Wild and partially synanthropic bird yeast diversity, in vitro virulence, and antifungal susceptibility of Candida parapsilosis and Candida tropicalis strains isolated from feces

Yeast complexes in the fecal samples of wild (Dendrocopos major, Picus viridis) and partially synanthropic (Bombycilla garrulus, Garrulus glandarius, Pica pica, and Pyrrhula pyrrhula) birds were studied in a forest ecosystem during winter. A total of 18 yeast species were identified: 16 ascomycetes and two basidiomycetes belonging to five subphyla of fungi: Saccharomycotina (15), Pezizomycotina (1), Agaricomycotina (1), and Pucciniomycotina (1). Most yeast species were found in the fecal samples of P. pyrrhula (Candida parapsilosis, C. zeylanoides, Debaryomyces hansenii, Hanseniaspora uvarum, Metschnikowia pulcherrima, Meyerozyma carpophila, M. guilliermondii, Rhodotorula mucilaginosa); the lowest number of yeast species was observed in the feces of B. garrulus (C. parapsilosis, C. zeylanoides, Met. pulcherrima, and Rh. mucilaginosa). The opportunistic species of the genus Candida were found only in feces of partially synanthropic birds: C. parapsilosis was observed in the feces of B. garrulus, G. glandarius, P. pica, and P. pyrrhula; its relative abundance was 69.3%, 49.1%, 10.5%, and 1.1%, respectively; C. tropicalis was observed in the feces of P. pica and G. glandarius; its relative abundance was 54.6% and 7.1%, respectively. Strains of C. parapsilosis and C. tropicalis isolated from the feces of partially synanthropic birds were evaluated for their susceptibility to conventional antifungal agents (fluconazole, voriconazole, amphotericin B) and hydrolytic activity. A total of 160 strains were studied. Resistance to fluconazole was detected in 86.8% of C. parapsilosis strains and in 87% of C. tropicalis strains; resistance to voriconazole was detected in 71.7% of C. parapsilosis and in 66.7% of C. tropicalis strains, and the lowest percentage of resistant strains was detected to amphotericin B, 2.8% and 3.7% in C. parapsilosis and C. tropicalis strains, respectively. Multiresistance was detected in one strain of C. parapsilosis isolated from P. pica feces and in one strain of C. tropicalis isolated from G. glandarius feces. Phospholipase and hemolysin activities in the strains of C. parapsilosis were low (mean Pz values of 0.93 and 0.91, respectively); protease activity was moderate (mean Pz value of 0.53). The ability to produce hydrolytic enzymes was higher in the isolated strains of C. tropicalis. The mean Pz values of phospholipase and hemolysin activities were moderate (mean Pz values of 0.63 and 0.60, respectively), whereas protease activity was high (mean Pz value of 0.32). Thus, wild and partially synanthropic birds play an important role in disseminating of various yeast species. These yeasts can enter the topsoil via feces and contribute to the formation of allochthonous and uneven soil yeast diversity in natural ecosystems. In addition, partially synanthropic birds can be vectors of virulent strains of opportunistic Candida species from urban environments to natural biotopes.

The role of fruits as reservoirs for resistant and virulent strains of opportunistic yeasts

Strains of the Candida parapsilosis and Meyerozyma guilliermondii species complexes isolated from the internal tissues of 26 fruit species from 21 countries were evaluated for their susceptibility to conventional antifungal compounds (fluconazole, voriconazole, amphotericin B) and hydrolytic activity. A total of 144 strains were studied. Resistance to at least one of the antifungal compounds tested was found in 26.4% of the endophytic strains examined. Most of the strains were insensitive to fluconazole. Multiresistance was detected only in two strains of C. parapsilosis sensu stricto from tropical apples. Phospholipase production and proteolytic and hemolytic activities were significantly higher in endophytes from tropical fruits. Resistant and virulent strains of opportunistic yeasts can thus spread worldwide via purchased fruit, which can harm people with a weakened immune status and children whose immune systems are not yet fully developed.

Development of Echinocandin Resistance in Candida haemulonii: An Emergent, Widespread, and Opportunistic Fungal Pathogen

Echinocandins, used for the prevention and treatment of invasive fungal infections, have led to a rise in breakthrough infections caused by resistant Candida species. Among these species, those belonging to the Candida haemulonii complex are rare multidrug-resistant (MDR) yeasts that are frequently misidentified but have emerged as significant healthcare-associated pathogens causing invasive infections. The objectives of this study were to investigate the evolutionary pathways of echinocandin resistance in C. haemulonii by identifying mutations in the FKS1 gene and evaluating the impact of resistance on fitness. After subjecting a MDR clinical isolate of C. haemulonii (named Ch4) to direct selection using increasing caspofungin concentrations, we successfully obtained an isolate (designated Ch4'r) that exhibited a high level of resistance, with MIC values exceeding 16 mg/L for all tested echinocandin drugs (caspofungin, micafungin, and anidulafungin). Sequence analysis revealed a specific mutation in the resistant Ch4'r strain, leading to an arginine-histidine amino acid substitution (R1354H), occurring at the G4061A position of the HS2 region of the FKS1 gene. Compared to the wild-type strain, Ch4'r exhibited significantly reduced growth proliferation, biofilm formation capability, and phagocytosis ratio, indicating a decrease in fitness. Transmission electron microscopy analysis revealed alterations in cell wall components, with a notable increase in cell wall thickness. The resistant strain also exhibited higher amounts (2.5-fold) of chitin, a cell wall-located molecule, compared to the wild-type strain. Furthermore, the resistant strain demonstrated attenuated virulence in the Galleria mellonella larval model. The evolved strain Ch4'r maintained its resistance profile in vivo since the treatment with either caspofungin or micafungin did not improve larval survival or reduce the fungal load. Taken together, our findings suggest that the acquisition of pan-echinocandin resistance occurred rapidly after drug exposure and was associated with a significant fitness cost in C. haemulonii. This is particularly concerning as echinocandins are often the first-line treatment option for MDR Candida species.

Unveiling the Morphostructural Plasticity of Zoonotic Sporotrichosis Fungal Strains: Possible Implications for Sporothrix brasiliensis Virulence and Pathogenicity

Sporotrichosis is a fungal infection caused by Sporothrix species, with Sporothrix brasiliensis as a prevalent pathogen in Latin America. Despite its clinical importance, the virulence factors of S. brasiliensis and their impact on the pathogenesis of sporotrichosis are still poorly understood. This study evaluated the morphostructural plasticity of S. brasiliensis, a fungus that causes sporotrichosis. Three cell surface characteristics, namely cell surface hydrophobicity, Zeta potential, and conductance, were assessed. Biofilm formation was also analyzed, with measurements taken for biomass, extracellular matrix, and metabolic activity. In addition, other potential and poorly studied characteristics correlated with virulence such as lipid bodies, chitin, and cell size were evaluated. The results revealed that the major phenotsypic features associated with fungal virulence in the studied S. brasiliensis strains were chitin, lipid bodies, and conductance. The dendrogram clustered the strains based on their overall similarity in the production of these factors. Correlation analyses showed that hydrophobicity was strongly linked to the production of biomass and extracellular matrix, while there was a weaker association between Zeta potential and size, and lipid bodies and chitin. This study provides valuable insights into the virulence factors of S. brasiliensis and their potential role in the pathogenesis of sporotrichosis.

