Biofilms are colonies of microbial cells encased in a self-produced organic polymeric matrix and
represent a common mode of microbial growth. Microbes growing as biofilm are highly resistant to
commonly used antimicrobial drugs. We aimed to screen and characterize biofilm formation by
different isolates of Candida on removed intrauterine devices (IUDs), to perform experimental
biofilm formation with isolated strains, and to examine biofilm by the crystal violet and XTT
reduction assays and scanning electron microscopy (SEM). A total of 56 IUDs were examined for
biofilm formation using Sabouraud’s dextrose chloramphenicol agar. Suspected colonies were
identified by different methods. Antifungal susceptibility testing with fluconazole (FLU) and
amphotericin B for the isolated strains and in vitro experimental biofilm formation was carried out.
The biofilm was quantified by crystal violet, XTT reduction assay and SEM. Among the 56 IUDs
investigated, 26 were Candida positive (46.4 %). Candida albicans was recovered from 15
isolates. The biofilm MIC of FLU was increased 64 to 1000 times compared to the MIC for
planktonic cells. The XTT method results were dependent on the Candida species; biofilm
formation was highest in Candida krusei and Candida glabrata strains, followed by C. albicans
and Candida tropicalis. SEM of Candida biofilm revealed a heterogeneous thick biofilm with a
mixture of micro-organisms. The main conclusion from this study was non-albicans Candida
represents more than a half of the Candida biofilm. Better understanding of Candida biofilms may
lead to the development of novel therapeutic approaches for the treatment of fungal infections,
especially resistant ones among IUD users.