordonii) and three-species (S. mutans, S. gordonii and C. albicans) biofilms. Our data showed that the presence of C. albicans promoted S. mutans overgrowth and dominance within biofilms and enhanced the production of extracellular glucan-matrix, resulting in accumulation of more acidogenic biofilms (vs. dual-species). In addition, the inclusion of C. albicans increased both enamel mineral loss and demineralized lesion depth despite the presence of buffering saliva. Interestingly, biofilm treatment with an antifungal agent (nystatin), effectively inhibited C. albicans growth and its influence on streptococci population shifts, reducing enamel demineralization.
Conclusion
Our results demonstrated that C. albicans colonization favors the overgrowth of S. mutans and enhances acidogenic biofilm accumulation resulting in increased enamel demineralization, highlighting the importance of controlling the fungal influence on biofilm cariogenicity.