Yeast community succession in cow dung composting process

Yeast complexes in the composting process of cow dung prepared to fertilize the soil for growing vegetables and fruits were studied. The average abundance of yeasts changed during the four temperature stages of the composting process. The highest abundance of yeasts, 1.38 × 10⁴ cfu/g, was observed in the second stage of heating from 20 to 40 °C; the lowest was studied in the stage with the highest temperature (65 °C), 1.68 × 10³ cfu/g. A total of 19 yeast species were observed and identified: 11 ascomycetes and 8 basidiomycetes, belonging to five subphyla of Fungi: Saccharomycotina (10), Pezizomycotina (1), Agaricomycotina (5), Pucciniomycotina (2), and Ustilaginomycotina (1). The greatest diversity of yeasts was found in the initial (20 °C) and second (heating up to 40 °C) temperature stages of composting (Aureobasidium pullulans (yeast-like fungus), Candida parapsilosis, Candida saitoana, Candida santamariae, Candida tropicalis, Curvibasidium cygneicollum, Cutaneotrichosporon moniliforme, Debaryomyces fabryi, Debaryomyces hansenii, Filobasidium magnum, Kazachstania sp., Moesziomyces bullatus, Naganishia globosa, Papiliotrema flavescens, Rhodotorula mucilaginosa, Scheffersomyces insectosa, Torulaspora delbrueckii, Vanrija musci), and the lowest in the stage of maximum heating (65 °C) (C. parapsilosis, C. tropicalis, Cyberlindnera jadinii).The opportunistic yeasts C. parapsilosis and C. tropicalis were obtained not only in the initial, second and third temperature stages of the composting process, but also in mature compost in the final stage prepared for soil application. This study shows that the cow dung, used in the farm studied did not meet the microbiological safety criteria. The reduction of opportunistic yeast species was not achieved with the composting method used. The likelihood of these species entering agricultural products via compost and soil and developing as endophytes in the internal tissues of fruits is very high. Since some strains of opportunistic Candida species from cow dung exhibited virulent characteristics (they produced hydrolytic enzymes and were resistant to antifungal compounds), additional phenotypic and genetic studies of the compost strains and their comparison with clinical isolates should be pursued.

Cyclosporine Affects the Main Virulence Factors of Cryptococcus neoformans In Vitro

This study aimed to investigate the effects of cyclosporine on the morphology, cell wall structure, and secretion characteristics of Cryptococcus neoformans. The minimum inhibitory concentration (MIC) of cyclosporine was found to be 2 µM (2.4 µg/mL) for the H99 strain. Yeast cells treated with cyclosporine at half the MIC showed altered morphology, including irregular shapes and elongated projections, without an effect on cell metabolism. Cyclosporine treatment resulted in an 18-fold increase in chitin and an 8-fold increase in lipid bodies, demonstrating changes in the fungal cell wall structure. Cyclosporine also reduced cell body and polysaccharide capsule diameters, with a significant reduction in urease secretion in C. neoformans cultures. Additionally, the study showed that cyclosporine increased the viscosity of secreted polysaccharides and reduced the electronegativity and conductance of cells. The findings suggest that cyclosporine has significant effects on C. neoformans morphology, cell wall structure, and secretion, which could have implications for the development of new antifungal agents.

Hydrolytic Enzyme Production and Susceptibility to Antifungal Compounds of Opportunistic Candida parapsilosis Strains Isolated from Cucurbitaceae and Rosaceae Fruits

Endophytic yeast species were studied in the internal tissues of ripe cultivated vegetables and fruits. A total of 19 yeast species, 11 ascomycete species, and 8 basidiomycete species were observed in the internal tissues of all fruits examined. The opportunistic yeast Candida parapsilosis was present in all plants studied. Several virulence factors (production of hydrolytic enzymes and sensitivity to antifungal agents) were examined in all 107 isolates of C. parapsilosis from the internal tissues of fruits. The most virulent isolates were found in vegetables. C. parapsilosis is widespread in nature and is often isolated from a variety of non-human sources. It is frequently involved in invasive infections that seriously affect human health. This species poses a high risk to immunocompromised individuals, such as HIV patients and surgical patients or children whose immune systems are not sufficiently mature. Since virulent isolates of Candida parapsilosis have been found in vegetables and fruits; their raw consumption may not be safe. Finally, we emphasize the importance of ongoing phenotypic and genetic studies of endophytic isolates of Candida parapsilosis and their comparison with clinical isolates.

Molecular investigations on Candida glabrata clinical isolates for pharmacological targeting

Prevalence of drug resistant C. glabrata strains in hospitalized immune-compromised patients with invasive fungal infections has increased at an unexpected pace. This has greatly pushed researchers in identification of mutations/variations in clinical isolates for better assessment of the prevailing drug resistance trends and also for updating of antifungal therapy regime. In the present investigation, the clinical isolates of C. glabrata were comprehensively characterized at a molecular level using metabolic profiling and transcriptional expression analysis approaches in combination with biochemical, morphological and chemical profiling methods. Biochemically, significant variations in azole susceptibility, surface hydrophobicity, and oxidative stress generation were observed among the isolates as compared to wild-type. The ¹H NMR profiling identified 18 differential metabolites in clinical strains compared to wild-type and were classified into five categories, that include: sugars (7), amino acids and their derivatives (7), nitrogen bases (3) and coenzymes (1). Transcriptional analysis of selective metabolic and regulatory enzymes established that the major differences were found in cell membrane stress, carbohydrate metabolism, amino acid biosynthesis, ergosterol pathway and turnover of nitrogen bases. This detailed molecular level/metabolic fingerprint study is a useful approach for differentiating pathogenic/clinical isolates to that of wild-type. This study comprehensively delineated the differential cellular pathways at a molecular level that have been re-wired by the pathogenic clinical isolates for enhanced pathogenicity and virulence traits.

The clinical isolates of Candida glabrata were characterized and found to be different in terms of metabolic pathways that could be targeted for drug development.

The Threat Called Candida haemulonii Species Complex in Rio de Janeiro State, Brazil: Focus on Antifungal Resistance and Virulence Attributes

Although considered rare, the emergent Candida haemulonii species complex, formed by C. haemulonii sensu stricto (Ch), C. duobushaemulonii (Cd) and C. haemulonii var. vulnera (Chv), is highlighted due to its profile of increased resistance to the available antifungal drugs. In the present work, 25 clinical isolates, recovered from human infections during 2011–2020 and biochemically identified by automated system as C. haemulonii, were initially assessed by molecular methods (amplification and sequencing of ITS1-5.8S-ITS2 gene) for precise species identification. Subsequently, the antifungal susceptibility of planktonic cells, biofilm formation and susceptibility of biofilms to antifungal drugs and the secretion of key molecules, such as hydrolytic enzymes, hemolysins and siderophores, were evaluated by classical methodologies. Our results revealed that 7 (28%) isolates were molecularly identified as Ch, 7 (28%) as Chv and 11 (44%) as Cd. Sixteen (64%) fungal isolates were recovered from blood. Regarding the antifungal susceptibility test, the planktonic cells were resistant to (i) fluconazole (100% of Ch and Chv, and 72.7% of Cd isolates), itraconazole and voriconazole (85.7% of Ch and Chv, and 72.7% of Cd isolates); (ii) no breakpoints were defined for posaconazole, but high MICs were observed for 85.7% of Ch and Chv, and 72.7% of Cd isolates; (iii) all isolates were resistant to amphotericin B; and (iv) all isolates were susceptible to echinocandins (except for one isolate of Cd) and to flucytosine (except for two isolates of Cd). Biofilm is a well-known virulence and resistant structure in Candida species, including the C. haemulonii complex. Herein, we showed that all isolates were able to form viable biofilms over a polystyrene surface. Moreover, the mature biofilms formed by the C. haemulonii species complex presented a higher antifungal-resistant profile than their planktonic counterparts. Secreted molecules associated with virulence were also detected in our fungal collection: 100% of the isolates yielded aspartic proteases, hemolysins and siderophores as well as phospholipase (92%), esterase (80%), phytase (80%), and caseinase (76%) activities. Our results reinforce the multidrug resistance profile of the C. haemulonii species complex, including Brazilian clinical isolates, as well as their ability to produce important virulence attributes such as biofilms and different classes of hydrolytic enzymes, hemolysins and siderophores, which typically present a strain-dependent profile.

