Candida tropicalis biofilm formation and expression levels of the CTRG ALS-like genes in sessile cells.

Candida tropicalis is an emergent pathogen with a high rate of mortality associated with it; however, less is known about its pathogenic capacity. Biofilm formation (BF) has important clinical repercussions, and it begins with adherence to a substrate. The adherence capacity depends principally on the cell surface hydrophobicity (CSH) and, at a later stage, on specific adherence due to adhesins. The ALS family in C. tropicalis, implicated in adhesion and BF, is represented in several CTRG genes. In this study, we determined the biofilm-forming ability, the primary adherence, and the CSH of C. tropicalis, including six isolates from blood and seven from urine cultures. We also compared the expression of four CTRG ALS-like genes (CTRG_01028, CTRG_02293, CTRG_03786, and CTRG_03797) in sessile versus planktonic cells, selected for their possible contribution to BF. All the C. tropicalis strains were biofilm producers, related to its filamentation capacity; all the strains displayed a high adherence ability correlated to the CSH, and all the strains expressed the CTRG genes in both types of growth. Urine isolates present, although not significantly, higher CSH, adherence, and biofilm formation than blood isolates. This study reveals that three CTRG ALS-like genes-except CTRG_03797-were more upregulated in biofilm cells, although with a considerable variation in expression across the strains studied and between the CTRG genes. C. tropicalis present a high biofilm capacity, and the overexpression of several CTRG ALS-like genes in the sessile cells suggests a role by the course of the biofilm formation.

Antifungal and anti-biofilm activity of a new Spanish extract of propolis against Candida glabrata.

BACKGROUND: Resistance to traditional antifungal agents is a considerable health problem nowadays, aggravated by infectious processes related to biofilm formation, usually on implantable devices. Therefore, it is necessary to identify new antimicrobial molecules, such as natural products, to develop new therapeutic strategies to prevent and eradicate these infections. One promising product is propolis, a natural resin produced by honeybees with substances from various botanical sources, beeswax and salivary enzymes. The aim of this work was to study the effect of a new Spanish ethanolic extract of propolis (SEEP) on growth, cell surface hydrophobicity, adherence and biofilm formation of Candida glabrata, a yeast capable of achieving high levels of resistance to available anti-fungal agents. METHODS: The antifungal activity of SEEP was evaluated in the planktonic cells of 12 clinical isolates of C. glabrata. The minimum inhibitory concentration (MIC) of propolis was determined by quantifying visible growth inhibition by serial plate dilutions. The minimum fungicide concentration (MFC) was evaluated as the lowest concentration of propolis that produced a 95% decrease in cfu/mL, and is presented as MFC50 and MFC90, which corresponds to the minimum concentrations at which 50 and 90% of the C. glabrata isolates were inhibited, respectively. Influence on cell surface hydrophobicity (CSH) was determined by the method of microbial adhesion to hydrocarbons (MATH). The propolis effect on adhesion and biofilm formation was determined in microtiter plates by measurement of optical density (OD) and metabolic activity (XTT-assay) in the presence of sub-MIC concentrations of SEEP. RESULTS: SEEP had antifungal capacity against C. glabrata isolates, with a MIC50 of 0.2% (v/v) and an MFC50 of 0.4%, even in azole-resistant strains. SEEP did not have a clear effect on surface hydrophobicity and adhesion, but an inhibitory effect on biofilm formation was observed at subinhibitory concentrations (0.1 and 0.05%) with a significant decrease in biofilm metabolism. CONCLUSIONS: The novel Spanish ethanolic extract of propolis shows antifungal activity against C. glabrata, and decreases biofilm formation. These results suggest its possible use in the control of fungal infections associated with biofilms.

Candida orthopsilosis fungemias in a Spanish tertiary care hospital: incidence, epidemiology and antifungal susceptibility.

BACKGROUND: Few studies exist on prevalence of fungemia by Candida orthopsilosis, with variable results. AIMS: To study the incidence, epidemiology and antifungal susceptibility of C. orthopsilosis strains isolated from fungemias over two years at a tertiary hospital. METHODS: Candidemia episodes between June 2007 and June 2009 in a university hospital (Puerta del Mar, Cádiz, Spain) were studied. The strains initially identified as Candida parapsilosis were genotypically screened for C. parapsilosis sensu stricto, C. orthopsilosis and Candida metapsilosis, and their antifungal susceptibility was evaluated. RESULTS: In this period 52 cases of candidemia were documented. Of the 19 strains originally identified as C. parapsilosis, 13 were confirmed as C. parapsilosis sensu stricto and 6 as C. orthopsilosis. Of the 52 isolates, the most frequent species were Candida albicans (30.8%), C. parapsilosis sensu stricto (25%), C. orthopsilosis, Candida tropicalis and Candida glabrata in equal numbers (11.5%). C. orthopsilosis isolates were susceptible to amphotericin B, caspofungin, voriconazole and fluconazole, with no significant differences in MIC values with C. parapsilosis sensu stricto. The source of isolates of C. orthopsilosis were neonates (50%) and surgery (50%), and 100% were receiving parenteral nutrition; however C. parapsilosis sensu stricto was recovered primarily from patients over 50 years (69.2%) and 46.1% were receiving parenteral nutrition. CONCLUSIONS: These findings show that C. orthopsilosis should be considered as human pathogenic yeast and therefore its accurate identification is important. Despite our small sample size our study suggests that a displacement of some epidemiological characteristics previously attributed to C. parapsilosis to C. orthopsilosis may be possible.