Susceptibility profile of a Brazilian yeast stock collection of Candida species isolated from subjects with Candida-associated denture stomatitis with or without diabetes

Objective: This study investigated the susceptibility of 198 clinical isolates of Candida species against caspofungin, amphotericin B, itraconazole, and fluconazole. Study Design: Suspensions of the microorganisms were spread on Roswell Park Memorial Institute (RPMI) agar plates. Etest strips were placed on the plates, and the minimal inhibitory concentration (MIC) was read after incubation (48 h at 37°C). Data were analyzed by a factorial analysis of variance and a 2 × 2 post hoc test (α = .05). Results: C glabrata showed the highest MIC values (P < .001) against caspofungin, itraconazole, and fluconazole. For amphotericin B, the MIC values of C tropicalis and C glabrata (P = .0521) were higher than those of C albicans (P < .001). Itraconazole was the least effective antifungal; 93.3% of the C glabrata isolates, 3.3% of the C albicans, and 1.3% of the C tropicalis were resistant. All microorganisms were susceptible to caspofungin and amphotericin B. Conclusions: Caspofungin and amphotericin B should be recommended as an effective alternative for the management of oral Candida infections when treatment with topical or other systemic drugs has definitely failed. © 2013 Elsevier Inc. All rights reserved.

Acid Lipase from Candida viswanathii: Production, Biochemical Properties, and Potential Application

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Taxonomic assessment and enzymes production by yeasts isolated from marine and terrestrial Antarctic samples

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Production, purification, and characterization of an extracellular acid protease from the marine Antarctic yeast Rhodotorula mucilaginosa L7

The production, purification, and characterization of an extracellular protease released by Rhodotorula mucilaginosa L7 were evaluated in this study. This strain was isolated from an Antarctic marine alga and previously selected among others based on the capacity to produce the highest extracellular proteolytic activity in preliminary tests. R. mucilaginosa L7 was grown in Saboraud-dextrose medium at 25 °C, and the cell growth, pH of the medium, extracellular protease production and the glucose and protein consumption were determined as a function of time. The protease was then purified, and the effects of pH, temperature, and salt concentration on the catalytic activity and enzyme stability were determined. Enzyme production started at the beginning of the exponential phase of growth and reached a maximum after 48 h, which was accompanied by a decrease in the pH as well as reductions of the protein and glucose concentrations in the medium. The purified protease presented optimal catalytic activity at pH 5.0 and 50 °C. Finally, the enzyme was stable in the presence of high concentrations of NaCl. These characteristics are of interest for future studies and may lead to potential biotechnological applications that require enzyme activity and stability under acidic conditions and/or high salt concentrations.

Study on the effects of near-future ocean acidification on marine yeasts: a microcosm approach

Marine yeasts play an important role in biodegradation and nutrient cycling and are often associated with marine flora and fauna. They show maximum growth at pH levels lower than present-day seawater pH. Thus, contrary to many other marine organisms, they may actually profit from ocean acidification. Hence, we conducted a microcosm study, incubating natural seawater from the North Sea at present-day pH (8.10) and two near-future pH levels (7.81 and 7.67). Yeasts were isolated from the initial seawater sample and after 2 and 4 weeks of incubation. Isolates were classified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and representative isolates were identified by partial sequencing of the large subunit rRNA gene. From the initial seawater sample, we predominantly isolated a yeast-like filamentous fungus related to Aureobasidium pullulans, Cryptococcus sp., Candida sake, and various cold-adapted yeasts. After incubation, we found more different yeast species at near-future pH levels than at present-day pH. Yeasts reacting to low pH were related to Leucosporidium scottii, Rhodotorula mucilaginosa, Cryptococcus sp., and Debaryomyces hansenii. Our results suggest that these yeasts will benefit from seawater pH reductions and give a first indication that the importance of yeasts will increase in a more acidic ocean.

