Recurrent isolation of an uncommon yeast,Candidapararugosa, from a sarcoma patient

Isolation and identification of Wickerhamiella tropicalis from blood culture by MALDI-MS

Wickerhamiella is a genus of budding yeast that is mainly isolated from environmental samples, and 40 species have been detected. The yeast isolated from human clinical samples usually only contain three species: W. infanticola, W. pararugosa and W. sorbophila. In this study, we isolated W. tropicalis from a blood sample of a six-year-old female with a history of B-cell precursor lymphoblastic leukemia in Japan in 2022. Though the strain was morphologically identified as Candida species by routine microbiological examinations, it was subsequently identified as W. tropicalis by sequencing the internal transcribed spacer (ITS) of ribosomal DNA (rDNA). The isolate had amino acid substitutions in ERG11 and FKS1 associated with azole and echinocandin resistance, respectively, in Candida species and showed intermediate-resistant to fluconazole and micafungin. The patient was successfully treated with micafungin. Furthermore, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) detected three novel peaks that are specific for W. tropicalis, indicating that MALDI-MS analysis is useful for rapid detection of Wickerhamiella species in routine microbiological examinations.

Bloodstream infection caused by Wickerhamiella pararugosa in a patient with intestinal obstruction: A case report

The fungus Wickerhamiella pararugosa (Candida pararugosa) has been detected in various human organs but has rarely caused bloodstream infections. This report presents a case of central venous catheter-related bloodstream infection (CRBSI) of W. pararugosa in an adult. A female patient in her 80s was admitted to our facility for intestinal obstruction caused by colorectal cancer. The patient's ability to consume food was hindered, necessitating the insertion of a central venous catheter (CVC) into the internal jugular vein. On day 3 after admission, the patient developed a fever, prompting blood and CVC tip cultures to be performed. On day 5, yeast-like fungi were discovered in the blood cultures, and fosfluconazole (fluconazole [FLCZ] pro-drug) treatment was initiated. On day 8, yeast-like fungi were identified in both the blood and CVC tip cultures, leading to a diagnosis of CRBSI. The fungus was identified as W. pararugosa through biochemical and genetic characterization. This finding justified the use of micafungin (MCFG) for combination therapy. On day 17, the minimum inhibitory concentrations (MIC) for FLCZ and MCFG were 4-8 and 0.06 μg/mL, respectively. Accordingly, the treatment was changed to monotherapy with MCFG. After a 21-day treatment regimen, the patient was discharged on day 31. We present a case of CRBSI caused by W. pararugosa in an adult with intestinal obstruction. The notable increase in the MIC of FLCZ necessitated monotherapy with MCFG, which resulted in successful recovery of the patient.

Catheter-associated blood stream infections due to Candida pararugosa in a patient with acute myeloid leukemia: A case report

Infections caused by uncommon Candida species have dramatically increased in recent decades, mostly among hematological malignancies. This report aims to present a case of Candida pararugosa bloodstream infection, review previous cases with C. pararugosa infections, and provide a concise review of the clinical background, risk factors, and brief the management of infections. A 3-year-old boy with a history of acute myeloid leukemia was hospitalized in Omid Hospital, Isfahan, Iran. Two consecutive blood cultures were taken from the peripheral vein and port catheter; after that, empirically meropenem was administered. Candida pararugosa were isolated from blood-based on conventional and molecular assays. Furthermore, the antifungal susceptibility profiles of the isolate were determined, which exhibited resistance to fluconazole (8 μg/mL). Antifungal therapy with caspofungin and removing the patient's port led to a significant clinical improvement of the patient's conditions. So far, in the literature review, 10 cases of clinical C. pararugosa isolates were found, of which 5 patients had bloodstream infections. Most patients with C. pararugosa infection presented with specific underlying conditions, such as malignancy, sarcoma, surgery, and adult acute myeloid leukemia. Patients with indwelling catheters run a high risk of acquiring C. pararugosa bloodstream infection. Therefore, special consideration should be given to opportunistic fungal infections in immunocompromised individuals using catheters.

