Molecular identification, antifungal susceptibility profile, and biofilm formation of clinical and environmental Rhodotorula species isolates

Antifungal Tetrahydrocarbazole Compound CAR-8 Induces Endoplasmic Reticulum Stress in Candida albicans

The development of new effective antifungal agents is essential to combat fungal infections. Tetrahydrocarbazole has been exploited as a promising skeleton against various pathogenic microorganisms and is used to search for novel active antifungal compounds. In this study, a library composed of small tetrahydrocarbazole compounds was screened, and a potent antifungal agent, CAR-8, was identified with a minimum inhibitory concentration of 2-4 μg/mL against Candida albicans. CAR-8 showed strong fungicidal activities and killed almost all C. albicans within 3 h at a concentration of 16 μg/mL. At concentrations of 2 and 8 μg/mL, CAR-8 significantly inhibited the formation of hyphae and biofilms. Moreover, CAR-8 at 10 and 20 mg/kg reduced the fungal load and improved the survival in the C. albicans infection model in the invertebrate Galleria mellonella. Transcriptome analysis revealed significant changes in the expression of genes associated with protein processing in the endoplasmic reticulum (ER), ER-associated degradation, and unfolded protein response (UPR), which suggested that CAR-8 treatment induced ER stress. Moreover, CAR-8 treatment resulted in various phenotypes similar to tunicamycin, a classical ER stress inducer. These included nonconventional splicing of HAC1 mRNA, the fragmented morphology of ER, the distribution changes of GFP-Snc1 in Saccharomyces cerevisiae, and cell apoptosis probably caused by ER stress. More importantly, the disruption of IRE1 or HAC1 increased the sensitivity of C. albicans to CAR-8, confirming that the UPR signaling pathway was critical for CAR-8 resistance. Overall, our study identifies a potent ER stress-induced antifungal compound that will help the discovery of new antifungal drugs.

Emerging Fungal Pathogen Rhodotorula Species Isolated From a Patient With a Lung Malignancy

Rhodotorula is a genus of ubiquitous pigmented yeast found in the environment and as a commensal of human and animal microbiota. Previously considered nonpathogenic, Rhodotorula has emerged as an important cause of nosocomial and opportunistic infections in susceptible patients. While Rhodotorula spp. are common commensals in healthy individuals, the yeast may overgrow in patients with compromised immune systems causing disease. Herein, we provide a detailed presentation of a rare case involving a 79-year-old Caucasian female with a lung malignancy who developed massive cavitations in her lungs. The patient's lung tissue was cultured and grew an unidentified species of the genus Rhodotorula. The patient's health declined rapidly, and she expired due to hypoxemia. Clinicians must recognize patient groups potentially at risk for infection with Rhodotorula spp. Early identification and initiation of appropriate interventions are crucial in reducing mortality associated with this opportunistic fungal infection.

Study of Ecological Relationship of Yeast Species with Candida albicans in the Context of Vulvovaginal Infections

The role of the fungal community, the mycobiota, in the health of the vagina is currently an important area of research. The emergence of new sequencing technologies and advances in bioinformatics made possible the discovery of novel fungi inhabiting this niche. Candida spp. constitutes the most important group of opportunistic pathogenic fungi, being the most prevalent fungal species in vulvovaginal infections. However, fungi such as Rhodotorula spp., Naganishia spp. and Malassezia spp. have emerged as potential pathogens in this niche, and therefore it is clinically relevant to understand their ecological interaction with Candida spp. The main aim of this study was to evaluate the impact of yeasts on Candida albicans' pathogenicity, focusing on in-vitro growth, and biofilm formation at different times of co-culture and germ tube formation. The assays were performed with isolated species or with co-cultures of C. albicans (ATCC10231) with one other yeast species: Rhodotorula mucilaginosa (DSM13621), Malassezia furfur (DSM6170) or Naganishia albida (DSM70215). The results showed that M. furfur creates a symbiotic relationship with C. albicans, enhancing the growth rate of the co-culture (149.69%), and of germ tube formation of C. albicans (119.8%) and inducing a higher amount of biofilm biomass of the co-culture, both when mixed (154.1%) and preformed (166.8%). As for the yeasts R. mucilaginosa and N. albida, the relationship is antagonistic (with a significant decrease in all assays), thus possibly repressing the mixture's pathogenicity. These results shed light on the complex interactions between yeasts in the vaginal mycobiome.

Fungal Endocarditis: Pathophysiology, Epidemiology, Clinical Presentation, Diagnosis, and Management

Fungal endocarditis accounts for 1% to 3% of all infective endocarditis cases, is associated with high morbidity and mortality (>70%), and presents numerous challenges during clinical care. Candida spp. are the most common causes of fungal endocarditis, implicated in over 50% of cases, followed by Aspergillus and Histoplasma spp. Important risk factors for fungal endocarditis include prosthetic valves, prior heart surgery, and injection drug use. The signs and symptoms of fungal endocarditis are nonspecific, and a high degree of clinical suspicion coupled with the judicious use of diagnostic tests is required for diagnosis. In addition to microbiological diagnostics (e.g., blood culture for Candida spp. or galactomannan testing and PCR for Aspergillus spp.), echocardiography remains critical for evaluation of potential infective endocarditis, although radionuclide imaging modalities such as 18F-fluorodeoxyglucose positron emission tomography/computed tomography are increasingly being used. A multimodal treatment approach is necessary: surgery is usually required and should be accompanied by long-term systemic antifungal therapy, such as echinocandin therapy for Candida endocarditis or voriconazole therapy for Aspergillus endocarditis.

Removal of organic matter and nitrogen from dairy effluents in a structured bed reactor operated with intermittent aeration

The objective of this research was to evaluate the performance of a structured bed reactor (SBRIA), carried out with intermittent aeration (IA), in the removal of organic matter and nitrogen from dairy effluent, when run with different organic loading rates (OLR). The SBRIA was operated for 227 days, with 2:1 AI cycles (2 h with aeration on and 1 h off) and Hydraulic Retention Time (HRT) of 16 h. Three phases, with different OLR, were evaluated: phases A (1000 gCOD m-3 day-1 - 63 days), B (1400 gCOD m-3 day-1 - 94 days), and C (1800 gCOD m-3 day-1 - 70 days). The percentage of COD, NH4+-N removal, and nitrogen removal, respectively, were above 85 ± 7%, 73 ± 27%, and 83 ± 5, in all phases. There was no accumulation of the oxidized forms of nitrogen in the reactor. The kinetic test, performed to evaluate the nitrification and denitrification in the system, indicated that even in dissolved oxygen concentrations of 4.5 mg L-1, it was possible to obtain the denitrification process in the system. The results demonstrate that the reactor under study has positive characteristics to be used as an alternative for removing the removal of organic material and nitrogen in the biological treatment of dairy effluents.