The Flo Adhesin Family

The first step in the infection of fungal pathogens in humans is the adhesion of the pathogen to host tissue cells or abiotic surfaces such as catheters and implants. One of the main players involved in this are the expressed cell wall adhesins. Here, we review the Flo adhesin family and their involvement in the adhesion of these yeasts during human infections. Firstly, we redefined the Flo adhesin family based on the domain architectures that are present in the Flo adhesins and their functions, and set up a new classification of Flo adhesins. Next, the structure, function, and adhesion mechanisms of the Flo adhesins whose structure has been solved are discussed in detail. Finally, we identified from Pfam database datamining yeasts that could express Flo adhesins and are encountered in human infections and their adhesin architectures. These yeasts are discussed in relation to their adhesion characteristics and involvement in infections.

A case-series of bloodstream infections caused by the Meyerozyma guilliermondii species complex at a reference center of oncology in Brazil

Bloodstream infections (BSI) caused by Candida species are the fourth cause of healthcare associated infections worldwide. Non-albicans Candida species emerged in the last decades as agents of serious diseases. In this study, clinical and microbiological aspects of six patients with BSI due to the Meyerozyma (Candida) guilliermondii species complex from an oncology reference center in Brazil, were evaluated. To describe demographic and clinical characteristics, medical records of the patients were reviewed. Molecular identification of the isolates was performed by ITS1-5.8S-ITS2 region sequencing. Antifungal susceptibility was evaluated by the EUCAST method and the minimal inhibitory concentrations (MIC) assessed according to the epidemiological cutoff values. Virulence associated phenotypes of the isolates were also studied. Ten isolates from the six patients were evaluated. Five of them were identified as Meyerozyma guilliermondii and the others as Meyerozyma caribbica. One patient was infected with two M. caribbica isolates with different genetic backgrounds. High MICs were observed for fluconazole and echinocandins. Non-wild type isolates to voriconazole appeared in one patient previously treated with this azole. Additionally, two patients survived, despite infected with non-wild type strains for fluconazole and treated with this drug. All isolates produced hemolysin, which was not associated with a poor prognosis, and none produced phospholipases. Aspartic proteases, phytase, and esterase were detected in a few isolates. This study shows the reduced antifungal susceptibility and a variable production of virulence-related enzymes by Meyerozyma spp. In addition, it highlights the poor prognosis of neutropenic patients with BSI caused by this emerging species complex.

LAY ABSTRACT

Our manuscript describes demographic, clinical and microbiological characteristics of patients with bloodstream infection by the Meyerozyma guilliermondii species complex at a reference center in oncology in Brazil.

Mechanism of the lethal effect of Riparin E against bacterial and yeast strains

Riparins are alkamides naturally found in the fruits of Aniba riparia (Nees) Mez, but currently synthetic molecules as Riparin E (Rip-E) can be obtained. Potential biological of Rip-E as schistosomicidal agent against Schistosoma mansoni worms, as well as against Staphylococcus aureus strains has already been described. However, the mechanism of action related to antimicrobial activity of Rip-E against bacterial or fungi species has not yet been reported. This study had as objective to evaluate the Rip-E antimicrobial activity against Gram-positive and Gram-negative bacteria, as well as against yeast species of clinical importance. Minimal inhibitory concentrations of the compound against bacterial and yeast strains were determined by microdilution method. To verify if a possible lethal effect caused by Rip-E were related to plasma membrane damage, microbial cells treated with Rip-E were stained with 7-aminoactinomycin D (7-AAD) and analyzed by flow cytometry. Rip-E showed a bactericide effect against Gram-positive species S. aureus and S. epidermidis, as well as, against Gram-negative species Escherichia coli and Salmonella enterica Typhimurium, but was inactive against Pseudomonas aeruginosa. Moreover, Rip-E showed activity against fungi species Candida albicans and C. tropicalis. S. aureus, E. coli and C. albicans cells treated with Rip-E were marked with 7-aminoactinomycin D (7-AAD) indicating that Rip-E can cause plasma membrane damage, acting as a potential microbicide agent for prevention or treatment of infectious diseases.

Virulence of Clinical Candida Isolates

The factors enabling Candida spp. infections are secretion of hydrolytic enzymes, adherence to surfaces, biofilm formation or morphological transition, and fitness attributes. The aim of this study was to investigate the correlation between known extracellular virulence factors and survival of Galleria mellonella larvae infected with clinical Candida. The 25 isolates were tested and the activity of proteinases among 24/24, phospholipases among 7/22, esterases among 14/23, hemolysins among 18/24, and biofilm formation ability among 18/25 isolates was confirmed. Pathogenicity investigation using G. mellonella larvae as host model demonstrated that C. albicans isolates and C. glabrata isolate were the most virulent and C. krusei isolates were avirulent. C. parapsilosis virulence was identified as varied, C. inconspicua were moderately virulent, and one C. palmioleophila isolate was of low virulence and the remaining isolates of this species were moderately virulent. According to our study, virulence of Candida isolates is related to the expression of proteases, hemolysins, and esterases.

The serine peptidase inhibitor N-ρ-tosyl-l-phenylalanine chloromethyl ketone (TPCK) affects the cell biology of Candida haemulonii species complex

Candida haemulonii species complex (C. haemulonii, C. haemulonii var. vulnera and Candida duobushaemulonii) is composed by emerging and multidrug-resistant (MDR) yeasts. Candidiasis, the disease caused by these species, is difficult to treat and culminates in clinical failures and patient death. It is well-known that Candida peptidases play important roles in the fungus-host interactions, and hence these enzymes are promising targets for developing new antifungal drugs. Recently, serine-type peptidases were described in clinical isolates of C. haemulonii complex with the ability to cleave relevant key host proteins. Herein, the effects of serine peptidase inhibitors (SPIs) on the cell biology of this fungal complex were evaluated. Initially, eight distinct SPIs (phenylmethylsulfonyl fluoride - PMSF, 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride - AEBSF, N-α-tosyl-l-lysine chloromethyl ketone hydrochloride - TLCK, N-p-tosyl-l-phenylalanine chloromethyl ketone - TPCK, simeprevir, boceprevir, danoprevir and telaprevir) were tested on the fungal growth. TPCK showed the best efficacy in controlling cell proliferation, being selected for the following experiments. This SPI induced changes in the architecture of yeast cells, as observed by scanning electron microscopy, besides injuries at the plasma membrane and reduction in the ergosterol content. TPCK also diminished the ability of yeasts to adhere to abiotic (polystyrene and glass) and biotic (murine macrophages) surfaces in a typically concentration-dependent manner. In addition, the 24 h-treatment of the mature biofilm promoted a decrease in biomass, viability and extracellular matrix. Altogether, our results highlight that SPIs may be promising new therapeutic agents in the treatment of candidiasis caused by emergent, opportunistic and MDR species forming the C. haemulonii complex.