Catheter-Related Sepsis by Candida pararugosa in an Adult Patient under Chemotherapy Regimen

Candida pararugosa is present in animals and humans in different organs and biological liquids, usually as a saprophyte. We report the case of a 61-year-old woman diagnosed with de novo stage IV metastatic lobular breast cancer, carrying a central venous catheter (port-a-cath) and bilateral stents for perirenal infiltration by malignancy. During chemotherapy regimen, a febrile episode occurred, along with a high level of serum glucan. The port-a-cath was removed after blood collection for culture, which gave isolation of Candida pararugosa strains. Given high glucan level and the patient's frailty, empirical treatment with fluconazole was started with load-dose, 800 mg orally, at day 1 and, afterwards, with 400 mg daily for two weeks. The phenotype of susceptibility to antibiotics of the strain demonstrated lower minimal inhibitory concentration to fluconazole than that reported in the literature. The patient remained asymptomatic, and inflammation parameters showed normalization. Unfortunately, three weeks later, meningeal localization of cancer caused rapid deterioration and death.

Revision of the medically relevant species of the yeast genus Diutina

Diutina (Candida) rugosa is emerging as a causative agent of human infections. Recently some close relatives have been described, that is, D. mesorugosa, D. pseudorugosa, and D. neorugosa, some of which have also been implicated in human infection. Phylogenetic relationships of 24 clinical isolates of the D. rugosa complex are reconstructed using multilocus sequence analysis of five housekeeping genes, supplemented with phenotypic studies of CandiSelect™ 4 Agar and nutritional physiology. Diutina mesorugosa could not meaningfully be distinguished from D. rugosa and is regarded as a synonym. Diutina neorugosa and D. pseudorugosa represent separate, distantly related species within the genus Diutina, but have as yet not been encountered in clinical settings.

Candida pararugosa: First Reported Bloodstream Infection in an Adult

Candida pararugosa is a yeast that has been previously isolated in various human specimens. The first reported isolation was from human feces in 1998, with subsequent reports of positive cultures from the oral cavity where it was thought to represent colonization rather than true infection. Though it has been isolated from other human sites, its clinical significance and manifestations are poorly characterized. We report the case of a 39-year-old woman on parenteral hyperalimentation who developed post abdominal surgery sepsis and surgical wound necrotizing fasciitis. Candida pararugosa was isolated from two different blood cultures and the patient's clinical status improved after initiation of therapy with micafungin. Though it was not clear whether sepsis was driven by the candidemia or the necrotizing fasciitis or both, this report appears to be the first case of Candida pararugosa bloodstream infection described in an adult.

Native Killer Yeasts as Biocontrol Agents of Postharvest Fungal Diseases in Lemons

Economic losses caused by postharvest diseases represent one of the main problems of the citrus industry worldwide. The major diseases affecting citrus are the "green mold" and "blue mold", caused by Penicillium digitatum and P. italicum, respectively. To control them, synthetic fungicides are the most commonly used method. However, often the emergence of resistant strains occurs and their use is becoming more restricted because of toxic effects and environmental pollution they generate, combined with trade barriers to international markets. The aim of this work was to isolate indigenous killer yeasts with antagonistic activity against fungal postharvest diseases in lemons, and to determine their control efficiency in in vitro and in vivo assays. Among 437 yeast isolates, 8.5% show to have a killer phenotype. According to molecular identification, based on the 26S rDNA D1/D2 domain sequences analysis, strains were identified belonging to the genera Saccharomyces, Wickerhamomyces, Kazachstania, Pichia, Candida and Clavispora. Killers were challenged with pathogenic molds and strains that caused the maximum in vitro inhibition of P. digitatum were selected for in vivo assays. Two strains of Pichia and one strain of Wickerhamomyces depicted a significant protection (p <0.05) from decay by P. digitatum in assays using wounded lemons. Thus, the native killer yeasts studied in this work showed to be an effective alternative for the biocontrol of postharvest fungal infections of lemons and could be promising agents for the development of commercial products for the biological control industry.