Shotgun proteomics for the identification of yeasts responsible for pink/red discoloration in commercial dairy products

Pink/red discoloration encompasses a series of relatively common spoilage defects of commercial dairy products. In this study, we used shotgun proteomics to identify the microorganism responsible for the production of intensely red-coloured slimes found on the surface of freshly opened commercial spreadable cheese and yogurt samples. Proteome-wide characterization of microbial proteins allowed to identify 1042 and 687 gene products from Rhodotorula spp. in spreadable cheese and yogurt samples, respectively, while no significant protein scores from other microorganisms were recorded. Subsequent microbiological analyses and sequencing of the 26S rRNA gene region supported the proteomic results demonstrating that the microorganism involved was Rhodotorula mucilaginosa, a carotenoid - producing basidiomycetous that can be potentially pathogenic to humans, especially for immunocompromised individuals. This is the first time that shotgun proteomics has been used to identify a microorganism responsible for spoilage in dairy products, proposing it as a relatively fast, sensitive, and reliable alternative or complement to conventional methods for microbial identification.

Rhodotorula sp. as a cell factory for production of valuable biomolecules

Rhodotorula sp. are well-known for their ability to biosynthesize a diverse range of valuable biomolecules, including carotenoids, lipids, enzymes, and polysaccharides. Despite the high number of studies conducted using Rhodotorula sp. at the laboratory scale, most of these do not address all processual aspects necessary for scaling up these processes for industrial applications. This chapter explores the potential of Rhodotorula sp. as a cell factory for the production of distinct biomolecules, with a particular emphasis on exploring their use from a biorefinery perspective. Through in-depth discussions of the latest research and insights into non-conventional applications, we aim to provide a comprehensive understanding of Rhodotorula sp.'s ability to produce biofuels, bioplastics, pharmaceuticals, and other valuable biochemicals. This book chapter also examines the fundamentals and challenges associated with the optimizing upstream and downstream processing of Rhodotorula sp-based processes. We believe that through this chapter, readers with different levels of expertise will gain insights into strategies for enhancing the sustainability, efficiency, and effectiveness of producing biomolecules using Rhodotorula sp.

Biotechnological applications of biofilms formed by osmotolerant and halotolerant yeasts

Many microorganisms are capable of developing biofilms under adverse conditions usually related to nutrient limitation. They are complex structures in which cells (in many cases of different species) are embedded in the material that they secrete, the extracellular matrix (ECM), which is composed of proteins, carbohydrates, lipids, and nucleic acids. The ECM has several functions including adhesion, cellular communication, nutrient distribution, and increased community resistance, this being the main drawback when these microorganisms are pathogenic. However, these structures have also proven useful in many biotechnological applications. Until now, the most interest shown in these regards has focused on bacterial biofilms, and the literature describing yeast biofilms is scarce, except for pathological strains. Oceans and other saline reservoirs are full of microorganisms adapted to extreme conditions, and the discovery and knowledge of their properties can be very interesting to explore new uses. Halotolerant and osmotolerant biofilm-forming yeasts have been employed for many years in the food and wine industry, with very few applications in other areas. The experience gained in bioremediation, food production and biocatalysis with bacterial biofilms can be inspiring to find new uses for halotolerant yeast biofilms. In this review, we focus on the biofilms formed by halotolerant and osmotolerant yeasts such as those belonging to Candida, Saccharomyces flor yeasts, Schwannyomyces or Debaryomyces, and their actual or potential biotechnological applications. KEY POINTS: • Biofilm formation by halotolerant and osmotolerant yeasts is reviewed. • Yeasts biofilms have been widely used in food and wine production. • The use of bacterial biofilms in bioremediation can be expanded to halotolerant yeast counterparts.

Current research on fungi in chronic wounds

The occurrence of chronic wounds is a major global health issue. These wounds are difficult to heal as a result of disordered healing mechanisms. The most common types of chronic wounds are diabetic ulcers, pressure ulcers, arterial/venous ulcers and nonhealing surgical wounds. Although bacteria are an important cause of chronic nonhealing wounds, fungi also play a substantial role in them. The fungal infection rate varies with different chronic wound types, but overall, the prevalence of fungi is extremely underestimated in the clinical treatment and management of chronic wounds. Wounds and ulcers can be colonized by host cutaneous, commensal or environmental fungi and evolve into local infections, causing fungemia as well as invasive fungal disease. Furthermore, the fungi involved in nonhealing wound-related infections help commensal bacteria resist antibiotics and the host immune response, forcing wounds to become reservoirs for multiresistant species, which are considered a potential key factor in the microbial bioburden of wounds and ulcers. Fungi can be recalcitrant to the healing process. Biofilm establishment is the predominant mechanism of fungal resistance or tolerance to antimicrobials in chronic nonhealing wounds. Candida albicans yeast and Trichophyton rubrum filamentous fungi are the main fungi involved in chronic wound infection. Fungal species diversity and drug resistance phenotypes in different chronic nonhealing wound types will be emphasized. In this review, we outline the latest research on fungi in chronic wounds and discuss challenges and future perspectives related to diagnosing and managing chronic wounds.

Persistence of an epidemic cluster of Rhodotorula mucilaginosa in multiple geographic regions in China and the emergence of a 5-flucytosine resistant clone

Rhodotorula mucilaginosa, an environmental yeast widely used in industry and agriculture, is also an opportunistic pathogen resistant to multi-antifungals. During the national surveillance in China, R. mucilaginosa has been documented from various hospitals and regions. At present, the molecular epidemiology of invasive infections caused by R. mucilaginosa and their resistance profiles to antifungals were unknown. Here we collected 49 strains from four hospitals located in different geographic regions from 2009 to 2019 in China, determined their genotypes using different molecular markers and quantified susceptibilities to various antifungals. Sequencing of ITS and D1/D2 regions in rDNA indicated that 73.5% (36/49) of clinical strains belong to same sequence type (rDNA type 2). Microsatellite (MT) genotyping with 15 (recently developed) tandem repeat loci identified 5 epidemic MT types, which accounted for 44.9% (22/49) of clinical strains, as well as 27 sporadic MT types. Microsatellite data indicated that the presence of an epidemic cluster including 35 strains (71.4%) repeatedly isolated in four hospitals for eight years. Single nucleotide variants (SNVs) from the whole genome sequence data also supported the clustering of these epidemic strains due to low pairwise distance. In addition, phylogenetic analysis of SNVs from these clinical strains, together with environmental and animal strains showed that the closely related epidemic cluster strains may be opportunistic, zoonotic pathogens. Also, molecular data indicated a possible clonal transmission of pan echinocandins-azoles-5-flucytosine resistant R. mucilaginosa strains in hospital H01. Our study demonstrated that R. mucilaginosa is a multi-drug resistant pathogen with the ability to cause nosocomial infection.

Clinical Challenges of Emerging and Re-Emerging Yeast Infections in the Context of the COVID-19 Pandemic

During the geological eras, some fungi, through adaptation and/or environmental/ecological pressure, interacted directly and indirectly with humans, through occasionally harmful interaction interdependent on the individual’s immunological condition. Infections caused by yeasts are underreported, subjugated, and underdiagnosed, and treatment is restricted to a few drugs, even after the significant progress of medicine and pharmacology. In the last centuries, antagonistically, there has been an exponential increase of immunocompromised individuals due to the use of immunosuppressive drugs such as corticosteroids, increased cases of transplants, chemotherapeutics, autoimmune diseases, neoplasms, and, more recently, coronavirus disease 2019 (COVID-19). This review aims to survey emerging and re-emerging yeast infections in the current clinical context. Currently, there is an immense clinical challenge for the rapid and correct diagnosis and treatment of systemic mycoses caused by yeasts due to the terrible increase in cases in the current context of COVID-19.