Influence of iron deprivation and sub-inhibitory concentrations of antifungal antibiotics on surface antigens of candida albicans yeast cells

This study examined the effect of iron deprivation and sub-inhibitory concentrations of antifungal agents on yeast cell surface antigen recognition by antibodies from patients with Candida infections. Separation of cell wall surface proteins by sodium dodecyl-polyacrylamide gel electrophoresis (SDS-PAGE) and immunological detection by immunoblotting, revealed that antigenic profiles of yeasts were profoundly influenced by the growth environment. Cells grown under iron-depleted conditions expressed several iron-regulated proteins that were recognized by antibodies from patient sera. An attempt to characterize these proteins by lectin blotting with concanavalin A revealed that some could be glycoprotein in nature. Furthermore, these proteins which were located within cell walls and on yeast surfaces, were barely or not expressed in yeasts cultivated under iron-sufficient conditions. The magnitude and heterogeneity of human antibody responses to these iron-regulated proteins were dependent on the type of Candida infection, serum antibody class and yeast strain. Hydroxamate-type siderophores were also detected in supernatants of iron depleted yeast cultures. This evidence suggests that Candida albicans expresses iron-regulated proteins/glycoproteins in vitro which may play a role in siderophore-mediated iron uptake in Candida albicans. Sequential monitoring of IgG antibodies directed against yeast surface antigens during immunization of rabbits revealed that different antigens were recognized particularly during early and later stages of immunization in iron-depleted cells compared to iron-sufficient cells. In vitro and in vivo adherence studies demonstrated that growth phase, yeast strain and growth conditions affect adhesion mechanisms. In particular, growth under iron-depletion in the presence of sub-inhibitory concentrations of polyene and azole antifungals enhanced the hydrophobicity of C.albicans. Growth conditions also influenced MICs of antifungals, notably that of ketoconazole. Sub-inhibitory concentrations of amphotericin B and fluconazole had little effect on surface antigens, whereas nystatin induced profound changes in surface antigens of yeast cells. The effects of such drug concentrations on yeast cells coupled with host defence mechanisms may have a significant affect on the course of Candida infections.

Five new species of yeasts from fresh water and marine habitats in the Florida Everglades

Yeast populations in the Shark River Slough of the Florida Everglades, USA, were examined during a 3-year period (2002–2005) at six locations ranging from fresh water marshes to marine mangroves. Seventy-four described species (33 ascomycetes and 41 basidiomycetes) and an approximately equal number of undescribed species were isolated during the course of the investigation. Serious human pathogens, such as Candida tropicalis, were not observed, which indicates that their presence in coastal waters is due to sources of pollution. Some of the observed species were widespread throughout the fresh water and marine habitats, whereas others appeared to be habitat restricted. Species occurrence ranged from prevalent to rare. Five representative unknown species were selected for formal description. The five species comprise two ascomycetes: Candida sharkiensis sp. nov. (CBS 11368T) and Candida rhizophoriensis sp. nov. (CBS 11402T) (Saccharomycetales, Metschnikowiaceae), and three basidiomycetes: Rhodotorula cladiensis sp. nov. (CBS 10878T) in the Sakaguchia clade (Cystobasidiomycetes), Rhodotorula evergladiensis sp. nov. (CBS 10880T) in the Rhodosporidium toruloides clade (Microbotryomycetes, Sporidiobolales) and Cryptococcus mangaliensis sp. nov. (CBS 10870T) in the Bulleromyces clade (Agaricomycotina, Tremellales).

