Search Results (117)

Silage is a core roughage resource for ruminant production, but aerobic deterioration caused by microorganisms severely reduces its nutritional value and increases microbial risk. This study aimed to isolate and identify specific spoilage organisms (SSOs) from Napier grass silages during aerobic deterioration and evaluate their spoilage capability. Based on morphological observation, physiological and biochemical tests, and ITS rDNA sequence analysis, four SSOs were obtained as Trichosporon asahii (TA32), Nakaseomyces glabratus (NG38), Candida tropicalis (CT39), and Pichia kudriavzevii (PK41) with high lactate-assimilating and spoilage capacity. All four strains were facultative anaerobic yeast and exhibited robust growth within the range of 25–40 °C and pH 3.5–6.5. To verify their spoilage capability, these purified strains were inoculated into Napier grass silage and exposed to air. Fermentation and chemical parameters were monitored at 0, 2, 5, and 9 days. Results showed that silages inoculated with PK41 or TA32 exhibited the lowest aerobic stability with most rapid increase in pH (p < 0.05), while the control (CON) remained the highest aerobic stability (p < 0.05). These results provide a theoretical basis for developing targeted preservation technologies to extend the shelf-life of silage. Full article

The aim of this work was to identify the microbial agent(s) responsible for a structural defect in Provolone Valpadana, Protected Designation of Origin (PDO) cheese, and to establish their spread along the production line. Repeated sampling of defective cheeses and analyses of processing intermediates following two inspections at the cheese factory identified yeasts as the main causative agents. Microbiological analysis highlighted an almost constant presence of yeasts, which dominate over the other microbial groups. Forty yeast isolates from defective cheeses were identified by sequencing the D1/D2 region of the 26S rRNA gene. Saccharomyces cerevisiae, Kluyveromyces marxianus, and Debaryomyces hansenii dominated in all sampled cheeses, followed by D. tyrocola, Pichia kudriavzevii, and Torulaspora delbrueckii. Yeast and bacterial metabarcoding on three cheeses with a yeast count > log 4.0 CFU/mL indicated D. hansenii as the dominant yeast taxon and confirmed the absence of gas-producing bacterial taxa. RAPD-PCR analysis suggested the presence of yeast biofilms in the dairy environment or along the production line, as confirmed by the repeated isolation of specific genotypes of S. cerevisiae, K. marxianus, and D. hansenii in different defective cheeses sampled between April and August 2023, as well as in samples taken following two inspections at the production site, during cheese processing and ripening. Full article

Background: Community-onset fungemia is a clinically significant syndrome frequently linked to recent healthcare exposure and significant morbidity and mortality. Methods: We performed a 21-year, single-centre retrospective cohort of consecutive yeast bloodstream infections diagnosed at the Emergency Department (2004–2024). Clinical/epidemiological data, species identification (MALDI-TOF MS), antifungal susceptibility (CLSI M27; Sensititre YO10), and whole-genome sequencing (WGS) were analyzed. Results: Forty-eight episodes (51 isolates) were included; 56.3% were male, median age 74 years (IQR 63–82). Acquisition was healthcare-associated in 38/48 (79.2%). Sources were unknown (36.7%), abdominal (22.4%), urological (22.4%), catheter-related (14.3%), and 2.1% was attributed to a cardiovascular and a joint focus; 18.8% were polymicrobial. Crude mortality was 20.8% at 7 days (10/48) and 29.2% at 30 days (14/48). Species distribution: Candida albicans 41.2%, Nakaseomyces glabratus 27.5%, Candida parapsilosis 11.8%, Candida tropicalis 11.8%, Pichia kudriavzevii 3.9%, Clavispora lusitaniae 1.9%, and Candida orthopsilosis 1.9%. No isolate was resistant to anidulafungin, micafungin, or amphotericin B; one N. glabratus showed reduced susceptibility to caspofungin. Azole resistance was observed in one C. albicans and one N. glabratus isolate. WGS (44 isolates) confirmed MALDI-TOF identifications and characterized resistance markers. All 12 sequenced N. glabratus carried ERG2 I207V, PDR15/PDH1 E839D, and PDR1 V91I/L98S. Notable cases included one N. glabratus caspofungin-intermediate with FKS2 F659C, N. glabratus fluconazole-resistant with multiple PDR1 substitutions including a unique novel G857V, and C. albicans fluconazole-resistant harbouring alterations in MRR1/MRR2, CDR1, and ERG11. Conclusions: In this 21-year cohort, community-onset fungemia was predominantly healthcare-associated, with C. albicans as the predominant species, followed by N. glabratus. Crude mortality reached 29.2% at 30 days. Echinocandin resistance was not observed; azole resistance was uncommon. WGS provided precise speciation and actionable insight into resistance mechanisms, including a putatively novel PDR1 G857V in N. glabratus. Full article