New Perspectives on Antimicrobial Agents: Isavuconazole

Isavuconazole is the newest of the clinically available advanced generation triazole antifungals and is active against a variety of yeasts, molds, and dimorphic fungi. Its current FDA-approved indications include the management of invasive aspergillosis as well as mucormycosis, though the latter indication is supported by limited clinical data. Isavuconazole did not achieve noninferiority to caspofungin for the treatment of invasive candidiasis and therefore lacks an FDA-approved indication for this invasive disease. Significant advantages of isavuconazole, primarily over voriconazole but in some circumstances posaconazole as well, make it an appealing option for the management of complex patients with invasive fungal infections. These potential advantages include lack of QTc interval prolongation, more predictable pharmacokinetics, a less complicated drug interaction profile, and improved tolerability, particularly when compared to voriconazole. This review discusses these topics in addition to addressing the in vitro activity of the compound against a variety of fungi and provides insight into other distinguishing factors among isavuconazole, voriconazole, and posaconazole. The review concludes with an opinion section in which the authors provide the reader with a framework for the current role of isavuconazole in the antifungal armamentarium and where further data are required.

Rhodotorula mucilaginosa Fungemia, a Rare Opportunistic Infection without Central Venous Catheter Implantation, Successfully Treated by Liposomal Amphotericin B

Background. Fungemia due to Rhodotorula mucilaginosa is rare and highly resistance to antifungal therapy. Since most cases of R. mucilaginosa fungemia are attributed to medical devices, limited information is currently available on infection without central venous catheter (CVC) implantation. We herein report a case of R. mucilaginosa fungemia without implantation of CVC, successfully treated by liposomal amphotericin B (L-AMB). Case Presentation. An 81-year-old man with a history of chronic obstructive lung disease and rheumatoid arthritis was admitted with dyspnea and fever. The present case had no previous history of CVC implantation. Candidemia was suspected based on yeast and salmon-pink colonies in blood cultures, and thus, micafungin (MCFG) was administered. The isolated yeast was identified as R. mucilaginosa, which exhibited resistance to MCFG. Therefore, antifungal therapy was changed to L-AMB. The sterile blood culture and defervescence were observed from the initiation of L-AMB. Conclusion. Although the obvious entry point was unclear, long-term immunosuppressive therapy for RA may have damaged the gastrointestinal tract, which leading to the bacterial translocation of R. mucilaginosa. An early class switch to L-AMB was effective. Physicians need to consider the administration of L-AMB in cases suspected of R. mucilaginosa fungemia following the detection of salmon-pink colonies in blood cultures.

Determinants and Interactions of Oral Bacterial and Fungal Microbiota in Healthy Chinese Adults

Numerous studies have examined the composition of and factors shaping the oral bacterial microbiota in healthy adults; however, similar studies on the less dominant yet ecologically and clinically important fungal microbiota are scarce. In this study, we characterized simultaneously the oral bacterial and fungal microbiomes in a large cohort of systemically healthy Chinese adults by sequencing the bacterial 16S rRNA gene and fungal internal transcribed spacer. We showed that different factors shaped the oral bacterial and fungal microbiomes in healthy adults. Sex and age were associated with the alpha diversity of the healthy oral bacterial microbiome but not that of the fungal microbiome. Age was also a major factor affecting the beta diversity of the oral bacterial microbiome; however, it only exerted a small effect on the oral fungal microbiome when compared with other variables. After controlling for age and sex, the bacterial microbiota structure was most affected by marital status, recent oral conditions and oral hygiene-related factors, whereas the fungal microbiota structure was most affected by education level, fruits and vegetables, and bleeding gums. Bacterial-fungal interactions were limited in the healthy oral microbiota, with the strongest association existing between Pseudomonas sp. and Rhodotorula dairenensis. Several bacterial amplicon sequence variants (ASVs) belonging to Veillonella atypica and the genera Leptotrichia, Streptococcus and Prevotella_7 and fungal ASVs belonging to Candida albicans and the genus Blumeria were revealed as putative pivotal members of the healthy oral microbiota. Overall, our study has facilitated understanding of the determining factors and cross-kingdom interactions of the healthy human oral microbiome. IMPORTANCE Numerous studies have examined the bacterial community residing in our oral cavity; however, information on the less dominant yet ecologically and clinically important fungal members is limited. In this study, we characterized simultaneously the oral bacterial and fungal microbial communities in a large cohort of healthy Chinese adults, examined their associations with an array of host factors, and explored potential interactions between the two microbial groups. We showed that different factors shape the diversity and structure of the oral bacterial and fungal microbial communities in healthy adults, with, for instance, sex and age only associated with the diversity of the bacterial community but not that of the fungal community. Besides, we found that bacterial-fungal interactions are limited in the healthy oral cavity. Overall, our study has facilitated understanding of the determining factors and bacterial-fungal interactions of the healthy human oral microbial community.

All You Need To Know and More about the Diagnosis and Management of Rare Yeast Infections

Invasive infections with emerging yeasts such as Geotrichum, Saprochaete/Magnusiomyces, Trichosporon, and other species are associated with high morbidity and mortality rates. Due to the rarity and heterogeneity of these yeasts, medical mycology has lacked guidance in critical areas affecting patient management. Now, physicians and life scientists from multiple disciplines and all world regions have united their expertise to create the "Global guideline for the diagnosis and management of rare yeast infections: an initiative of the European Confederation of Medical Mycology in cooperation with the International Society for Human and Animal Mycology and the American Society for Microbiology." Recommendations are stratified for high- and low-resource settings and are therefore applicable worldwide. The advantages and disadvantages of various diagnostic methods and treatment options are outlined. This guideline reflects the current best-practice management for invasive rare yeast infections in a range of settings, with the intent of establishing a global standard of care for laboratorians and clinicians alike.

Vulvovaginal candidiasis and current perspectives: new risk factors and laboratory diagnosis by using MALDI TOF for identifying species in primary infection and recurrence

Vulvovaginal candidiasis (VVC), considered the second cause of genital infection among women, has pathogenic mechanisms still to be elucidated and unknown risk factors. Prevalence studies with laboratory diagnosis (at first diagnosis and recurrence) are uncommon, especially using MALDI TOF, used in this clinical, epidemiological, and laboratory study for evaluating candidiasis, and identifying unknown risk factors. To obtain clinical and epidemiological data, patients were questioned, and there was material collection. Samples collected were identified by using phenotypic and presumptive methods and confirmed by MALDI TOF. This study analyzed 278 patients, divided into symptomatic (n = 173) and asymptomatic (n = 105) groups. Regarding the main candidiasis symptoms (discharge, itching, and burning), only 50.3% of patients described these concomitant symptoms, showing a positive predictive value of 67.8%. Regarding the risk factors investigated, there was a statistical correlation between candidiasis and dairy products, gut transit, contraceptive use, respiratory allergy, and panty liners, describing new risk factors related to intestinal and vaginal dysbiosis. After Candida species analysis and confirmation, the primary prevalence was 80.9% (Candida albicans), 15.2% (non-albicans), 1% (Rhodotorula mucilaginosa), and 1.9% (unidentified species). In recurrence, the prevalence was 66.7% (C. albicans) and 33.3% (non-albicans). The presence of symptoms has low positive predictive value for the diagnosis of candidiasis, even when considering the classic triad of symptoms. Laboratory identification of yeast species is essential for correct treatment, preventing the resistance to antifungals and the high recurrence. In addition, dairy products and bowel habits, both related to intestinal and vaginal dysbiosis, may be associated with VVC.

