Polymicrobial interactions between Streptococcus mitis, Streptococcus sanguinis and oral associated Candida albicans on an in vitro salivary biofilm and differential expression of ALS1, ALS2 and ALS3 genes

Abstract

Interactions between oral microorganisms contribute to formation of polymicrobial communities on surfaces and prosthetics. Since streptococci are early colonizers, the ability of Candida albicans to adhere to streptococci paves the way for an additional surface for candidal colonization and propagation. This study aimed to investigate the molecular response of C. albicans to two species of streptococci, i.e. Streptococcus mitis and Streptococcus sanguinis in in vitro salivary biofilms. Single, dual and mixed species salivary biofilms were formed for 24 h. Biofilm biomass and cellular metabolic activity of microbial species were assessed by crystal violet (CV) staining and XTT reduction assay, respectively, followed by scanning electron microscopy. ALS1, ALS2 and ALS3 genes were screened and quantified using qPCR. CV and XTT analysis showed a significant increase in biofilm biomass and cellular metabolic activity of two dual species and mixed species in comparison to single species biofilm. SEM analysis revealed formation of candidal hyphae under influence of streptococci. ALS1 and ALS3 were significantly overexpressed in a mixed species biofilm, in comparison to dual species and single species biofilms. Presence of S. mitis and S. sanguinis assisted in the proliferation of C. albicans which may augment tissue invasion. This study proposes substantial contribution of bacteria in propagation of C. albicans biofilm. Hence, in oral fungal conditions, promotion of the infection may be contingent upon the bacterial constituent, a prospect which is frequently neglected and requires more research.

Keywords

• biofilm
• candida
• microbiology
• sem
• streptococcus
• oral associated
• polymicrobial biofilm