Secreted aspartyl peptidases by the emerging, opportunistic and multidrug-resistant fungal pathogens comprising the Candida haemulonii complex

The opportunistic pathogens comprising the Candida haemulonii complex (C. haemulonii, C. duobushaemulonii and C. haemulonii var. vulnera) are notable for their intrinsic resistance to different antifungal classes. Little is known about the virulence attributes in this emerging fungal complex. However, it is well-recognized that enzymes play important roles in virulence/pathogenesis of candidiasis. Herein, we aimed to identify aspartyl-type peptidases in 12 clinical isolates belonging to the C. haemulonii complex. All isolates were able to grow in a chemically defined medium containing albumin as the sole nitrogen source, and a considerable consumption of this protein occurred after 72-96 h. C. haemulonii var. vulnera isolates showed the lowest albumin degradation capability and the poorest growth rate. The measurement of secreted aspartyl peptidase (Sap) activity, using the cathepsin D fluorogenic substrate, varied from 91.6 to 413.3 arbitrary units and the classic aspartyl peptidase inhibitor, pepstatin A, significantly blocked the Sap released by C. haemulonii complex. No differences were observed in the Sap activity among the three fungal species. Flow cytometry, using a polyclonal antibody against Sap1-3 of C. albicans, detected homologous proteins at the surface of C. haemulonii complex (anti-Sap1-3-labeled cells ranged from 24.6 to 79.1%). Additionally, the immunoblotting assay, conducted with the same Sap1-3 antibody, recognized a protein of ∼50 kDa in all fungal isolates. A glimpse in the genome of these fungi revealed several potential proteins containing Sap1-3-like conserved domain. Altogether, our results demonstrated the potential of C. haemulonii species complex to produce Saps, an important virulence factor of Candida spp.

Comparative Analysis of Putative Virulence-Associated Factors of Microsporum canis Isolates from Human and Animal Patients

Microsporum canis is a zoophilic dermatophyte and the most common fungus isolated from dogs and cats worldwide. To invade skin, this pathogen uses different enzymes, which may be associated with virulence, that contribute to the fungal pathogenicity. The aim of this study is to compare the expression of enzymes that may be associated with virulence, and thermotolerance of M. canis strains isolated from dogs, cats, and humans. The in vitro expression of the enzymes keratinase, catalase, urease, hemolysin, and aspartic protease was evaluated in 52 M. canis strains recently isolated from 14 human patients, 12 dogs, 15 symptomatic, and 11 asymptomatic cats. In addition, thermotolerance was assessed by comparative analysis of fungal growth at 25 °C and 35 °C. Keratinase activity was low in 34 and moderate in 18 strains. Aspartic-protease activity was low in 7, moderate in 33, and high in 12 strains. Hemolysin activity was low in 44 and moderate in 8 strains. All strains were classified as low producers of catalase. All but three strains produced urease in vitro, with a broad range of activity. The strains presented in vitro growth at the two studied temperatures were classified as presenting low (36.5%), medium (44.3%), or high (19.2%) thermotolerance. There was no statistically significant difference in the new putative virulence-associated factors studied among the different hosts, which suggests that they may have a similar role on human, cat, and dog infection. Also, no difference was observed between strains isolated from symptomatic and asymptomatic cats. This suggests that these factors have a limited impact on the fate of feline dermatophytosis caused by M. canis.

Biofilm Formed by Candida haemulonii Species Complex: Structural Analysis and Extracellular Matrix Composition

Candida haemulonii species complex (C. haemulonii, C. duobushaemulonii, and C. haemulonii var. vulnera) has emerged as opportunistic, multidrug-resistant yeasts able to cause fungemia. Previously, we showed that C. haemulonii complex formed biofilm on polystyrene. Biofilm is a well-known virulence attribute of Candida spp. directly associated with drug resistance. In the present study, the architecture and the main extracellular matrix (ECM) components forming the biofilm over polystyrene were investigated in clinical isolates of the C. haemulonii complex. We also evaluated the ability of these fungi to form biofilm on catheters used in medical arena. The results revealed that all fungi formed biofilms on polystyrene after 48 h at 37 °C. Microscopic analyses demonstrated a dense network of yeasts forming the biofilm structure, with water channels and ECM. Regarding ECM, proteins and carbohydrates were the main components, followed by nucleic acids and sterols. Mature biofilms were also detected on late bladder (siliconized latex), nasoenteric (polyurethane), and nasogastric (polyvinyl chloride) catheters, with the biomasses being significantly greater than on polystyrene. Collectively, our results demonstrated the ability of the C. haemulonii species complex to form biofilm on different types of inert surfaces, which is an incontestable virulence attribute associated with devices-related candidemia in hospitalized individuals.

In vitro characterization of virulence factors among species of the Candida parapsilosis complex

INTRODUCTION

Candida parapsilosis complex species differ from each other with regard to their prevalence and virulence.

METHODS

The hydrolytic enzyme activity, biofilm production, and adhesion to epithelial cells were analyzed in 87 C. parapsilosis complex strains.

RESULTS

Among the studied isolates, 97.7%, 63.2%, and 82.8% exhibited very strong proteinase, esterase, and hemolysin activity, respectively. All the C. parapsilosis complex isolates produced biofilms and presented an average adherence of 96.0 yeasts/100 epithelial cells.

CONCLUSIONS

Our results show that Candida parapsilosis complex isolates showed different levels of enzyme activity, biofilm production, and adhesion to epithelial cells.

Surface, adhesiveness and virulence aspects of Candida haemulonii species complex

The emerging opportunistic pathogens comprising the Candida haemulonii complex (C. haemulonii [Ch], C. duobushaemulonii [Cd] and C. haemulonii var. vulnera[Chv]) are notable for their intrinsic antifungal resistance. Different clinical manifestations are associated with these fungal infections; however, little is known about their biology and potential virulence attributes. Herein, we evaluated some surface properties of 12 clinical isolates of Ch (n = 5), Cd (n = 4) and Chv (n = 3) as well as their virulence on murine macrophages and Galleria mellonella larvae. Scanning electron microscopy demonstrated the presence of homogeneous populations among the species of the C. haemulonii complex, represented by oval yeasts with surface irregularities able to form aggregates. Cell surface hydrophobicity was isolate-specific, exhibiting high (16.7%), moderate (25.0%) and low (58.3%) hydrophobicity. The isolates had negative surface charge, except for one. Mannose/glucose- and N-acetylglucosamine-containing glycoconjugates were evidenced in considerable amounts in all isolates; however, the surface expression of sialic acid was poorly detected. Cd isolates presented significantly higher amounts of chitin than Ch and Chv. Membrane sterol and lipid bodies, containing neutral lipids, were quite similar among all fungi studied. All isolates adhered to inert surfaces in the order: polystyrene > poly-L-lysine-coated glass > glass. Likewise, they interacted with murine macrophages in a quite similar way. Regarding in vivo virulence, the C. haemulonii species complex were able to kill at least 80% of the larvae after 120 hours. Our results evidenced the ability of C. haemulonii complex to produce potential surface-related virulence attributes, key components that actively participate in the infection process described in Candida spp.

The serine peptidase inhibitor TPCK induces several morphophysiological changes in the opportunistic fungal pathogen Candida parapsilosis sensu stricto

Candida parapsilosis sensu stricto (C. parapsilosis) has emerged as the second/third commonest Candida species isolated from hospitals worldwide. Candida spp. possess numerous virulence attributes, including peptidases that play multiple roles in both physiological and pathological events. So, fungal peptidases are valid targets for new drugs development. With this premise in mind, we have evaluated the effect of serine peptidase inhibitors (SPIs) on both cell biology and virulence aspects of C. parapsilosis. First, five different SPIs, phenylmethylsulfonyl fluoride, benzamidine, 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride, N-α-tosyl-L-lysine chloromethyl ketone hydrochloride, and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) were tested, and TPCK showed the best efficacy to arrest fungal growth. Subsequently, the ability of TPCK to modulate physiopathological processes was investigated. Overall, TPCK was able to (i) inhibit the cell-associated serine peptidase activities, (ii) promote morphometric and ultrastructural alterations, (iii) induce an increase in the intracellular oxidation level, which culminates in a vigorous lipid peroxidation and accumulation of neutral lipids in cytoplasmic inclusions, (iv) modulate the expression/exposition of surface structures, such as mannose/glucose-rich glycoconjugates, N-acetylglucosamine-containing molecules, chitin, polypeptides and surface aspartic peptidases, (v) reduce the adhesion to either polystyrene or glass surfaces as well as to partially disarticulate the mature biofilm, (vi) block the fungal interaction with macrophages, and (vii) protect Galleria mellonella from fungal infection, enhancing larvae survivability. Altogether, these results demonstrated that TPCK induced several changes over fungal biology besides the interference with aspects associated to C. parapsilosis virulence and pathogenesis, which indicates that SPIs could be novel promising therapeutic agents in dealing with candidiasis.