Species identification, antifungal susceptibility profiles and biofilm formation attributes of Rhodotorula isolates from ocular infections

BACKGROUND

Members of genus Rhodotorula are widely distributed in nature and have been traditionally considered non-pathogenic. Last few decades have seen the yeast as an emerging pathogen. We observed increase in numbers of Rhodotorula isolates from ocular infections in last few years, thus this prospective study was planned.

OBJECTIVES

To identify the species of Rhodotorula isolates from ocular infections. To know the antifungal susceptibilities and study the biofilm formation attributes of the isolates.

MATERIALS AND METHODS

Rhodotorula isolates were speciated using conventional methods, Matrix Assisted Laser Desorption and Ionisation - Time of Flight (MALDI- TOF) and sequencing of ITS region of ribosomal DNA. Antifungal susceptibility testing (AFST) was done using disc diffusion and E-test. Biofilm formation was studied using XTT [2,3-bis (2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetra-zolium-5-carboxanilide] assay.

RESULTS

Twenty four isolates (92.3%) were identified as R. mucilaginosa and two as R. Minuta. AFST showed high MICs against Fluconazole, Amphotericin-B, Caspofungin, Micafungin and Flucytosine; MIC distribution from low to very high against Voriconazole, Itraconazole and Natamycin; and very low MICs against Posaconazole 57.7% of isolates were strong biofilm producers, 23.1% were moderate, and 19.2% were non producers.

CONCLUSIONS

This is the first prospective study on species distribution, antifungal susceptibility and biofilm production attributes of Rhodotorula isolates from ocular infections; also first time demonstrating the utility of proteomics based MALDI-TOF in diagnosing Rhodotorula up to species level. The study has shown high MICs against the conventional azoles, Amphotericin-B and Flucytosine. However, low MICs against Posaconazole and Natamycin give a hope for their possible therapeutic use.

Raw bovine milk as a reservoir of yeast with virulence factors and decreased susceptibility to antifungal agents

In recent years, increased rates of yeast infections in humans and animals have been recognized worldwide. Since animals may represent a source of yeast infections for humans, knowing the antifungal susceptibility profile of yeast isolates from milk and evaluating their pathogenic potential would be of great medical importance. Therefore, the aim of this survey was to study yeast diversity in milk samples, analyze the hemolytic and phospholipase activities of isolates and determine minimal inhibition concentration (MIC) for fluconazole, voriconazole and flucytosine. Out of 66 yeast isolates obtained from 910 individual raw milk samples from subclinically infected cows, 26 different yeast species were determined based on sequencing of the D1/D2 and ITS regions. Among them, Pichia kudriavzevii (formerly known as Candida krusei), Kluyveromyces marxianus (formerly known as Candida kefyr) and Debaryomyces hansenii (formerly known as Candida famata) were the most commonly identified. Hemolysin and/or phospholipase activity was observed in 66.7% of isolates. The elevated MIC for fluconazole was determined in 16 isolates from 11 species. The findings of this study demonstrate that yeast isolates from raw milk have the potential to express virulence attributes such as hemolysin and phospholipase, and additionally, some of these strains showed elevated MIC to fluconazole or to flucytosine.

LAY ABSTRACT

We identified 66 yeast isolates, including 26 different yeast species from 910 individual milk samples. Our results indicate that individual milk samples may serve as a source of yeasts with the potential to trigger infection and may have reduced sensitivity to tested antifungal agents.

Candidemia among Iranian Patients with Severe COVID-19 Admitted to ICUs

As a novel risk factor, COVID-19 has led to an increase in the incidence of candidemia and an elevated mortality rate. Despite being of clinical importance, there is a lack of data regarding COVID-19-associated candidemia (CAC) among Iranian patients. Therefore, in this retrospective study, we assessed CAC epidemiology in the intensive care units (ICUs) of two COVID-19 centers in Mashhad, Iran, from early November 2020 to late January 2021. Yeast isolates from patients’ blood were identified by 21-plex polymerase chain reaction (PCR) and sequencing, then subjected to antifungal susceptibility testing according to the CLSI M27-A3 protocol. Among 1988 patients with COVID-19 admitted to ICUs, seven had fungemia (7/1988; 0.03%), among whom six had CAC. The mortality of the limited CAC cases was high and greatly exceeded that of patients with COVID-19 but without candidemia (100% (6/6) vs. 22.7% (452/1988)). In total, nine yeast isolates were collected from patients with fungemia: five Candida albicans, three C. glabrata, and one Rhodotorula mucilaginosa. Half of the patients infected with C. albicans (2/4) were refractory to both azoles and echinocandins. The high mortality of patients with CAC, despite antifungal therapy, reflects the severity of the disease in these patients and underscores the importance of rapid diagnosis and timely initiation of antifungal treatment.

Low sensitivity of conventional fungal agars in fungemia by Rhodotorula mucilaginosa: description of two cases

Background

Although most bloodstream yeast infections are caused by Candida spp., infections by rare or less common species have increased in recent years. Diagnosis of infections caused by these species is difficult due to the lack of specific symptoms and adequate diagnostic tools.

Cases presentation

We describe two cases of fungemia by Rhodotorula mucilaginosa within a few months of each other, in a secondary Spanish hospital. In both cases, diagnosis was challenging. Blood subcultures in conventional fungal media were persistently negatives and the use of non-conventional fungal media was essential for isolating the yeasts and achieving a correct diagnosis. 1–3 beta-d-glucan detection and a panfungal PCR assay were helpful techniques to confirm the diagnosis

Conclusion

It is highly important to establish an early diagnosis for fungemia. The process is challenging because often non-specific symptoms are presents. When yeasts grow in blood cultures other genera than Candida spp. could be the cause of infection. Patient risk factors should be assessed to incorporate alternative culture media and the available rapid diagnostic test, in order to provide an early recognition of the pathogen.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-021-00427-w.

New Approach to Antifungal Activity of Fluconazole Incorporated into the Porous 6-Anhydro-α-l-Galacto-β-d-Galactan Structures Modified with Nanohydroxyapatite for Chronic-Wound Treatments-In Vitro Evaluation

New fluconazole-loaded, 6-Anhydro-α-l-Galacto-β-d-Galactan hydrogels incorporated with nanohydroxyapatite were prepared and their physicochemical features (XRD, X-ray Diffraction; SEM-EDS, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy; ATR-FTIR, Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy), fluconazole release profiles and enzymatic degradation were determined. Antifungal activity of pure fluconazole was tested using Candida species (C. albicans, C. tropicalis, C. glabarata), Cryptococcus species (C. neoformans, C. gatti) and Rhodotorula species (R. mucilaginosa, R. rubra) reference strains and clinical isolates. Standard microdilution method was applied, and fluconazole concentrations of 2-250 µg/mL were tested. Moreover, biofilm production ability of tested isolates was tested on the polystyrene surface at 28 and 37 ± 0.5 °C and measured after crystal violet staining. Strains with the highest biofilm production ability were chosen for further analysis. Confocal microscopy photographs were taken after live/dead staining of fungal suspensions incubated with tested hydrogels (with and without fluconazole). Performed analyses confirmed that polymeric hydrogels are excellent drug carriers and, when fluconazole-loaded, they may be applied as the prevention of chronic wounds fungal infection.