Candida krusei empyema is a rare but serious manifestation of invasive candidiasis, characterized by intrinsic resistance to fluconazole, biofilm formation, and high mortality, with limited case-level data to inform management. This review aims to systematically identify and synthesize all reported English-language cases of Candida krusei empyema from January 2005 to June 2025 using PubMed, ScienceDirect, OVID MEDLINE, and Gale OneFile and perform descriptive analysis on them. Screening, data extraction, and eligibility assessment were performed, and those articles not clearly meeting eligibility criteria were reviewed by additional reviewers with consensus resolution. Seven publications (six individual cases and two cohorts) were included. We additionally describe the clinical course, management, and outcome of a 70-year-old bilateral lung transplant patient who developed persistent C. krusei empyema despite optimized antifungal therapy. Patients ranged from 11 to 74 years of age (median 62.5 years). Predisposing factors included esophageal perforation (n = 4), post-transplant hemorrhage (n = 1), community-acquired empyema (n = 1), and thoracic surgery (n = 1). Empiric fluconazole was switched to caspofungin (3/4), with others receiving amphotericin B, voriconazole, or combination therapy. Source control varied: chest tube drainage (n = 3), percutaneous catheter (n = 3), and surgical decortication (n = 2). Mortality was 14.3% (1/7). In the absence of clear guidelines and robust literature, the management approach remains heterogeneous. Optimal care requires early recognition, aggressive multimodal antifungal therapy, and effective source control tailored to patient risk. Standardized antifungal protocols and larger case series are needed to guide clinicians in managing this challenging infection. Full article

This study characterised the diversity of filamentous fungi and yeasts during Malbec grape fermentation in the Southern Oasis of Mendoza (Argentina) winegrowing region, under different sanitary conditions and SO₂ treatments, using morphological and ITS-RFLP-based molecular methods. Alternaria, Cladosporium and Penicillium were present in both sound and damaged grapes, while Aspergillus and Botrytis were primarily found in damaged grapes. The predominant yeast species in both sound and damaged grape must, at lower and higher maturity levels, were Aureobasidium pullulans and Hanseniaspora spp. At higher grape ripening levels species diversity increased, with Hanseniaspora vineae, Metschnikowia pulcherrima and Candida membranifaciens dominating, and others such as Pichia kudriavzevii and Issatchenkia terricola appearing. A. pullulans and M. pulcherrima were highly tolerant to SO₂. Notably, the species Meyerozyma guilliermondii, Zygoascus hellenicus and Hanseniaspora uvarum were exclusively present in damaged grape must, while Zygosaccharomyces bailii was also found in sound grape must. Hanseniaspora spp. and P. kudriavzevii predominated at mid-fermentation and persisted at the end of the process, highlighting their resistance to wine conditions and their potential to influence post-fermentative dynamics. These findings emphasise the significant influence of grape sanitary status on mycobiota composition, with important implications for fermentation behaviour and final wine quality. Full article

