Biofilms formed by Candida albicans bloodstream isolates display phenotypic and transcriptional heterogeneity that are associated with resistance and pathogenicity

Abstract

BackgroundCandida albicans infections have become increasingly recognised as being biofilm related. Recent studies have shown that there is a relationship between biofilm formation and poor clinical outcomes in patients infected with biofilm proficient strains. Here we have investigated a panel of clinical isolates in an attempt to evaluate their phenotypic and transcriptional properties in an attempt to differentiate and define levels of biofilm formation.ResultsBiofilm formation was shown to be heterogeneous; with isolates being defined as either high or low biofilm formers (LBF and HBF) based on different biomass quantification. These categories could also be differentiated using a cell surface hydrophobicity assay with 24 h biofilms. HBF isolates were more resistance to amphotericin B (AMB) treatment than LBF, but not voriconazole (VRZ). In a Galleria mellonella model of infection HBF mortality was significantly increased in comparison to LBF. Histological analysis of the HBF showed hyphal elements intertwined indicative of the biofilm phenotype. Transcriptional analysis of 23 genes implicated in biofilm formation showed no significant differential expression profiles between LBF and HBF, except for Cdr1 at 4 and 24 h. Cluster analysis showed similar patterns of expression for different functional classes of genes, though correlation analysis of the 4 h biofilms with overall biomass at 24 h showed that 7 genes were correlated with high levels of biofilm, including Als3, Eap1, Cph1, Sap5, Plb1, Cdr1 and Zap1.ConclusionsOur findings show that biofilm formation is variable amongst C. albicans isolates, and categorising isolates depending on this can be used to predict how pathogenic the isolate will behave clinically. We have shown that looking at individual genes in less informative than looking at multiple genes when trying to categorise isolates at LBF or HBF. These findings are important when developing biofilm-specific diagnostics as these could be used to predict how best to treat patients infected with C. albicans. Further studies are required to evaluate this clinically.

Comparison of Various Methods Used to Detect Biofilm Production of Candida Species

“…evaluated of late by other authors, which is time consuming and expensive [3,14]. Compared to these newer techniques, XTT reduction assay is least expensive [3].…”

Candida albicans biofilm heterogeneity does not influence denture stomatitis but strongly influences denture cleansing capacity

“…Absorbance was read spectrophotometrically at 570 nm and isolates were grouped based on their level of biomass distribution. Isolates that fell below the 1 st quartile (Q 1 , OD 570 = 0.382) were classed as low biofilm formers (LBF) and strains with a biomass greater than the 3 rd quartile (Q 3 , OD 570 = 1.192) were deemed as high biofilm formers (HBF), as described previously (10,11).…”

“…Untreated controls were included for comparison. Following treatment, biofilms were washed with PBS and standardised XTT and CV assays were carried out to assess biofilm metabolic activity and biomass, respectively, as described previously (11,26).…”

“…However, the details of such surface interactions are not yet fully understood (8,9). Moreover, this problem is further compounded by the fact that C. albicans biofilms are clinically heterogeneous, and this phenotype has been shown to negatively impact patient outcomes (10)(11)(12). Whether this clinical heterogeneity plays a role in the intra-oral denture environment remains to be determined, as the influence of denture surfaces and methods of decolonisation needs to be considered.…”

Assessment of aliphatic poly(ester-carbonate-urea-urethane)s potential as materials for biomedical application

“…The formation of pathogenic biofilms, especially by Candida species, requires initial surface adhesion and is one of the virulence factors that facilitate the colonization of medical devises [33,34]. Chronic and recurrent fungal infections, as well as bloodstream invasive candidiasis are a consequence of pathogenic biofilm formation [34,35].…”