Evaluation of Rhodotorula spp. contamination in hospital environments

Microbiological monitoring of air and surfaces is a valuable tool for assessing the level of environmental contamination by bacteria and fungi in hospitals, especially in high-risk wards. The presence of these microorganisms requires strict control in view of their role as opportunistic pathogens. As regard yeasts, Candida albicans is one of the main opportunistic pathogens. However, in recent years, many other "non-Albicans" species have been identified that are implicated in the onset of both localised infections in immunocompetent patients and systemic infections in immunocompromised patients. The aim of the work was to evaluate the frequency of isolation of Rhodotorula spp. in environmental samples of hospital origin in order to highlight how its presence may represent an increased risk for hospitalised patients. The samples were taken in at-risk wards, divided into six types of environments, in three hospitals in southern Sardinia between 2016 and 2019. The presence of moulds and yeasts was higher in the air (55.7%) than on surfaces (44.3%) in the hospital environments (p < 0.001). Similarly, the isolation frequency of Rhodotorula spp. was found to be greater (p < 0.001) in the air (14.2%) than on surfaces (9.2%). This study made it possible to evaluate the presence of pathogenic fungi in hospital environments, paying particular attention to Rhodotorula spp. since it is an emerging opportunistic yeast. It also highlights the importance of control measures especially in those where immunocompromised patients are present.

Distinct fungal plastisphere across different river functional zones: A watershed scale study

Fungi not only play important roles in biogeochemical processes but also can form biofilm on plastic debris. However, knowledge of structure composition and spatiotemporal pattern of fungal plastisphere on different kinds of plastic debris in river with specific usages, known as river functional zones, is still missing. In this study, we investigated the spatial distribution of the fungal plastisphere across a complete urban river with different functional zones (drinking, farm irrigation, aquaculture, and tail lake). Our research was performed based on both field residual plastic debris collection and a 30-day field in situ incubation experiments. Our study revealed that plastic debris enriched distinct fungal communities (including pathogenic fungi) significantly different from the surrounding water. Tracking the source of the fungi colonized on plastic debris suggested that the fungal taxa colonized on the different kinds of plastic debris were not from the surrounding water. Human activities had considerable effects on the fungal community structure on plastic debris, and the plastisphere fungal community structure strikingly varied across different river functional zones. Plastisphere may be used as an indicator for fungi biogeography and pathogenic fungi pollution in river with different functional zones. These findings are essential for ecological risk assessment and management decisions for pollution control of plastic debris and maintaining ecological health.

Molecular identification, biofilm formation and antifungal susceptibility of Rhodotorula spp

Luliconazole is an imidazole antifungal agent used in topical form for the treatment of onychomycosis and dermatophytosis. In vitro activity of luliconazole against dermatophytes, Candida, black fungi, Fusarium and Aspergillus species have been investigated. Rhodotorula spp. are environmental yeasts and emerged as opportunistic pathogens among immunocompromised patients. Rhodotorula's human infections are usually resistant to treatment with antifungal drugs especially triazoles and echinocandins. The present study aimed at the molecular detection of environmental isolates of Rhodotorula spp. Then, antifungal efficacy of luliconazole was evaluated against isolates and compared to other routine systemic antifungals including; caspofungin, posaconazole, fluconazole, itraconazole, amphotericin B, and voriconazole. The biofilm production of Rhodotorula isolates was also evaluated. In this study, 39 isolates of Rhodotorula spp. were isolated from the environment, detected using molecular methods, and tested against luliconazole. Then, the anti-fungal activity of luliconazole compared with several routine antifungals. Also, biofilm formation by using a crystal violet staining assay was performed. Our finding showed that luliconazole has a very high minimum inhibitory concentration (MIC) value (1-8 µg/ml) against Rhodotorula spp. Besides, 100% of Rhodotorula strains were resistant to caspofungin, followed by fluconazole 94.7% and voriconazole 74.4%. Amphotericin B was demonstrated excellent in vitro activity against this genus. Our result indicated that 59% of Rhodotorula spp. were in the mid-range of biofilm production. Our results indicated that luliconazole does not effective against the genus Rhodotorula. Furthermore, amphotericin B is the best drug against this genus in comparison to caspofungin and other azole drugs.

Rhodotorula dairenensis fungemia in a patient with cancer

BACKGROUND

Rhodotorula species were traditionally considered non-virulent environmental microorganisms, but are nowadays considered important human pathogens, especially in immunocompromised individuals.

CASE REPORT

We present the case of a 73 year-old man with diarrhea, anorexia and fever. In the blood analyses, both aerobic blood culture bottles yielded the growth of Rhodotorula dairenensis. The MALDI-TOF MS score was inadequate to provide an identification, which was achieved by means of molecular techniques. Treatment with an echinocandin was started, but the patient died.

CONCLUSIONS

Basidiomycetous yeast genera such as Rhodotorula can cause invasive and severe infections, e.g., fungemia, especially in patients with central venous catheter or another indwelling device.

Microbiological and virulence aspects of Rhodotorula mucilaginosa

We aimed to characterize microbiologically clinical isolates of R. mucilaginosa isolated from colonization of a patient with chronic renal disease (CKD), as well as to evaluate their phylogeny, antifungal susceptibility, virulence, and pathogenicity in order to infer the potential to become a possible infective agent. For this study, two isolates of R. mucilaginosa from oral colonization of a CKD patient were isolated, identified and characterized by classical (genotypic and phenotypic) methods. Susceptibility to conventional antifungals was evaluated, followed by biofilm production, measured by different techniques (total biomass, metabolic activity, colony forming units and extracellular matrix quantification). Finally, the pathogenicity of yeast was evaluated by infection of Tenebrio molitor larvae. All isolates were resistant to azole and sensitive to polyenes and they were able to adhere and form biofilm on the abiotic surface of polystyrene. In general, similar profiles among isolates were observed over the observed periods (2, 24, 48 and 72 hours). Regarding extracellular matrix components of biofilms at different maturation ages, R. mucilaginosa was able to produce eDNA, eRNA, proteins, and polysaccharides that varied according to time and the strain. The death curve in vivo model showed a large reduction in the survival percentage of the larvae was observed in the first 24 hours, with only 40 % survival at the end of the evaluation. We infer that colonization of chronic renal patients by R. mucilaginosa offers a high risk of serious infection. And also emphasize that the correct identification of yeast is the main means for an efficient treatment.