Fatores de virulência, resistência ao estresse osmótico e susceptibilidade de isolados de Candida tropicalis oriundos de ambiente costeiro do nordeste brasileiro

Several studies have been developed regarding health risks associated with the recreational use of beaches contaminated with domestic sewage. These wastes contain various microorganisms, including Candida tropicalis, etiologic agent of both superficial infections such as systemic, as well as indicator of fecal contamination for the environment. In this context, the objective of this study was to characterize C. tropicalis isolates from the sandy beach of Ponta Negra, Natal, Rio Grande do Norte, Brazil, regarding the expression of in vitro virulence factors, adaptation to osmotic stress and susceptibility to antifungal drugs. We analyzed 62 environmental isolates of C. tropicalis and observed a great variation between them for the various virulence factors evaluated. In general, environmental isolates were more adherent to CEBH than C. tropicalis ATCC13803 reference strain, besides the fact they were also highly biofilm producers. In relation to morphogenesis, most isolates presented wrinkled phenotype in Spider medium (34 isolates, 54.8 %). When assessing enzyme activity, most isolates had higher proteinase production than C. tropicalis ATCC13803 reference strain. In addition, 35 isolates (56.4 %) had high hemolytic activity (hemolysis index > 55). With regard to C. tropicalis resistance to osmotic stress, 85.4% of the isolates were able to grow in a liquid medium containing 15% sodium chloride, corroborating to high survival capacity described for this yeast at marine environment. Finally, with regard to sensitivity to antifungal drugs, it was observed high resistance to the azoles tested, with the occurrence of the "Low-high" phenomenon and similar effect to the paradoxical growth which occurs to the echinocandins. For the three azoles tested we verified that 15 strains were resistant (24.2 %). Some strains were also resistant to amphotericin B (14 isolates, 22.6 %), while all of them were sensitive for the echinocandins tested. Therefore, our results demonstrate that C. tropicalis isolated from the sand of northeast of Brazil can fully express virulence attributes and showed a high persistence capacity on the coastal environment, in addition of being significantly resistant to most applied antifungals in current clinical practice. This constitutes a potential health risk to visitors of this environment, especially immunocompromised individuals and those with extreme age range.

Candida duobushaemulonii: an emerging rare pathogenic yeast isolated from recurrent vulvovaginal candidiasis in Brazil

The aim of this study was to identify Candida species isolated from women diagnosed with recurrent vulvovaginal candidiasis (RVVC) and their partners; and to evaluate the fluconazole (FLZ) susceptibility of the isolates. In a period of six years, among 172 patients diagnosed with vulvovaginal candidiasis, 13 women that presented RVVC and their partners were selected for this investigation. The isolates were obtained using Chromagar Candida medium, the species identification was performed by phenotypic and molecular methods and FLZ susceptibility was evaluated by E-test. Among 26 strains we identified 14 Candida albicans , six Candida duobushaemulonii, four Candida glabrata , and two Candida tropicalis . Agreement of the isolated species occurred in 100% of the couples. FLZ low susceptibility was observed for all isolates of C. duobushaemulonii (minimal inhibitory concentration values from 8-> 64 μg/mL), two C. glabrata isolates were FLZ-resistant and all C. albicans and C. tropicalis isolates were FLZ-susceptible. This report emphasises the importance of accurate identification of the fungal agents by a reliable molecular technique in RVVC episodes besides the lower antifungal susceptibility profile of this rare pathogen C. duobushaemulonii to FLZ.

Enzymatic Biodiesel Synthesis From Yeast Oil Using Immobilized Recombinant Rhizopus Oryzae Lipase.

The recombinant Rhizopus oryzae lipase (1-3 positional selective), immobilized on Relizyme OD403, has been applied to the production of biodiesel using single cell oil from Candida sp. LEB-M3 growing on glycerol from biodiesel process. The composition of microbial oil is quite similar in terms of saponifiable lipids than olive oil, although with a higher amount of saturated fatty acids. The reaction was carried out in a solvent system, and n-hexane showed the best performance in terms of yield and easy recovery. The strategy selected for acyl acceptor addition was a stepwise methanol addition using crude and neutralized single cell oil, olive oil and oleic acid as substrates. A FAMEs yield of 40.6% was obtained with microbial oils lower than olive oil 54.3%. Finally in terms of stability, only a lost about 30% after 6 reutilizations were achieved.