Real-Time Approach to Flow Cell Imaging of Candida albicans Biofilm Development.

Andrew Mccall,Mira Edgerton

doi:10.3390/jof3010013

Abstract

The ability of Candida albicans to form biofilms is a virulence factor that allows tissue attachment and subsequent infection of host tissues. Fungal biofilms have been particularly well studied, however the vast majority of these studies have been conducted under static conditions. Oral biofilms form in the presence of salivary flow, therefore we developed a novel flow system used for real-time imaging of fungal biofilm development. C. albicans wild-type (WT) cells readily attached to the substrate surface during the 2 h attachment phase, then formed heterogeneous biofilms after 18 h flow. Quantitative values for biomass, rates of attachment and detachment, and cell–cell adhesion events were obtained for C. albicans WT cells and for a hyperfilamentous mutant Δhog1. Attachment rates of C. albicans WT cells were nearly 2-fold higher than C. albicans Δhog1 cells, although Δhog1 cells formed 4-fold higher biomass. The reduced normalized detachment rate was the primary factor responsible for the increased biomass of Δhog1 biofilm, showing that cell detachment rates are an important predictor for ultimate biofilm mass under flow. Unlike static biofilms, C. albicans cells under constant laminar flow undergo continuous detachment and seeding that may be more representative of the development of in vivo biofilms.

Highlights

Candida albicans is the most common source of oral and systemic fungal infections [1]
We found that biofilms formed in our flow system reproduced the mixed yeast, hyphae, and pseudohyphae layers of biofilms formed in catheter models, and developed microcolonies from single Candida albicans hyphal cells that are very similar phenotypically to the microcolonies formed upon invasion of epithelial monolayers [23]
We were able to develop a novel system to analyze in real-time the attachment and development of C. albicans biofilms under flow

Summary

Introduction

Candida albicans is the most common source of oral and systemic fungal infections [1]. Numerous in vitro studies have analyzed the growth and development of C. albicans biofilms on many surfaces, including acrylic, silicone, plastic, glass, and catheters [4,5,6,7] These studies have largely been carried out under static conditions in which the medium overlying the biofilm lacks flow. The average shear stress generated by saliva across a tooth surface has been calculated to be 0.8 dynes/cm2 [9] Despite this relatively low shear stress value; it is likely that salivary flow contributes to reduced formation of C. albicans biofilms, as patients with xerostomia (reduced salivary flow) are at increased risk of developing oral candidiasis [10,11]

Methods

Results

Conclusion