Colonization of Wild Saccharomyces cerevisiae Strains in a New Winery

The aim of this work was to study the fungal colonization of a new winery over time, specifically for Saccharomyces cerevisiae. Therefore, we analyzed the flora present before the arrival of the first harvest on the floor, the walls and the equipment of this new winery by Illumina MiSeq. The genus Saccharomyces (≤0.3%) was detected on floor and equipment but the presence of S. cerevisiae species was not reported. Wild S. cerevisiae strains were isolated from a ‘Pied de Cuve’ used during the first vintage to ensure the alcoholic fermentation (AF). Among 25 isolates belonging to this species, 17 different strains were identified highlighting a great intraspecific diversity. S. cerevisiae strains were also isolated from different vats throughout the spontaneous fermentations during the first vintage. The following year, some of these strains were isolated again during AF. Some of them (four) were found in the winery equipment before the arrival of the third harvest suggesting a potential colonization by these strains. To better understand what promotes the yeast colonization of the winery’s environment, the ability to form a biofilm on solid surfaces for eight colonizing or non-colonizing strains was studied. This capacity, different according to the strains, could partly explain the colonization observed for certain strains.

MIC distributions for amphotericin B, fluconazole, itraconazole, voriconazole, flucytosine and anidulafungin and 35 uncommon pathogenic yeast species from the UK determined using the CLSI broth microdilution method

Background

Epidemiological cut-off values and clinical interpretive breakpoints have been developed for a number of antifungal agents with the most common Candida species that account for the majority of infections due to pathogenic yeasts species. However, less-common species, for which susceptibility data are limited, are increasingly reported in high-risk patients and breakthrough infections.

Methods

The UK National Mycology Reference Laboratory performs routine antifungal susceptibility testing of clinical yeast isolates submitted from across the UK. Between 2002 and 2016, &gt;32 000 isolates representing 94 different yeast species were referred to the laboratory. Here we present antifungal susceptibility profiles generated over this period for amphotericin B, fluconazole, voriconazole, itraconazole, anidulafungin and flucytosine against 35 species of uncommon yeast using CLSI methodologies. MIC data were interpreted against epidemiological cut-off values and clinical breakpoints developed with Candida albicans, in order to identify species with unusually skewed MIC distributions that potentially indicate resistance.

Results

Potential resistance to at least one antifungal agent (&gt;10% of isolates with MICs greater than the epidemiological cut-off or clinical breakpoint) was evidenced for 29/35 species examined here. Four species exhibited elevated MICs with all of the triazole antifungal drugs against which they were tested, and 21 species exhibited antifungal resistance to agents from at least two different classes of antifungal agent.

Conclusions

This study highlights a number of yeast species with unusual MIC distributions and provides data to aid clinicians in deciding which antifungal regimens may be appropriate when confronted with infections with rarer yeasts.

New advances on the Brettanomyces bruxellensis biofilm mode of life

The wine spoilage yeast Brettanomyces bruxellensis can be found at several steps in the winemaking process due to its resistance to multiple stress conditions. The ability to form biofilm is a potential resistance strategy, although it has been given little attention so far for this yeast. In this work, the capacity to form biofilm and its structure were explored in YPD medium and in wine. Using microsatellite analysis, 65 isolates were discriminated into 5 different genetic groups from which 12 strains were selected. All 12 strains were able to form biofilm in YPD medium on a polystyrene surface. The presence of microcolonies, filamentous cells and extracellular polymeric substances, constituting the structure of the biofilm despite a small thickness, were highlighted using confocal and electronic microscopy. Moreover, different cell morphologies according to genetic groups were highlighted. The capacity to form biofilm in wine was also revealed for two selected strains. The impact of wine on biofilms was demonstrated with firstly considerable biofilm cell release and secondly growth of these released biofilm cells, both in a strain dependent manner. Finally, B. bruxellensis has been newly described as a producer of chlamydospore-like structures in wine, for both planktonic and biofilm lifestyles.

Molecular identification and antifungal susceptibility testing of Pucciniomycotina red yeast clinical isolates from Rio de Janeiro, Brazil

Infections caused by Rhodotorula spp. are increasing worldwide. This study identified, through the light of the new taxonomic advances on the subphylum Pucciniomycotina, 16 isolates from blood cultures and compared their antifungal susceptibility on microdilution and gradient diffusion methods. Internal transcriber spacer sequencing identified Rhodotorula mucilaginosa (n = 12), Rhodotorula toruloides (n = 2), Rhodotorula dairenensis (n = 1), and Cystobasidium minutum (n = 1). Amphotericin B was the most effective drug. A good essential agreement was observed on MIC values of amphotericin B and voriconazole determined by the two methods. Therefore, the gradient method is useful for susceptibility tests of R. mucilaginosa against these drugs.

Rhodotorula spp. in the gut - foe or friend?

Rhodotorula spp. belong to the basidiomyceteous fungi. They are widespread in the environment. Transmission to humans occur mainly through air and food. Intestinal colonization is rather common, but an overgrowth is normally suppressed, since their optimal growth temperature is exceeded in the body. A massive presence in the gut indicates a disturbance of the balance of the microbial flora due to different causes. One particular reason will be the treatment with azoles because this will create an advantage for these azole resistant fungi. First of all, the finding of increased numbers of Rhodotorula in stool specimen is not alarming. In contrast, the colonized human will profit from such a situation since these fungi produce a lot of useful nutrients such as proteins, lipids, folate, and carotinoids. Furthermore, a probiotic effect due to regulation of multiplication of pathogenic bacteria and by neutralizing or destroying their toxins can be anticipated. On the other hand, their massive presence may increase the risk of fungemia and ensuing organ infections especially when the host defense system is hampered. Indeed, Rhodotorula spp. range among the emerging fungal pathogens in the compromised host. However, it can be doubted whether all these opportunistic infections reported originate primarily from the gut.

Cell Envelope Integrity and Capsule Characterization of Rhodotorula mucilaginosa Strains from Clinical and Environmental Sources

Currently, there is very little known about the phenotypic variability within species of Rhodotorula strains and the role of their capsule. Cryptococcus neoformans has been considered the only encapsulated human fungal pathogen, but as more individuals come to live in states of immunocompromised health, they are more susceptible to fungal infections, including those by Rhodotorula. R. mucilaginosa species are some of those most commonly associated with clinical infections. We wanted to know if clinical and environmental strains of R. mucilaginosa demonstrated disparate capsule phenotypes. With limited antifungal options available and clinical Rhodotorula spp. often resistant to common antifungal drugs such as fluconazole, caspofungin (1, 2), and voriconazole (2), a better understanding of the fungal biology could inform the design and use of future antifungal drugs. The generation of an antibody specific to Rhodotorula fungi could be a useful diagnostic tool, and this work presents the first mention of such in the literature.