(1) Background: Fungal infections of amniotic fluid, especially those caused by Candida spp., are rare but clinically important, as they can be correlated with preterm birth and poor neonatal outcomes. The aim of this study was to assess the antifungal susceptibility of Candida spp. isolated from amniotic fluid using an MIC (minimum inhibitory concentration)-based assay. (2) Methods: Forty consecutive, exploratory Candida isolates were identified from amniotic fluid samples at the “Cuza Vodă” Clinical Hospital of Obstetrics and Gynecology, Iași, and were analyzed successively using Sabouraud agar, the VITEK^® 2 Compact system, and real-time PCR (RT-PCR). (3) Results: C. albicans was the most abundant species (67.5%), followed by Pichia kudriavzevii, Nakaseomyces glabratus, C. parapsilosis, and C. dubliniensis. Fluconazole resistance was observed in two C. albicans isolates, emphasizing the clinical importance of routine antifungal susceptibility testing, and all C. albicans isolates were resistant to micafungin, while amphotericin B remained effective against all isolates. RT-PCR confirmed the presence of C. albicans DNA. (4) Conclusions: The detection of resistant Candida strains highlights the importance of conducting assessments at the species level, which could help clinicians to ensure better antifungal stewardship. Full article

Microorganisms are crucial for the liquor brewing process and substantially impact liquor flavour and quality; therefore, understanding microbial succession is necessary. Most studies use a single-method approach and fail to provide an in-depth analysis. We aimed to combine traditional culture method with high-throughput sequencing (HTS) to identify the microbial diversity and succession in Luzhou-flavour fermentation. HTS revealed 932 bacterial and 980 fungal operational taxonomic units. 16S rDNA, 26S D1/D2 rDNA, and ITS v4/v5 isolated and identified 256 bacterial and 130 yeast strains. Population succession analysis showed that the dominant populations were yeasts, Lactobacillus, and Bacillus (early stage), and yeasts and Lactobacillus (late stage). Lactobacillus, Pichia, Bacillus, and Candida were abundant among all three layers of fermented grains. However, C. ethanolica, Saccharomycetes sp., and an unidentified Saccharomyces cerevisiae were more abundant in the lower layer than in the middle and upper layers, while L. parabuchneri, Oceanobacillus oncorhynchi, and Thermoactinomyces sp. were present only in the lower layer. Correlations among enzyme activity, volatile production, and dominant microbes during fermentation indicated that P. fermentans, L. suebicus, L. acetotolerans, P. kudriavzevii, P. exigua, and B. tequilensis were significantly affected during brewing. Our results lay a foundation for elucidating the microbial fermentation mechanism of Luzhou-flavour liquor and will assist in improving traditional liquor brewing quality and efficiency. Full article

Potentially probiotic yeasts isolated from foodstuffs can be used as components in functional fermented beverages. To date, there have been no reports on the use of Saccharomyces cerevisiae var. boulardii, Pichia kudriavzevii, Metschnikowia pulcherrima, or Hanseniaspora uvarum isolates in the production of a traditional Polish beverage called underbeer (podpiwek). The aim of the study was to determine the usefulness of six isolates of the above-mentioned species as starter cultures for the fermentation of underbeer. First, the important characteristics of the yeasts, like ethanol tolerance and H₂S production, were examined. In the next stage, the wort was fermented by the tested yeasts, and cell viability, fermentation vigor, sugar assimilation, and production of metabolites, as well as properties of the beverage (pH, titratable acidity, color, and turbidity), were determined. Saccharomyces yeasts tolerated the addition of ethanol up to 16% (v/v), while Pichia, Metschnikowia, and Hanseniaspora tolerated up to 10% (v/v) ethanol, and all except H. uvarum produced H₂S. The yeasts remained viable in the beverages for 1 month at the required level, utilized glucose, fructose and partially complex carbohydrates, and produced ethanol (S. cerevisiae, P. kudriavzevii, and M. pulcherrima) and organic acids such as tartaric, malic, and citric acid. The underbeers became sour and showed varying turbidity and a color corresponding to pale-amber beers. All tested strains produced fermented beverages that were low- or non-alcoholic with different properties. This experiment may be a starting point for research into regional products as probiotic or synbiotic foods; however, further research is required for selection of the best strains for underbeer fermentation. Full article