Virulence of Candida haemulonii complex in Galleria mellonella and efficacy of classical antifungal drugs: a comparative study with other clinically relevant non-albicans Candida species

Candida haemulonii complex has emerged as notorious yeasts causing invasive infections with high rates of treatment failures. Since there is a particular interest in the development of non-mammalian host models to study microbial virulence, with the aim to evade the ethical impact of animal tests, herein we compared the virulence of C. haemulonii, C. duobushaemulonii and C. haemulonii var. vulnera with non-albicans Candida species (C. tropicalis, C. krusei and C. lusitaniae) on Galleria mellonella and the efficacy of antifungal drugs. All these fungi induced a dose-dependent effect on larvae killing, a decrease in hemocyte density and fungi were phagocytozed by hemocytes in equal proportions. Fungal inoculation caused early larvae melanization after some minutes of injection, followed by an augmented pigmentation after 24 h. Differences among species virulence can be explained, in part, by differences in growth rate and production of hydrolytic enzymes. First-line antifungals were tested with equivalent therapeutic doses and MIC profile in vitro was correlated with in vivo antifungal efficacy. Additionally, fungal burden increased in infected larvae along time and only caspofungin reduced the number of CFUs of C. haemulonii species complex. So, G. mellonella offers a simple and feasible model to study C. haemulonii complex virulence and drug efficacy.

Virulence properties and sensitivity profile of Candida parapsilosis complex species and Kodamaea ohmeri isolates from onychomycosis of HIV/AIDS patients

Cutaneous fungal infections include onychomycosis, an infection of the nail that affects both healthy and immunocompromised patients. This study investigated the in vitro hydrolytic enzymes production, adhesion and biofilm formation capacity of Candida parapsilosis complex species and Kodamaea ohmeri isolates from onychomycoses of HIV/AIDS patients and also established the antifungal sensitivity profiles of these isolates. Onychomycosis in HIV/AIDS patients showed a high prevalence of emerging yeasts, among which C. parapsilosis complex species and K. ohmeri were the most frequent. Three C. parapsilosis sensu stricto and two C. orthopsilosis isolates were resistant to amphotericin B and 83% of isolates were resistant to terbinafine. All three different species evaluated were proteinase and hemolysin producers. All isolates adhered to stainless steel and siliconized latex surfaces, and carbohydrates intensified adhesion of all isolates. Isolates adhered to keratinous nail and 50% formed biofilms with strong intensity. In multispecies or polymicrobial biofilms, C. albicans and Staphylococcus aureus regulated the biofilm formation of the analyzed species, decreasing the number of their cells in biofilms. The isolation of emerging yeast species from onychomycosis which are great producers of hydrolytic enzymes and with high adhesion and biofilm formation capacity is a result that should be considered relevant in clinical practice. In addition, half of the isolates was resistant to at least one of the tested antifungals. Taken together these data corroborate the infectious capacity and viability of these isolates under favorable conditions.

Antifungal effects of the flavonoids kaempferol and quercetin: a possible alternative for the control of fungal biofilms

This study aimed to determine the minimum inhibitory concentration (MIC) of kaempferol and quercetin against planktonic and biofilm forms of the Candida parapsilosis complex. Initially, nine C. parapsilosis sensu stricto, nine C. orthopsilosis and nine C. metapsilosis strains were used. Planktonic susceptibility to kaempferol and quercetin was assessed. Growing and mature biofilms were then exposed to the flavonoids at MIC or 10xMIC, respectively, and theywere also analyzed by confocal laser scanning microscopy. The MIC ranges were 32-128 µg ml^-1 for kaempferol and 0.5-16 µg ml^-1 for quercetin. Kaempferol and quercetin decreased (P < 0.05) the metabolic activity and biomass of growing biofilms of the C. parapsilosis complex. As for mature biofilms, the metabolic effects of the flavonoids varied, according to the cryptic species, but kaempferol caused an overall reduction in biofilm biomass. Microscopic analyses showed restructuring of biofilms after flavonoid exposure. These results highlight the potential use of these compounds as sustainable resources for the control of fungal biofilms.

Candida parapsilosis: from Genes to the Bedside

Patients with suppressed immunity are at the highest risk for hospital-acquired infections. Among these, invasive candidiasis is the most prevalent systemic fungal nosocomial infection. Over recent decades, the combined prevalence of non-albicans Candida species outranked Candida albicans infections in several geographical regions worldwide, highlighting the need to understand their pathobiology in order to develop effective treatment and to prevent future outbreaks. Candida parapsilosis is the second or third most frequently isolated Candida species from patients. Besides being highly prevalent, its biology differs markedly from that of C. albicans, which may be associated with C. parapsilosis' increased incidence. Differences in virulence, regulatory and antifungal drug resistance mechanisms, and the patient groups at risk indicate that conclusions drawn from C. albicans pathobiology cannot be simply extrapolated to C. parapsilosis Such species-specific characteristics may also influence their recognition and elimination by the host and the efficacy of antifungal drugs. Due to the availability of high-throughput, state-of-the-art experimental tools and molecular genetic methods adapted to C. parapsilosis, genome and transcriptome studies are now available that greatly contribute to our understanding of what makes this species a threat. In this review, we summarize 10 years of findings on C. parapsilosis pathogenesis, including the species' genetic properties, transcriptome studies, host responses, and molecular mechanisms of virulence. Antifungal susceptibility studies and clinician perspectives are discussed. We also present regional incidence reports in order to provide an updated worldwide epidemiology summary.

Exposure of Candida parapsilosis complex to agricultural azoles: An overview of the role of environmental determinants for the development of resistance

This work investigated the phenotypic behavior of Candida parapsilosis species complex in response to exposure to agricultural azoles and fluconazole. Three fluconazole-susceptible strains of C. parapsilosis sensu stricto, C. orthopsilosis and C. metapsilosis were used. Initial minimum inhibitory concentrations (iMICs) for agricultural and clinical azoles were determined by broth microdilution. Then, the strains were exposed to tebuconazole, tetraconazole and fluconazole for 15 days, at concentrations that were two-folded daily, starting at one-eighth the iMIC (iMIC/8) up to 64 times iMIC (64xiMIC). After 15-day-exposure, antifungal susceptibility, biofilm formation, CDR, MDR and ERG expression were evaluated. The three cryptic species developed tolerance to the antifungals they were exposed and presented reduction (P < 0.05) in fluconazole susceptibility. In addition, C. parapsilosis sensu stricto and C. metapsilosis also presented reduced susceptibility to voriconazole, after fluconazole exposure. Azole exposure decreased (P < 0.05) biofilm production by C. parapsilosis sensu stricto and C. orthopsilosis and increased (P < 0.05) the expression of ERG11 in all tested strains. The results show that exposure to agricultural azoles and fluconazole induces changes in the phenotypic behavior and gene expression by the three cryptic species of C. parapsilosis complex, highlighting the importance of environmental determinants for the development of antifungal resistance.