Rhodotorula yeasts are pink, encapsulated basidiomycetes isolated from a variety of environments and clinical settings. They are increasingly linked with disease, particularly central venous catheter infections and meningitis, in immunocompromised patients. Eight clinical and eight environmental strains molecularly typed as Rhodotorula mucilaginosa were compared to six Cryptococcus neoformans strains for phenotypic variability. Growth on cell integrity-challenging media suggested that R. mucilaginosa cells possess differences in signaling pathways, cell wall composition, or assembly and that their membranes are more susceptible to perturbations than those of C. neoformans. All 16 R. mucilaginosa strains produced urease, while none produced melanin with l-3,4-dihydroxyphenylalanine (l-DOPA) as a substrate. India ink staining reveals that clinical R. mucilaginosa capsules are larger than environmental capsules but that both are generally smaller than C. neoformans capsules. All R. mucilaginosa strains were resistant to fluconazole. Only two clinical strains were susceptible to voriconazole; all of the environmental strains were resistant. We generated an anticapsular antibody (Rh1) to R. mucilaginosa; Rh1 did not bind C. neoformans control strains, was specific to Rhodotorula species, and bound to all tested Rhodotorula strains. Binding assays performed with wheat germ agglutinin (WGA), concanavalin A (ConA), calcofluor white (CFW), and eosin Y dye (EY) cell surface probes suggested that chitin may be more accessible in R. mucilaginosa but that the total abundance of chitooligomers is less than in C. neoformans. This report describes a novel reagent that can be used to identify Rhodotorula species and lays the foundation for future cell envelope composition analysis.

IMPORTANCE Currently, there is very little known about the phenotypic variability within species of Rhodotorula strains and the role of their capsule. Cryptococcus neoformans has been considered the only encapsulated human fungal pathogen, but as more individuals come to live in states of immunocompromised health, they are more susceptible to fungal infections, including those by Rhodotorula. R. mucilaginosa species are some of those most commonly associated with clinical infections. We wanted to know if clinical and environmental strains of R. mucilaginosa demonstrated disparate capsule phenotypes. With limited antifungal options available and clinical Rhodotorula spp. often resistant to common antifungal drugs such as fluconazole, caspofungin (1, 2), and voriconazole (2), a better understanding of the fungal biology could inform the design and use of future antifungal drugs. The generation of an antibody specific to Rhodotorula fungi could be a useful diagnostic tool, and this work presents the first mention of such in the literature.

Characterization of the total and viable bacterial and fungal communities associated with the International Space Station surfaces

BACKGROUND

The International Space Station (ISS) is a closed system inhabited by microorganisms originating from life support systems, cargo, and crew that are exposed to unique selective pressures such as microgravity. To date, mandatory microbial monitoring and observational studies of spacecraft and space stations have been conducted by traditional culture methods, although it is known that many microbes cannot be cultured with standard techniques. To fully appreciate the true number and diversity of microbes that survive in the ISS, molecular and culture-based methods were used to assess microbial communities on ISS surfaces. Samples were taken at eight pre-defined locations during three flight missions spanning 14 months and analyzed upon return to Earth.

RESULTS

The cultivable bacterial and fungal population ranged from 104 to 109 CFU/m2 depending on location and consisted of various bacterial (Actinobacteria, Firmicutes, and Proteobacteria) and fungal (Ascomycota and Basidiomycota) phyla. Amplicon sequencing detected more bacterial phyla when compared to the culture-based analyses, but both methods identified similar numbers of fungal phyla. Changes in bacterial and fungal load (by culture and qPCR) were observed over time but not across locations. Bacterial community composition changed over time, but not across locations, while fungal community remained the same between samplings and locations. There were no significant differences in community composition and richness after propidium monoazide sample treatment, suggesting that the analyzed DNA was extracted from intact/viable organisms. Moreover, approximately 46% of intact/viable bacteria and 40% of intact/viable fungi could be cultured.

CONCLUSIONS

The results reveal a diverse population of bacteria and fungi on ISS environmental surfaces that changed over time but remained similar between locations. The dominant organisms are associated with the human microbiome and may include opportunistic pathogens. This study provides the first comprehensive catalog of both total and intact/viable bacteria and fungi found on surfaces in closed space systems and can be used to help develop safety measures that meet NASA requirements for deep space human habitation. The results of this study can have significant impact on our understanding of other confined built environments on the Earth such as clean rooms used in the pharmaceutical and medical industries.

The Effects of Mentha × piperita Essential Oil on C. albicans Growth, Transition, Biofilm Formation, and the Expression of Secreted Aspartyl Proteinases Genes

The rise in resistance and changes in the spectrum of Candida infections have generated enormous interest in developing new antifungal drugs using natural molecules such as plant essential oils (EOs). Antimicrobial activity against foodborne pathogenic and spoilage microorganisms has been reported for EOs. The goal of this study was to assess the effect of Mentha × piperita essential oil (EO) on C. albicans growth, transition (change from blastospore to hyphae forms), and biofilm formation as well as on the expression of certain virulent genes. We show that whole EO and its vapor attenuated the yeast’s growth, compared to that in the control. The effect of the EO was comparable to that of amphotericin-B (AmB). The EO and its vapor significantly decreased the morphological changes of C. albicans, reduced biofilm formation, and disrupted mature C. albicans biofilms. The effect produced by whole EO on biofilm formation/disruption was notably comparable to that observed with AmB. Exposure of C. albicans to EO and its vapor downregulated the expression of various genes, such as secreted aspartyl proteinases (SAP 1, 2, 3, 9, 10) and hyphal wall protein 1 (HWP1). Altogether, these results provide new insight into the efficacy of Mentha × piperita EO against C. albicans and suggest the potential of Mentha × piperita EO for use as an antifungal therapy in multiple applications.

Stress-Tolerant Yeasts: Opportunistic Pathogenicity Versus Biocontrol Potential

Stress-tolerant fungi that can thrive under various environmental extremes are highly desirable for their application to biological control, as an alternative to chemicals for pest management. However, in fungi, the mechanisms of stress tolerance might also have roles in mammal opportunism. We tested five species with high biocontrol potential in agriculture (Aureobasidium pullulans, Debayomyces hansenii, Meyerozyma guilliermondii, Metschnikowia fructicola, Rhodotorula mucilaginosa) and two species recognized as emerging opportunistic human pathogens (Exophiala dermatitidis, Aureobasidium melanogenum) for growth under oligotrophic conditions and at 37 °C, and for tolerance to oxidative stress, formation of biofilms, production of hydrolytic enzymes and siderophores, and use of hydrocarbons as sole carbon source. The results show large overlap between traits desirable for biocontrol and traits linked to opportunism (growth under oligotrophic conditions, production of siderophores, high oxidative stress tolerance, and specific enzyme activities). Based on existing knowledge and these data, we suggest that oligotrophism and thermotolerance together with siderophore production at 37 °C, urease activity, melanization, and biofilm production are the main traits that increase the potential for fungi to cause opportunistic infections in mammals. These traits should be carefully considered when assessing safety of potential biocontrol agents.