Candidemia is a highly prevalent invasive fungal infection caused primarily by C. albicans, C. parapsilosis, C. glabrata (currently Nakaseomyces glabratus), C. tropicalis, and C. krusei (currently Pichia kudriavzevii). Risk factors for the development of candidemia include steroid-induced immunosuppression used in solid organ or hematopoietic transplantation, and neutropenia secondary to infectious or tumorous processes. Alterations in the gut microbiota in people living with HIV, caused by antiretroviral therapy, increase the possibility of colonization by C. albicans. Likewise, the presence of a central venous catheter, parenteral nutrition, and abdominal surgery stand out as the main risk factors for the development of candidemia. New diagnostic tools have been developed for the diagnosis of this mycosis that allow the identification of the main species, from improvements in conventional stains such as calcofluor white, which increases sensitivity, as well as technologies such as T2 Candida, MoiM assay, biomarker panel (1,3 β-D-glucan, C-reactive protein, presepsin, and procalcitonin), and, more recently, the development of biosensors for the identification of Candida spp. Regarding treatment, the use of micafungin and anidulafungin in patients with obesity defined by a BMI > 30 kg/m² has shown higher survival rates and therapeutic success. Meanwhile, newer antifungals such as rezafungin and fosmanogepix have demonstrated excellent results in the treatment of these patients. Therefore, this review aims to update the epidemiology and risk factors of candidemia, as well as analyze the diagnostic tools and treatments currently available. Full article

Public health in a densely populated city is inextricably linked to the state of the urban environment. The microclimate, the condition of water sources and sanitary well-being are just some of the many environmental factors that have a strong influence on people’s health. The presence of urban green spaces and various birds in cities is extremely important, also to create a more favorable psychological atmosphere for the people who live and/or work there. At the same time, it should not be forgotten that the feces of synanthropic birds are a favorable environment for various potentially pathogenic species of microorganisms, including yeasts of the genus Candida. Here, we investigated the culturable, potentially pathogenic ascomycetous yeast microbiome in the fresh and dry feces of five synanthropic birds (Rock Pigeon, European Starling, White Wagtail, Great Tit and House Sparrow). The samples were collected in spring (May 2024). In total, 48 Rock Pigeon, 47 European Starling, 38 White Wagtail, 32 Great Tit and 30 House Sparrow droppings were collected and analyzed. The selective medium Brilliance Candida Agar was used for cultivation. A total of 638 strains were isolated belonging to 9 yeast species (Arxiozyma bovina, Candida albicans, Nakaseomyces glabratus, Clavispora lusitaniae, C. tropicalis, C. parapsilosis, Pichia kudriavzevii, Debaryomyces hansenii and D. fabryi). All detected yeast species were molecularly identified using the ITS rDNA region. The microbiome of potential pathogens in fresh feces proved to be significantly host-dependent. Most pathogenic yeasts (7 species)—A. bovina, C. albicans, N. glabratus, Cl. lusitaniae, C. tropicalis, C. parapsilosis and P. kudriavzevii—were only detected in fresh feces from pigeons. This list contains five out of six ascomycetous species from the list of critical, high and medium-important yeast pathogens published in the World Health Organization fungal list. Of the potentially pathogenic yeasts, two species were observed in the dry droppings of various birds: C. parapsilosis and P. kudriavzevii. No significant differences in the diversity of culturable pathogens in dry droppings were observed between the different hosts. Fresh droppings from synanthropic birds, especially pigeons (and to a lesser extent dry droppings), therefore pose a health risk. In this study, we did not find any feces from synanthropic birds in which potentially pathogenic ascomycetous yeasts were not detected. To maintain the sanitary safety and well-being of citizens, it is very important to regulate the number of synanthropic birds (primarily pigeons), especially in sensitive areas such as playgrounds, hospital territories, etc. Full article

