Abstract
Streptococcus mutans and Candida albicans are found together in the oral biofilms on dental surfaces, but little is known about the ecological interactions between these species. Here, we studied the effects of S. mutans UA159 on the growth and pathogencity of C. albicans. Initially, the effects of S. mutans on the biofilm formation and morphogenesis of C. albicans were tested in vitro. Next, we investigate the influence of S. mutans on pathogenicity of C. albicans using in vivo host models, in which the experimental candidiasis was induced in G. mellonella larvae and analyzed by survival curves, C. albicans count in hemolymph, and quantification of hyphae in the host tissues. In all the tests, we evaluated the direct effects of S. mutans cells, as well as the indirect effects of the subproducts secreted by this microorganism using a bacterial culture filtrate. The in vitro analysis showed that S. mutans cells favored biofilm formation by C. albicans. However, a reduction in biofilm viable cells and inhibition of hyphal growth was observed when C. albicans was in contact with the S. mutans culture filtrate. In the in vivo study, injection of S. mutans cells or S. mutans culture filtrate into G. mellonella larvae infected with C. albicans increased the survival of these animals. Furthermore, a reduction in hyphal formation was observed in larval tissues when C. albicans was associated with S. mutans culture filtrate. These findings suggest that S. mutans can secrete subproducts capable to inhibit the biofilm formation, morphogenesis and pathogenicity of C. albicans, attenuating the experimental candidiasis in G. mellonella model.
Highlights
The oral cavity is colonized with different microbial species that are usually organized in biofilms adhered to a solid surface such as dental enamel, root surface, or dental implants
Analysis of the interaction between S. mutans and C. albicans in the in vitro model of biofilm formation showed a higher C. albicans count (CFU/mL) in the mixed biofilms formed by C. albicans and S. mutans cells compared to the single biofilms formed by C. albicans and phosphate-buffered saline (PBS) (Control group)
These results show that S. mutans supernatant can cause reduction of C. albicans viable cells (CFU/mL), but it is not enough to reduce the total biomass of C. albicans biofilm
Summary
The oral cavity is colonized with different microbial species that are usually organized in biofilms adhered to a solid surface such as dental enamel, root surface, or dental implants. An interesting characteristic of biofilms is the presence of a wide variety of microbial species and the interactions between these microorganisms [1,2,3]. Despite the abundant interactions between fungi and bacteria in the oral cavity, our knowledge of the mechanisms involved in PLOS ONE | DOI:10.1371/journal.pone.0150457. Streptococcus mutant Can Attenuate the Virulence of Candida albicans. The specific roles of this author is articulated in the ‘author contributions’ section Despite the abundant interactions between fungi and bacteria in the oral cavity, our knowledge of the mechanisms involved in PLOS ONE | DOI:10.1371/journal.pone.0150457 March 2, 2016
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