Dermatite fúngica associada à Rhodotorula glutinis em cão - Canis familiaris ): relato de caso

RESUMO O fungo Rhodotorula sp. era considerado como não patogênico, mas, com o aumento de casos de humanos imunossuprimidos nas últimas duas décadas, as espécies R. mucilaginosa, R. glutinis e R. minuta se tornaram agentes potencialmente patogênicos. Poucos relatos clínicos veterinários associados à Rhodotorula spp. foram descritos, e o objetivo deste trabalho foi descrever um caso de dermatite fúngica causada por R. glutinis em cão imunossuprimido devido à leishmaniose visceral e osteossarcoma, na cidade de Cuiabá-Mato Grosso. Um cão, macho, 11 anos, sem raça definida, foi trazido ao Hospital Veterinário apresentando lesões de pele com diagnóstico de dermatofitose e foi prescrito tratamento tópico à base de óleo de melaleuca, sem melhora após um mês de tratamento. O animal retornou ao Hospital Veterinário com hemorragia na região lesionada da cauda, e foi realizada biópsia para exames microbiológico e histopatológico. Nas análises microbiológica e histopatológica, foi isolada uma levedura e detectada a presença de estrutura semelhante a leveduras na coloração de prata, respectivamente. A levedura isolada foi identificada como R. glutinis por meio do sequenciamento do DNA. Um novo tratamento foi instituído, sem melhora do quadro clínico. O animal foi diagnosticado também com leishmaniose e osteossarcoma, provavelmente ocasionando a immunossupressão, e seu quadro evoluiu a óbito.

Polar solar panels: Arctic and Antarctic microbiomes display similar taxonomic profiles

Solar panels located on high (Arctic and Antarctic) latitudes combine the harshness of the climate with that of the solar exposure. We report here that these polar solar panels are inhabited by similar microbial communities in taxonomic terms, dominated by Hymenobacter spp., Sphingomonas spp. and Ascomycota. Our results suggest that solar panels, even on high latitudes, can shape a microbial ecosystem adapted to irradiation and desiccation.

Investigating cross-contamination by yeast strains from dental solid waste to waste-handling workers by DNA sequencing

Trying to widen the discussion on the risks associated with dental waste, this study proposed to investigate and genetically compare yeast isolates recovered from dental solid waste and waste workers. Three samples were collected from workers' hands, nasal mucosa, and professional clothing (days 0, 30, and 180), and two from dental waste (days 0 and 180). Slide culture, microscopy, antifungal drug susceptibility, intersimple sequence repeat analysis, and amplification and sequencing of internal transcribed spacer regions were performed. Yeast strains were recovered from all waste workers' sites, including professional clothes, and from waste. Antifungal susceptibility testing demonstrated that some yeast recovered from employees and waste exhibited nonsusceptible profiles. The dendrogram demonstrated the presence of three major clusters based on similarity matrix and UPGMA grouping method. Two branches displayed 100% similarity: three strains of Candida guilliermondii isolated from different employees, working in opposite work shifts, and from diverse sites grouped in one part of branch 1 and cluster 3 that included two samples of Candida albicans recovered from waste and the hand of one waste worker. The results suggested the possibility of cross‐contamination from dental waste to waste workers and reinforce the need of training programs focused on better waste management routines.

Biofilm formation and antifungal susceptibility of Trichosporon asahii isolates from Mexican patients

BACKGROUND

Trichosporon asahii is a yeast-like fungus that has recently gained importance as a cause of opportunistic systemic infections. The pathogenicity and virulence factors of T. asahii remain largely unknown. Because of the association between invasive infections and the use of catheters and related devices, the ability of the microorganism to adhere and form biofilms may play an important role in the pathogenicity during a trichosporonosis.

AIMS

The aim of this study is to identify an association between biofilm formation by T. asahii isolates and their genotype and/or clinical source.

METHODS

The biofilm production of 49 T. asahii strains isolated from Mexican patients was measured using the crystal violet stain method, and a comparison made with different adhesion phase incubation times. Antifungal susceptibility testing was performed using a modified CLSI protocol coupled with the quantification of the viable cells with the XTT reduction method.

RESULTS

All the T. asahii isolates assayed were able to produce biofilm in vitro, with an intraspecific variability being observed. Overall, increased biofilm production was found when extending the adhesion phase incubation time from 2 to 4h. No association could be established between the biofilm-producing phenotype and either the genotype or clinical source. Higher antifungal resistance to amphotericin B and fluconazole was linked to increased biofilm production by T. asahii.

CONCLUSIONS

All clinical isolates tested were able to produce biofilm. No association could be established between biofilm formation and genotype or clinical source.

Consortia formed by yeasts and acetic acid bacteria Asaia spp. in soft drinks

Yeast strains and acetic acid bacteria were isolated from spoiled soft drinks with characteristic flocs as a visual defect. Polymerase chain reaction and amplification of a partial region of the LSU rRNA gene identified the bacteria as Asaia spp. Sequence analysis of the D1/D2 region of the 26S rDNA in turn identified the yeast isolates as Wickerhamomyces anomalus, Dekkera bruxellensis and Rhodotorula mucilaginosa. The hydrophobicity and adhesion properties of the yeasts were evaluated in various culture media, taking into account the availability of nutrients and the carbon sources. The highest hydrophobicity and best adhesion properties were exhibited by the R. mucilaginosa cells. Our results suggest that Asaia spp. bacterial cells were responsible for the formation of flocs, while the presence of yeast cells may help to strengthen the structure of co-aggregates.

Reversible naftifine-induced carotenoid depigmentation in Rhodotorula mucilaginosa (A. Jörg.) F.C. Harrison causing onychomycosis

Rhodotorula mucilaginosa was isolated from a patient with onychomycosis, and identification was confirmed by morphological and cultural characteristics as well as by DNA molecular analysis. Antifungal agents naftifine (10 mg/mL, active substance in Exoderil) and bifonazole (10 mg/mL, active substance in Canespor) were tested in different concentrations to assess in vitro effects on fungal growth and carotenoid synthesis. The antifungal mechanisms of action of naftifine and bifonazole against R. mucilaginosa isolates were similar and affected the biosynthetic pathway of ergosterol. For the first time, this research demonstrates that naftifine affects the carotenoid biosynthetic pathway, producing depigmentation of R. mucilaginosa in solid and liquid media. Furthermore, depigmentation was a reversible process; naftifine-treated yeast cells that were depigmented resumed carotenoid production upon transfer to fresh media. Raman and UV-vis spectrophotometry in conjunction with chromatographic analysis detected changes in carotenoids in yeast cells, with torulene decreasing and B-carotene increasing after repigmentation. Transmission electron micrographs revealed critical ultrastructural modifications in the depigmented cells after naftifine treatment, i.e., a low-electron-density cell wall without visible mucilage or lamellate structure.

Biofilm Formation by Pseudallescheria/Scedosporium Species: A Comparative Study

Pseudallescheria/Scedosporium species are medically important fungi that are present in soil and human impacted areas and capable of causing a wide spectrum of diseases in humans. Although little is known about their pathogenesis, their growth process and infection routes are very similar to those of Aspergillus species, which grow as biofilms in invasive infections. All nine strains tested here displayed the ability to grow as biofilms in vitro and to produce a dense network of interconnected hyphae on both polystyrene and the surfaces of central venous catheters, but with different characteristics. Scedosporium boydii and S. aurantiacum clinical isolates were able to form biofilms faster than the corresponding environmental strains, as evidenced in kinetic assays for S. boydii and CLSM for S. aurantiacum. Biofilms formed by Pseudallescheria/Scedosporium species had significantly higher resistance to the class of antifungal azole than was observed in planktonic cells, indicating a protective role for this structure. In addition, the clinical S. aurantiacum isolate that formed the most robust biofilms was also more virulent in a larvae Galleria mellonella infection model, suggesting that the ability to form biofilms enhances virulence in Pseudallescheria/Scedosporium species.