Variation in biofilm formation among blood and oral isolates of Candida albicans and Candida dubliniensis

Introduction: Biofilm production is considered a potential virulence factor of some Candida species. For this reason, an understanding of biofilm behavior of Candida albicans and its closely related species Candida dubliniensis is key to the development of effective preventive measures for invasive and oral candidiasis. The aim of this study was to compare the capacity of biofilm production by blood and oral isolates of C. albicans and C. dubliniensis using polystyrene, flat-bottomed 100-well microtiter plates.

Methods: A total of 47 isolates, consisting of 28 C. albicans (16 oral and 12 blood isolates) and 19 C. dubliniensis (11 oral and 8 blood isolates) were compared for their biofilm forming ability under aerobic and static conditions. XTT reduction assay was used to quantify the sessile growth.

Results: All tested isolates produced biofilm, measured as XTT metabolic activity. Biofilm formation by C. albicans isolates was statistically significantly higher than biofilm formation by C. dubliniensis isolates at 24h (P=0.03) and 48 h (P=0.0001). There was a higher percentage (41.7%) of high producers of biofilms among C. albicans blood isolates than among oral isolates (31.3%), without statistically significant differences.

Conclusions: This capability may allow C. albicans and C. dubliniensis to maintain their oral ecological niches as commensal or pathogenic microorganisms and can be a major virulence factor during invasive candidiasis. However, the differences in biofilm production among isolates should be taken into account when the anti-biofilm activity of antifungal agents or other virulence factors are tested in vitro.