Characteristics of biofilm formation by Candida tropicalis and antifungal resistance

Abstract

Candida tropicalis is a common species related to nosocomial candidemia and candiduria. Most Candida spp. infections are associated with biofilm formation on implanted medical devices or on host epithelial cell surfaces. Sessile cells display phenotypic traits dramatically different from those of their free-living, planktonic counterparts, such as increased resistance to antimicrobial agents and to host defenses. The characteristics of C. tropicalis biofilm formation in vitro are described. By an XTT-reduction assay, an increase in metabolic activity was observed up to 24 h of biofilm formation, and this activity showed a linear relationship with sessile cell density. Scanning electron microscopy was used to further characterize C. tropicalis biofilms. The initial adherence of yeast cells was followed by germination, microcolony formation, filamentation and maturation at 24-48 h. Mature biofilms consisted of a dense network of yeast cells and filamentous forms of C. tropicalis. Increased resistance of sessile cells against fluconazole and amphotericin B was also demonstrated. Real-time reverse transcription-PCR quantification showed that sessile cells overexpressed ERG11 (coding for lanosterol 14 alpha-demethylase) and MDR1 (coding for an efflux protein belonging to the major facilitator superfamily). These mechanisms may contribute to the fluconazole resistance of the C. tropicalis biofilm.

Susceptibility of clinical isolates of Candida to photodynamic effects of curcumin

“…In addition, the comparison made among the mean absorbance values (CV staining) found in control biofilms showed that C. albicans isolates were strong biofilm-forming strains, when compared with C. glabrata and C. tropicalis isolates (P < 0.05). Conversely, other investigations have found that C. tropicalis may have a similar ability to form biofilms when compared with C. albicans [38]. These different results probably reflect the different growth conditions, that is, culture medium and substrate, and physiological variations among the strains used in different investigations.…”

Molecular Identification, Antifungal Susceptibility Profile, and Biofilm Formation of Clinical and Environmental Rhodotorula Species Isolates

“…Biofilms formed on PVC strips were fixed overnight at 4°C with 4% formaldehyde plus 2% glutaraldehyde buffered at pH 7.2 with 0.1 M sodium cacodylate. After fixation, the samples were treated with 1% osmium tetroxide in cacodylate buffer for 1 h. Subsequently, the samples were treated with 1% tannic acid for 45 min, washed three times with distilled water for 15 min, and treated again with 1% osmium tetroxide in cacodylate buffer for 1 h. The samples were dehydrated with a graded series of ethanol washes, critical-point dried in CO 2 , coated with gold, and examined with a JEOL JSM-5300 scanning electron microscope (26).…”

Mixed biofilms formed by C. albicans and non-albicans species: a study of microbial interactions

“…It is most frequently isolated from candidiasis, mainly in patients confined to intensive care units, and has been associated with fluconazole resistance. 6 C. krusei is an emerging pathogen, described as a systemic pathogen in patients with compromised host resistance, such as those with acquired immunodeficiency syndrome (AIDS). 7 A major attribute of the Candida genus virulence is its ability to form surface-attached microbial communities known as biofilms.…”