Candida‐streptococcal mucosal biofilms display distinct structural and virulence characteristics depending on growth conditions and hyphal morphotypes

This study evaluated structural and virulence characteristics of Candida‐streptococcal biofilms formed on moist or semidry mucosal surfaces, and tested the effects of nutrient availability and hyphal morphotype on dual‐species biofilms. Three‐dimensional models of the oral mucosa formed by immortalized keratinocytes on a fibroblast‐embedded collagenous matrix were used. Infections were carried out using Streptococcus oralis strain 34, in combination with a C. albicans wild‐type strain, or pseudohyphal‐forming mutant strains. Increased moisture promoted a homogeneous surface biofilm by C. albicans. Dual biofilms had a stratified structure, with streptococci growing in close contact to the mucosa and fungi growing on the bacterial surface. Under semi‐dry conditions, Candida formed localized foci of dense growth, which promoted focal growth of streptococci in mixed biofilms. Candida biofilm biovolume was greater under moist conditions, albeit with minimal tissue invasion, compared to semidry conditions. Supplementing the infection medium with nutrients under semidry conditions intensified growth, biofilm biovolume and tissue invasion/damage, without changing biofilm structure. Under these conditions, the pseudohyphal mutants and S. oralis formed defective superficial biofilms, with most bacteria in contact with the epithelial surface, below a pseudohyphal mass, resembling biofilms growing in moist environment. The presence of S. oralis promoted fungal invasion and ...

Source: Oral Microbiology and Immunology - February 1, 2015 Category: Microbiology Authors: Martinna M. Bertolini, Hongbin Xu, Takanori Sobue, Clarissa J. Nobile, Altair Cury, Anna Dongari‐Bagtzoglou Tags: Original Article Source Type: research