The effect of saliva or serum on Streptococcus mutans and Candida albicans colonization of hydroxylapatite beads

Several recent reports imply the possibility of cariogenicity of denture plaque containing Candida albicans. Hence the purpose of this study was to investigate the effects of salivary and serum pellicles on C. albicans and Streptococcus mutans colonization on hydroxylapatite beads. Methods: The colonization of three isolates of C. albicans and two isolates of S. mutans was examined by the use of a bioluminescent adenosine triphosphate (ATP) assay based on the firefly luciferase-luciferin system. Results: In the preliminary study, a good correlation was observed between the cell number and ATP amount of each isolate tested, and the results yielded a level of significance (P<0.001; Student's t-test), confirming the validity of this method. When the relative ATP content of the 48 h colonization of both isolates of S. mutans were compared, a saliva pellicle was significantly more effective in promoting bacterial colonization than either uncoated or serum pellicle (ANOVA; P<0.01). In contrast, in the case of colonization of C. albicans isolates, a serum pellicle was significantly more effective in promoting the colonization of C. albicans GDH 18 and GDH 19, than both uncoated specimens and saliva pellicle (ANOVA; P<0.01). Similar trends were observed with C. albicans GDH 16, though significant differences were not observed (ANOVA; P>0.05). Conclusion: The results suggest that the mechanism involved in fungal colonization on hydroxylapatite (HAP) should be different from that of mutans streptococci.