Surface properties, adhesion and biofilm formation on different surfaces by Scedosporium spp. and Lomentospora prolificans

In the present work, some surface properties of the fungi Scedosporium apiospermum, S. aurantiacum, S. minutisporum, and Lomentospora prolificans and their capability to adhere to and form a biofilm on diverse surfaces were evaluated. All four species had high conidial surface hydrophobicity and elevated electronegative zeta potentials. Abundant quantities of melanin were detected at the conidial surface, whereas sialic acid was absent. The numbers of non-germinated and germinated conidia adhered to poly-L-lysine-covered slides was higher than on glass after 4 h of fungi-surface contact. Additionally, after 72 h of interaction a typical biofilm structure had formed. Mature biofilms were also observed after 72 h on a nasogastric catheter (made from polyvinyl chloride), a late bladder catheter (siliconized latex), and a nasoenteric catheter (polyurethane). Interestingly, biofilm biomass increased considerably when the catheters had previously been incubated with serum. These results confirm that Scedosporium/Lomentospora spp. are capable of forming biofilms on diverse abiotic surfaces.

Antifungal susceptibility and virulence of Candida parapsilosis species complex: an overview of their pathogenic potential

PURPOSE

Antifungal resistance and several putative virulence factors have been associated with the pathogenicity of the Candida parapsilosis species complex. The objective of this study was to evaluate the antifungal susceptibility, the production of virulence factors and the pathogenicity of the C. parapsilosis complex.

METHODOLOGY

Overall, 49 isolates of C. parapsilosis sensu stricto, 19 C. orthopsilosis and nine C. metapsilosis were used. The planktonic and biofilm susceptibility to fluconazole, itraconazole, voriconazole, amphotericin B and caspofungin was assessed using a broth microdilution assay. Finally, the production of biofilm and hydrolytic enzymes and the fungal pathogenicity against Caenorhabditis elegans were investigated.Results/Key findings. Overall, one C. orthopsilosis was resistant to caspofungin and susceptible-dose-dependent to itraconazole, the other two C. orthopsilosis were susceptible-dose-dependent to fluconazole and itraconazole, and one C. metapsilosis was susceptible-dose-dependent to azoles. A total of 67.5 % of the isolates were biofilm producers. Amphotericin B and caspofungin caused the greatest reduction in the metabolic activity and biomass of mature biofilms. Phospholipase and protease production was observed in 55.1 % of C. parapsilosis sensu stricto, 42.1 % of C. orthopsilosis and 33.3 % of C. metapsilosis isolates. Moreover, 57.9 % of C. orthopsilosis and 20.4 % of C. parapsilosis sensu stricto isolates were β-haemolytic, and all C. metapsilosis were α-haemolytic. Finally, the C. parapsilosis complex caused high mortality of C. elegans after 96 h of exposure.

CONCLUSION

These results reinforce the heterogeneity of these cryptic species for their antifungal susceptibility, virulence and pathogenic potential, emphasizing the relevance of monitoring these emerging pathogens.

How much do we know about hemolytic capability of pathogenic Candida species?

Hemolytic factor production by pathogenic Candida species is considered an important attribute in promoting survival within the mammal host through the ability to assimilate iron from the hemoglobin-heme group. Hemolytic capability has been evaluated for Candida species based on hemolysis zones on plate assay, analysis of hemolytic activity in liquid culture medium, and hemolysis from cell-free culture broth. The production of hemolytic factor is variable among Candida species, where C. parapsilosis is the less hemolytic species. In general, no intraspecies differences in beta-hemolytic activities are found among isolates belonging to C. albicans, C. glabrata, C. krusei, C. tropicalis, and C. parapsilosis. The production of hemolytic factor by Candida species is affected by several factors such as glucose supplementation in the culture medium, blood source, presence of erythrocytes and hemoglobin, and presence of electrolytes. On the basis of existing achievements, more researches are still needed in order to extend our knowledge about the biochemical nature of hemolytic molecules produced by distinct Candida species, the mechanism of hemolysis, and the molecular basis of the hemolytic factor expression.

In vitro evaluation of hydrolytic enzyme activity and biofilm formation of Candida parapsilosis species complex from a nosocomial environment

INTRODUCTION:

Candida parapsilosis complex species, frequently found in hospital environments, have gained importance as etiological agents of candidemia.

METHODS:

Candida parapsilosis complex isolates from a nosocomial environment were identified and their hydrolitic enzyme activity and ability to form biofilm were characterized.

RESULTS:

Twenty-two C. parapsilosis sensu stricto isolates produced proteinase and three produced phospholipase. Most Candida metapsilosis isolates produced proteinase and one also produced phospholipase. All 29 isolates formed biofilms.

CONCLUSIONS:

The nosocomial environment may act as a reservoir for C. parapsilosis complex isolates with phenotypic features that could possibly lead to nosocomial infections and health complications in hospital patients.

Prevalence, virulence factors and antifungal susceptibility of Candida spp. isolated from bloodstream infections in a tertiary care hospital in Brazil

Candida spp. are responsible for 80% of all systemic fungal infections and are associated with high mortality rates. This study characterised 79 bloodstream isolates of C. albicans, C. glabrata, C. orthopsilosis, C. parapsilosis and C. tropicalis from patients in a Brazilian hospital. The susceptibility to amphotericin B, caspofungin, fluconazole and voriconazole was determined; virulence factor production was assessed based on haemolysin, phospholipase and proteinase activities, and the patients' clinical characteristics were analysed. C. albicans was the predominant species (44%), followed by C. glabrata (19%), C. tropicalis (19%), C. parapsilosis (14%) and C. orthopsilosis (4%). The candidemia incidence was 1.52 per 1000 admissions, and the crude mortality rate was 52%. One C. albicans isolate was resistant to fluconazole and voriconazole. Moreover, 20.2%, 2.5% and 3.8% of the isolates exhibited dose-dependent susceptibility to fluconazole, voriconazole and caspofungin, respectively. In conclusion, although the C. glabrata incidence was higher than that usually described in Brazil, its increase was previously observed in studies conducted worldwide. Furthermore, the azole resistance of the C. albicans isolate could be due to previous exposure to these antifungals. These results highlight the importance of epidemiological studies and will facilitate an improved understanding of candidemia in the studied hospital.

Virulence factors, antifungal susceptibility and molecular mechanisms of azole resistance among Candida parapsilosis complex isolates recovered from clinical specimens

Background

The aim of this study was to determine the biofilm formation, the extracellular enzymatic activities of 182 clinical isolates of the Candida parapsilosis complex.

Methods

Molecular identification of the C. parapsilosis species complex was performed using PCR RFLP of SADH gene and PCR sequencing of ITS region. The susceptibility of ours isolates to antifungal agents and molecular mechanisms underlying azole resistance were evaluated.

Results

63.5% of C. parapsilosis were phospholipase positive with moderate activity for the majority of strains. None of the C. metapsilosis or C. orthopsilosis isolates was able to produce phospholipase. Higher caseinase activities were detected in C. parapsilosis (Pz = 0.5 ± 0.18) and C. orthopsilosis (Pz = 0.49 ± 0.07) than in C. metapsilosis isolates (Pz = 0.72 ± 0.1). 96.5% of C. parapsilosis strains and all isolates of C. metapsilosis and C. orthopsilosis produced gelatinase. All the strains possessed the ability to show haemolysis on blood agar. C. metapsilosis exhibited the low haemolysin production with statistical significant differences compared to C. parapsilosis and C. orthopsilosis. The biofilm forming ability of C. parapsilosis was highly strain dependent with important heterogeneity, which was less evident with both C. orthopsilosis and C. metapsilosis.

Some C. parapsilosis isolates met the criterion for susceptible dose dependent to fluconazole (10.91%), itraconazole (16.36%) and voriconazole (7.27%). Moreover, 5.45% and 1.82% of C. parapsilosis isolates were respectively resistant to fluconazole and voriconazole. All strains of C. metapsilosis and C. orthopsilosis were susceptible to azoles; and isolates of all three species exhibited 100% of susceptibility to caspofungin, amphotericin B and 5-flucytosine.

