Species distribution and antifungal susceptibility of 358 Trichosporon clinical isolates collected in 24 medical centres.

OBJECTIVES: To provide species distribution and antifungal susceptibility profiles of 358 Trichosporon clinical isolates collected from 24 tertiary-care hospitals. METHODS: Species identification was performed by sequencing the IGS1 region of rDNA. Antifungal susceptibility testing for amphotericin B, fluconazole, voriconazole and posaconazole followed the Clinical and Laboratory Standards Institute reference method. Tentative epidemiologic cutoff values (97.5% ECVs) of antifungals for Trichosporon asahii were also calculated. RESULTS: Isolates were cultured mostly from urine (155/358, 43.3%) and blood (82/358, 23%) samples. Trichosporon asahii was the most common species (273/358, 76.3%), followed by T. inkin (35/358, 9.7%). Isolation of non-T. asahii species increased substantially over the last 11 years [11/77 (14.2%) from 1997 to 2007 vs. 74/281, (26.3%) from 2008 to 2018, p0.03]. Antifungal susceptibility testing showed high amphotericin B minimum inhibitory concentrations against Trichosporon isolates, with higher values for T. faecale. The ECV for amphotericin B and T. asahii was set at 4 µg/mL. Among the triazole derivatives, fluconazole was the least active drug. The ECVs for fluconazole and posaconazole against T. asahii were set at 8 and 0.5 µg/mL, respectively. Voriconazole showed the strongest in vitro activity against the Trichosporon isolates; its ECV for T. asahii was set at 0.25 µg/mL after 48 hours' incubation. CONCLUSIONS: Trichosporon species diversity has increased over the years in human samples, and antifungal susceptibility profiles were species specific. Trichosporon asahii antifungal ECVs were proposed, which may be helpful to guide antifungal therapy.

The Candida albicans AAA ATPase homologue of Saccharomyces cerevisiae Rix7p (YLL034c) is essential for proper morphology, biofilm formation and activity of secreted aspartyl proteinases.

Proper morphology is essential for the ability of Candida albicans to switch between yeast and hyphae and thereby sustain its virulence. Here we identified, by differential screening, a novel C. albicans AAA ATPase encoding gene, CaYLL34 (RIX7), with enhanced expression in hyphae. Phylogenetic analysis suggests that CaYLL34 belongs to a "VCP-like" subgroup of AAA ATPases essential for yeast viability and contains a bipartite nuclear localization signal. Inactivation of one copy of CaYLL34, by the URA-Blaster method, generated the heterozygous mutant strain M61. This strain has severe phenotypic alterations, such as a highly increased vacuole, abnormal cell shape and reduced growth in different conditions. Also, major pathogenicity factors are affected in M61, for instance, a significant decrease of hypha formation (>90%), surface biofilm adhesion (86%) and secreted aspartyl proteinase activity (76.5%). Our results show that the partial impairment of CaYll34p cellular levels is sufficient to affect the proper cellular morphology and pathogenicity factors and suggest that this protein is required for biogenesis of ribosomal subunits. Accordingly, we propose that the product of CaYLL34 could be tested as a novel target for antifungal drugs.

Prevalence rates and antifungal susceptibility profiles of the Candida parapsilosis species complex: results from a nationwide surveillance of candidaemia in Brazil.

The genetically heterogeneous taxon Candida parapsilosis was recently reclassified into three species: Candida parapsilosis, Candida orthopsilosis and Candida metapsilosis. The prevalences of these species among 141 bloodstream isolates tested in Brazil were 88% for C. parapsilosis, 9% for C. orthopsilosis, and 3% for C. metapsilosis. Except for three C. orthopsilosis isolates that were considered resistant to 5-flucytosine, all isolates representing the different species of this complex were susceptible to polyenes, triazoles and caspofungin.