Ergosterol Pathway of Candida albicans Promotes the Growth and Cariogenic Virulence of Streptococcus mutans

  Objective   To investigate the effect of Candida albicans (C. albicans) on proliferation and virulence of Streptococcus mutans (S. mutans), and to verify the role of the ergosterol pathway in it.

  Methods  After single- and co-cultivation of C. albicans wild-type 5314 and S. mutans UA159, the absorbance value of OD₆₀₀ and colony-forming units (CFU) were detected to reflect the influence of C. albicans on the growth of S. mutans. To reflect the influence of C. albicans on the virulence of S. mutans, the production of extracellular polysaccharides was detected by anthrone-vitriol method, and the acid production capacity was detected by a pH meter. After single- and co-cultivation of C. albicans mutant strains and S. mutans, the growth of S. mutans was evaluated by CFU. After inhibiting the ergosterol pathway by 0 mg/L, 0.012 5 mg/L, and 0.025 mg/L fluconazole for 24 h, the CFU of single- and co-cultivated C. albicans wild-type and S. mutans were detected.

  Results  The OD₆₀₀ absorbance value and CFU in theco-cultivation of C. albicans wild-type and S. mutans was higher than that in the single culture (P<0.05), and the production of extracellular polysaccharides in S. mutans was increased when S. mutans was co-cultured with C. albicans (P<0.05), accompanied with a more obvious decrease of pH (P<0.05). Fourteen strains in whole 42 C. albicans mutant strains lost the growth-promoting effect on S. mutans, including 6 ergosterol synthesis-related mutant strains. After co-cultivation of the 6 ergosterol synthesis-related mutant strains and S. mutans, the CFU of S. mutans remained unchanged or decreased. After inhibiting the ergosterol pathway by 0.012 5 mg/L and 0.025 mg/L fluconazole, the CFU of S. mutans in the co-cultivation of C. albicans wild-type and S. mutans was lower than that without fluconazole treatment (P<0.05), while the CFU of C. albicans and S. mutans single-cultivations did not change significantly (P>0.05) and the CFU of C. albicans in the co-cultivation of C. albicans wild-type and S. mutans did not change significantly (P>0.05).

  Conclusion  C.albicans can enhance the growth ability and virulence of S. mutans through the ergosterol-related pathway. This process can be inhibited by fluconazole, which is expected to become a novel strategy to prevent and treat dental caries.