Conclusions

A combination of molecular mechanisms, including the overexpression of ERG11, and genes encoding efflux pumps (CDR1, MDR1, and MRR1) were involved in azole resistance in C. parapsilosis.

Relationship between the Antifungal Susceptibility Profile and the Production of Virulence-Related Hydrolytic Enzymes in Brazilian Clinical Strains of Candida glabrata

Candida glabrata is a facultative intracellular opportunistic fungal pathogen in human infections. Several virulence-associated attributes are involved in its pathogenesis, host-pathogen interactions, modulation of host immune defenses, and regulation of antifungal drug resistance. This study evaluated the in vitro antifungal susceptibility profile to five antifungal agents, the production of seven hydrolytic enzymes related to virulence, and the relationship between these phenotypes in 91 clinical strains of C. glabrata. All C. glabrata strains were susceptible to flucytosine. However, some of these strains showed resistance to amphotericin B (9.9%), fluconazole (15.4%), itraconazole (5.5%), or micafungin (15.4%). Overall, C. glabrata strains were good producers of catalase, aspartic protease, esterase, phytase, and hemolysin. However, caseinase and phospholipase in vitro activities were not detected. Statistically significant correlations were identified between micafungin minimum inhibitory concentration (MIC) and esterase production, between fluconazole and micafungin MIC and hemolytic activity, and between amphotericin B MIC and phytase production. These results contribute to clarify some of the C. glabrata mechanisms of pathogenicity. Moreover, the association between some virulence attributes and the regulation of antifungal resistance encourage the development of new therapeutic strategies involving virulence mechanisms as potential targets for effective antifungal drug development for the treatment of C. glabrata infections.

Comparison of four molecular approaches to identify Candida parapsilosis complex species

Since the description of Candida orthopsilosis and C. metapsilosis in 2005, several methods have been proposed to identify and differentiate these species from C. parapsilosis sensu stricto. Species-specific uniplex polymerase chain reaction (PCR) was performed and compared with sequencing of the D1/D2 region of the LSU 28S rDNA gene, microsatellite typing of C. parapsilosis sensu stricto, and PCR-restriction fragment length polymorphism patterns in the ITS1-5.8S-ITS2 region of the rDNA gene. There was agreement between results of testing of 98 clinical isolates with the four PCR-based methods, with 59 isolates identified as C. parapsilosis sensu stricto, 37 as C. orthopsilosis, and two as C. metapsilosis.

1,10-Phenanthroline-5,6-Dione-Based Compounds Are Effective in Disturbing Crucial Physiological Events of Phialophora verrucosa

Phialophora verrucosa is a dematiaceous fungus able to cause chromoblastomycosis, phaeohyphomycosis and mycetoma. All these fungal diseases are extremely difficult to treat and often refractory to the current therapeutic approaches. Therefore, there is an urgent necessity to develop new antifungal agents to combat these mycoses. In this context, the aim of the present work was to investigate the effect of 1,10-phenanthroline-5,6-dione (phendione) and its metal-based derivatives [Ag(phendione)₂]ClO₄ = ([Ag(phendione)₂]⁺) and [Cu(phendione)₃](ClO₄)₂.4H₂O = ([Cu(phendione)₃]²⁺) on crucial physiological events of P. verrucosa conidial cells. Using the CLSI protocol, we have shown that phendione, [Ag(phendione)₂]⁺ and [Cu(phendione)₃]²⁺ were able to inhibit fungal proliferation, presenting MIC/IC₅₀ values of 12.0/7.0, 4.0/2.4, and 5.0/1.8 μM, respectively. [Cu(phendione)₃]²⁺ had fungicidal action and when combined with amphotericin B, both at sub-MIC (½ × MIC) concentrations, significantly reduced (~40%) the fungal growth. Cell morphology changes inflicted by phendione and its metal-based derivatives was corroborated by scanning electron microscopy, which revealed irreversible ultrastructural changes like surface invaginations, cell disruption and shrinkages. Furthermore, [Cu(phendione)₃]²⁺ and [Ag(phendione)₂]⁺ were able to inhibit metallopeptidase activity secreted by P. verrucosa conidia by approximately 85 and 40%, respectively. Ergosterol content was reduced (~50%) after the treatment of P. verrucosa conidial cells with both phendione and [Ag(phendione)₂]⁺. To different degrees, all of the test compounds were able to disturb the P. verrucosa conidia-into-mycelia transformation. Phendione and its Ag⁺ and Cu²⁺ complexes may represent a promising new group of antimicrobial agents effective at inhibiting P. verrucosa growth and morphogenesis.

First description of Candida nivariensis in Brazil: antifungal susceptibility profile and potential virulence attributes

This study evaluated the antifungal susceptibility profile and the production of potential virulence attributes in a clinical strain of Candida nivariensis for the first time in Brazil, as identified by sequencing the internal transcribed spacer (ITS)1-5.8S-ITS2 region and D1/D2 domains of the 28S of the rDNA. For comparative purposes, tests were also performed with reference strains. All strains presented low planktonic minimal inhibitory concentrations (PMICs) to amphotericin B (AMB), caspofungin (CAS), and voriconazole. However, our strain showed elevated planktonic MICs to posaconazole (POS) and itraconazole, in addition to fluconazole resistance. Adherence to inert surfaces was conducted onto glass and polystyrene. The biofilm formation and antifungal susceptibility on biofilm-growing cells were evaluated by crystal violet staining and a XTT reduction assay. All fungal strains were able to bind both tested surfaces and form biofilm, with a binding preference to polystyrene (p < 0.001). AMB promoted significant reductions (≈50%) in biofilm production by our C. nivariensis strain using both methodologies. This reduction was also observed for CAS and POS, but only in the XTT assay. All strains were excellent protease producers and moderate phytase producers, but lipases were not detected. This study reinforces the pathogenic potential of C. nivariensis and its possible resistance profile to the azolic drugs generally used for candidiasis management.

Assessment of biofilm formation by Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans

Reported herein is the ability of Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans conidia to adhere, differentiate into hyphae and form biofilms on both polystyrene and lung epithelial cells. To different degrees, all of the fungi adhered to polystyrene after 4 h, with a predominance of those with germinated conidia. Prolonged fungi-polystyrene contact resulted in the formation of a monolayer of intertwined mycelia, which was identified as a typical biofilm structure due to the presence of a viable mycelial biomass, extracellular matrix and enhanced antifungal resistance. Ultrastructural details were revealed by SEM and CLSM, showing the dense compaction of the mycelial biomass and the presence of channels within the organized biofilm. A similar biofilm structure was observed following the co-culture of each fungus with A549 cells, revealing a mycelial trap covering all of the lung epithelial monolayer. Collectively, these results highlight the potential for biofilm formation by these clinically relevant fungal pathogens.

The identification and differentiation of the Candida parapsilosis complex species by polymerase chain reaction-restriction fragment length polymorphism of the internal transcribed spacer region of the rDNA

Currently, it is accepted that there are three species that were formerly grouped under Candida parapsilosis: C. para- psilosis sensu stricto, Candida orthopsilosis, and Candida metapsilosis. In fact, the antifungal susceptibility profiles and distinct virulence attributes demonstrate the differences in these nosocomial pathogens. An accurate, fast, and economical identification of fungal species has been the main goal in mycology. In the present study, we searched sequences that were available in the GenBank database in order to identify the complete sequence for the internal transcribed spacer (ITS)1-5.8S-ITS2 region, which is comprised of the forward and reverse primers ITS1 and ITS4. Subsequently, an in silico polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to differentiate the C. parapsilosis complex species. Ninety-eight clinical isolates from patients with fungaemia were submitted for analysis, where 59 isolates were identified as C. parapsilosis sensu stricto, 37 were identified as C. orthopsilosis, and two were identified as C. metapsilosis. PCR-RFLP quickly and accurately identified C. parapsilosis complex species, making this method an alternative and routine identification system for use in clinical mycology laboratories.