High-acidity fruit wines, such as sea buckthorn wine, are valued for their nutritional benefits but often suffer from excessive tartness and limited aroma complexity, which restrict their consumer acceptance. The application of non-Saccharomyces yeasts with acid tolerance and flavor-enhancing potential offers a promising strategy to address these challenges. In this study, a highly acid-tolerant yeast strain, Pichia kudriavzevii GAAS-JG-1, was isolated from a naturally fermented apricot system and systematically characterized in terms of its taxonomy, physiological properties, and fermentation potential. The experimental results demonstrated that Pichia kudriavzevii GAAS-JG-1 maintained robust growth activity (OD₆₀₀ = 1.18 ± 0.09) even under extremely acidic conditions (pH 2.0). Furthermore, the strain exhibited a strong tolerance to high ethanol concentrations (16%), elevated sugar levels (350 g/L), and substantial sulfur dioxide exposure (500 mg/L). Optimal growth was observed at 35 °C (OD₆₀₀ = 2.21 ± 0.02). When co-fermented with Saccharomyces cerevisiae in sea buckthorn wine, the ethyl acetate content increased significantly from 303.71 μg/L to 4453.12 μg/L, while the ethyl propionate levels rose from 5.18 μg/L to 87.75 μg/L. Notably, Pichia kudriavzevii GAAS-JG-1 also produced novel flavor compounds such as methyl acetate and ethyl 3-methylthiopropionate, which were absent in the single-strain fermentation. These findings highlight the potential of Pichia kudriavzevii GAAS-JG-1 as a valuable non-Saccharomyces yeast resource with promising applications in the fermentation of high-acidity specialty fruit wines. Full article

Microbiological quality control in cosmetic and pharmaceutical products is crucial for consumer safety. Traditional culture-based detection methods, such as plating on selective media, are time-consuming and may lack sensitivity. Fluorescence In Situ Hybridisation (FISH), a molecular and culture-independent technique, enables rapid and precise microbial identification by targeting specific RNA or DNA sequences with fluorescent probes. In this study, a novel DNA-FISH probe was developed for the detection of Candida albicans in cosmetic formulations. The probe’s specificity was assessed in silico and experimentally using flow cytometry (flow-FISH) on C. albicans and non-target microorganisms, including Pichia kudriavzevii, commonly known as Candida krusei, Saccharomyces cerevisiae, Wickerhamomyces anomalus, Escherichia coli, and Staphylococcus aureus. The probe exhibited 98.9% hybridization efficiency with C. albicans, yielding a fluorescence intensity (FI) of 25,000 (a.u.), while non-target yeasts demonstrated minimal hybridization (4.7%, 2.3%, and 1.9% for C. krusei, S. cerevisiae, and W. anomalus, respectively) and bacteria showed negligible FI. Additionally, the probe’s applicability was evaluated in a tonic formulation, where C. albicans’ hybridization efficiency was slightly reduced to 88.4%, suggesting that formulation components may influence probe performance. Nevertheless, the probe maintained high specificity and efficiency without formamide, a toxic reagent commonly used in FISH. These findings highlight the potential of FISH probes for rapid, accurate, and safe microbial detection, offering a valuable tool for microbiological quality control in the cosmetics industry. Full article