Targeted gene disruption in Candida parapsilosis demonstrates a role for CPAR2_404800 in adhesion to a biotic surface and in a murine model of ascending urinary tract infection

Candida parapsilosis is an emerging opportunistic pathogen, second in frequency only to C. albicans and commonly associated with both mucosal and systemic infections. Adhesion to biotic surfaces is a key step for the development of mycoses. The C. parapsilosis genome encodes 5 predicted agglutinin-like sequence proteins and their precise role in the adhesion process still remains to be elucidated. In this study, we focused on the putative adhesin Cpar2_404800, in view of its high homology to the most important adhesion molecule in C. albicans. Two independent lineages of C. parapsilosis CPAR2_404800 heterozygous and null mutants were obtained by site-specific deletion. CPAR2_404800 mutants did not differ from wild-type strain in terms of in vitro growth or in their ability to undergo morphogenesis. However, when compared for adhesion to a biotic surface, CPAR2_404800 null mutants exhibited a marked reduction in their adhesion to buccal epithelial cells (>60% reduction of adhesion index). Reintroduction of one copy of CPAR2_404800 gene in the null background restored wild type phenotype. A murine model of urinary tract infection was used to elucidate the in vivo contribution of CPAR2_404800. A 0.5 and 1 log10 reduction in colony forming unit numbers (per gram) was observed respectively in bladder and kidneys obtained from mice infected with null mutant compared to wild-type infected ones. Taken together, these findings provide the first evidence for a direct role of CPAR2_404800 in C. parapsilosis adhesion to host surfaces and demonstrate its contribution to the pathogenesis of murine urinary candidiasis.

Candida parapsilosis (sensu lato) isolated from hospitals located in the Southeast of Brazil: Species distribution, antifungal susceptibility and virulence attributes

Candida parapsilosis (sensu lato), which represents a fungal complex composed of three genetically related species - Candida parapsilosis sensu stricto, Candida orthopsilosis and Candida metapsilosis, has emerged as an important yeast causing fungemia worldwide. The goal of the present work was to assess the prevalence, antifungal susceptibility and production of virulence traits in 53 clinical isolates previously identified as C. parapsilosis (sensu lato) obtained from hospitals located in the Southeast of Brazil. Species forming this fungal complex are physiologically/morphologically indistinguishable; however, polymerase chain reaction followed by restriction fragment length polymorphism of FKS1 gene has solved the identification inaccuracy, revealing that 43 (81.1%) isolates were identified as C. parapsilosis sensu stricto and 10 (18.9%) as C. orthopsilosis. No C. metapsilosis was found. The geographic distribution of these Candida species was uniform among the studied Brazilian States (São Paulo, Rio de Janeiro and Espírito Santo). All C. orthopsilosis and almost all C. parapsilosis sensu stricto (95.3%) isolates were susceptible to amphotericin B, fluconazole, itraconazole, voriconazole and caspofungin. Nevertheless, one C. parapsilosis sensu stricto isolate was resistant to fluconazole and another one was resistant to caspofungin. C. parapsilosis sensu stricto isolates exhibited higher MIC mean values to amphotericin B, fluconazole and caspofungin than those of C. orthopsilosis, while C. orthopsilosis isolates displayed higher MIC mean to itraconazole compared to C. parapsilosis sensu stricto. Identical MIC mean values to voriconazole were measured for these Candida species. All the isolates of both species were able to form biofilm on polystyrene surface. Impressively, biofilm-growing cells of C. parapsilosis sensu stricto and C. orthopsilosis exhibited a considerable resistance to all antifungal agents tested. Pseudohyphae were observed in 67.4% and 80% of C. parapsilosis sensu stricto and C. orthopsilosis isolates, respectively. The secretion of phytase (93% versus 100%), aspartic protease (88.4% versus 90%), esterase (20.9% versus 50%) and hemolytic factors (25.6% versus 40%) was detected in C. parapsilosis sensu stricto and C. orthopsilosis isolates, respectively; however, no phospholipase activity was identified. An interesting fact was observed concerning the caseinolytic activity, for which all the producers (53.5%) belonged to C. parapsilosis sensu stricto. Collectively, our results add new data on the epidemiology, antifungal susceptibility and production of potential virulence attributes in clinical isolates of C. parapsilosis complex.

Characterization of Virulence-Related Phenotypes in Candida Species of the CUG Clade

Candida species cause a variety of mucosal and invasive infections and are, collectively, the most important human fungal pathogens in the developed world. The majority of these infections result from a few related species within the "CUG clade," so named because they use a nonstandard translation for that codon. Some members of the CUG clade, such as Candida albicans, present significant clinical problems, whereas others, such as Candida (Meyerozyma) guilliermondii, are uncommon in patients. The differences in incidence rates are imperfectly correlated with virulence in animal models of infection, but comparative analyses that might provide an explanation for why some species are effective pathogens and others are not have been rare or incomplete. To better understand the phenotypic basis for these differences, we characterized eight CUG clade species--C. albicans, C. dubliniensis, C. tropicalis, C. parapsilosis, Clavispora lusitaniae, M. guilliermondii, Debaryomyces hansenii, and Lodderomyces elongisporus--for host-relevant phenotypes, including nutrient utilization, stress tolerance, morphogenesis, interactions with phagocytes, and biofilm formation. Two species deviated from expectations based on animal studies and human incidence. C. dubliniensis was quite robust, grouping in nearly all assays with the most virulent species, C. albicans and C. tropicalis, whereas C. parapsilosis was substantially less fit than might be expected from its clinical importance. These findings confirm the utility of in vitro measures of virulence and provide insight into the evolution of virulence in the CUG clade.

Phenotypic characteristics associated with virulence of clinical isolates from the Sporothrix complex

The Sporothrix complex members cause sporotrichosis, a subcutaneous mycosis with a wide spectrum of clinical manifestations. Several specific phenotypic characteristics are associated with virulence in many fungi, but studies in this field involving the Sporothrix complex species are scarce. Melanization, thermotolerance, and production of proteases, catalase, and urease were investigated in 61 S. brasiliensis, one S. globosa, and 10 S. schenckii strains. The S. brasiliensis strains showed a higher expression of melanin and urease compared with S. schenckii. These two species, however, presented similar thermotolerances. Our S. globosa strain had low expression of all studied virulence factors. The relationship between these phenotypes and clinical aspects of sporotrichosis was also evaluated. Strains isolated from patients with spontaneous regression of infection were heavily melanized and produced high urease levels. Melanin was also related to dissemination of internal organs and protease production was associated with HIV-coinfection. A murine sporotrichosis model showed that a S. brasiliensis strain with high expression of virulence factors was able to disseminate and yield a high fungal burden in comparison with a control S. schenckii strain. Our results show that virulence-related phenotypes are variably expressed within the Sporothrix complex species and might be involved in clinical aspects of sporotrichosis.

Biofilm formation by clinical isolates and its relevance to clinical infections

Reports of biofilms have increased exponentially in the scientific literature over the past two decades, yet the vast majority of these are basic science investigations with limited clinical relevance. Biofilm studies involving clinical isolates are most often surveys of isolate collections, but suffer from lack of standardization in methodologies for producing and assessing biofilms. In contrast, more informative clinical studies correlating biofilm formation to patient data have infrequently been reported. In this chapter, biofilm surveys of clinical isolates of aerobic and anaerobic bacteria, mycobacteria, and Candida are reviewed, as well as those pertaining to the unique situation of cystic fibrosis. In addition, the influence of host components on in vitro biofilm formation, as well as published studies documenting the clinical impact of biofilms in human infections, are presented.