Yeasts isolated from fermented plant-based sources—boza, pickles, and chickpeas—were evaluated for probiotic potential. Among 18 colonies, seven isolates showing no hemolytic activity were selected and identified: Pichia kudriavzevii (four isolates), Kazachstania exigua, Hanseniaspora uvarum, and Saccharomyces cerevisiae. Most isolates were able to survive under low pH and bile salt conditions, simulating the environment of the gastrointestinal tract (5.62–8.59 log CFU/mL) and tolerated NaCl concentrations up to 6–8% (w/v). All isolates exhibited antibiotic resistance; however, their susceptibility to antifungals varied. While P. kudriavzevii DD_B_M88 exhibited the highest hydrophobicity (63.07%), isolate auto-aggregation increased to 53–95% after 24 h. Most isolates showed a great capability to co-aggregate with pathogens and inhibited them significantly (up to 98.72%), except for S. cerevisiae DD_NB_M90. The selected three isolates and their cell-free supernatants, up to a certain concentration, showed no significant cytotoxicity on Caco-2 cell line. Eventually, six isolates, excluding S. cerevisiae DD_NB_M90, fulfilled the probiotic criteria, and can serve as probiotic starter cultures for alternative food production. Full article

This study employed shotgun metagenomics to investigate microbial dynamics, phage-bacteria interactions, and functional genes throughout a three-month apple vinegar fermentation process. A total of 5621 microbial species were identified, revealing three distinct phases: (i) Enterobacteria and non-Saccharomyces species dominated the initial substrate; (ii) S. cerevisiae and Leuconostoc pseudomesenteroides prevailed in the intermediate phase; and (iii) acetic acid bacteria (Acetobacter ghanesis and Gluconobacter spp.), alongside non-Saccharomyces species (Pichia kudriavzevii and Malassezia restricta), dominated the final stages. Bacteriophage analysis revealed the presence of phages targeting spoilage bacteria, such as Pseudomonas and Erwinia, suggesting a role in regulating microbial stability and enhancing fermentation control. Functional metagenomic analysis highlighted key pathways associated with microbial growth and metabolite production, including carbohydrate and amino acid metabolism, energy production, and glycan biosynthesis. Enzymes involved in stress adaptation and secondary metabolism, including oxidative phosphorylation and phenolic compound synthesis, demonstrated microbial resilience and their potential role in shaping the product’s sensory and functional properties. Moreover, Enterobacteriaceae species were associated with pectin degradation during the early stages, aiding substrate breakdown. These findings are crucial for microbial and phage management in fermentation technology, offering valuable insights for innovation in the vinegar industry. Full article

With rising multidrug-resistant yeast pathogens, conventional antifungals are becoming less effective, urging the need for adjuvants that enhance their activity at lower doses. This study evaluated the synergistic activity of antimicrobial peptidomimetics (TM8 and RK758) or colistin sulphate in combination with conventional antifungals against Candida albicans, C. tropicalis, C. parapsilosis, Meyerozyma guilliermondii, Nakaseomyces glabratus, Pichia kudriavzevii and Kluyveromyces marxianus, and Candidozyma auris using the checkerboard microdilution test. RK758 was synergistic with fluconazole in 78% of isolates, with the remaining 22% of isolates still showing partial synergy; it showed synergy with amphotericin B in 56% of isolates, and with caspofungin, 78% of isolates exhibited either synergy or partial synergy. TM8 showed synergy with fluconazole in 44% (with partial synergy in another 44%) of isolates, with amphotericin B in 67% of isolates, and with caspofungin in 44% (with partial synergy in another 44%) of isolates. Colistin with fluconazole or caspofungin exhibited synergy or partial synergy in 56% of the isolates. No antagonism was observed in any of the combinations. Additionally, a time-kill assay further demonstrated synergistic activity between fluconazole and TM8 or RK758. The effects of these peptidomimetics on cell membrane integrity were demonstrated in an ergosterol binding assay, supported by SYTOX Green and cellular leakage assays, both indicating a lytic effect. These results suggest that peptidomimetics can synergise with conventional antifungals, offering a potential strategy for combination therapy against yeast infections. The membrane lytic activity of the peptidomimetics likely plays a role in their synergistic interaction with antifungals, thereby enhancing the antimicrobial activities of both compounds at sub-MIC levels. Full article