Biosynthesis of single-cell biomass from olive mill wastewater by newly isolated yeasts

The aim of this study was to assess the potential of newly isolated yeast strains Schwanniomyces etchellsii M2 and Candida pararugosa BM24 to produce yeast biomass on olive mill wastewater (OMW). Maximum biomass yield was obtained at 75% (v/v) OMW, after 96 h of incubation at 30 °C and 5% (v/v) inoculum size. The optimal carbon/nitrogen (C/N) ratio was in the range of 8:1 to 10:1, and ammonium chloride was selected as the most suitable nitrogen source. Under these conditions, a maximum biomass production of 15.11 and 21.68 g L(-1) was achieved for Schwanniomyces etchellsii M2 and Candida pararugosa BM24, respectively. Proteins were the major constituents of yeast cells (35.9-39.4% dry weight), lipids were 2.8-5% dry weight, and ash ranged from 4.8 to 9.5 % dry weight. Besides biomass production, yeast strains were also able to reduce toxicity and polluting parameter levels of the spent OMW-based medium. The practical results presented show that pH rose from initial value of 5.5 to 7.24-7.45 after fermentation. Approximately 23.1-41.4% of the chemical oxygen demand (COD) and 15.4-19.2% of the phenolic compounds were removed. The removal of phenolic compounds was associated with their biodegradation and their partial adsorption on yeast cells.

Comparison of the accuracy of two conventional phenotypic methods and two MALDI-TOF MS systems with that of DNA sequencing analysis for correctly identifying clinically encountered yeasts

We assessed the accuracy of species-level identification of two commercially available matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems (Bruker Biotyper and Vitek MS) and two conventional phenotypic methods (Phoenix 100 YBC and Vitek 2 Yeast ID) with that of rDNA gene sequencing analysis among 200 clinical isolates of commonly encountered yeasts. The correct identification rates of the 200 yeast isolates to species or complex (Candida parapsilosis complex, C. guilliermondii complex and C. rugosa complex) levels by the Bruker Biotyper, Vitek MS (using in vitro devices [IVD] database), Phoenix 100 YBC and Vitek 2 Yeast ID (Sabouraud's dextrose agar) systems were 92.5%, 79.5%, 89%, and 74%, respectively. An additional 72 isolates of C. parapsilosis complex and 18 from the above 200 isolates (30 in each of C. parapsilosis, C. metapsilosis, and C. orthopsilosis) were also evaluated separately. Bruker Biotyper system could accurately identify all C. parapsilosis complex to species level. Using Vitek 2 MS (IVD) system, all C. parapsilosis but none of C. metapsilosis, or C. orthopsilosis could be accurately identified. Among the 89 yeasts misidentified by the Vitek 2 MS (IVD) system, 39 (43.8%), including 27 C. orthopsilosis isolates, could be correctly identified Using the Vitek MS Plus SARAMIS database for research use only. This resulted in an increase in the rate of correct identification of all yeast isolates (87.5%) by Vitek 2 MS. The two species in C. guilliermondii complex (C. guilliermondii and C. fermentati) isolates were correctly identified by cluster analysis of spectra generated by the Bruker Biotyper system. Based on the results obtained in the current study, MALDI-TOF MS systems present a promising alternative for the routine identification of yeast species, including clinically commonly and rarely encountered yeast species and several species belonging to C. parapsilosis complex, C. guilliermondii complex, and C. rugosa complex.

Diversity of fungal flora in raw milk from the Italian Alps in relation to pasture altitude

The present paper explores the diversity of mycobiota inhabiting raw milk sampled at different altitudes (1400 m, 1800 m, 2200 m) from cows grazing Alpine pastures of Valle d’Aosta (North-Western Italian Alps). To this aim, multilocus sequencing was performed at barcodes commonly used for fungal identification (ITS1, D1/D2 domains of the 26S rRNA gene, and part of the β-tubulin gene). A total of 31 species were detected, most of them yeasts, followed by moulds and by 2 sequences of macroscopic fungi. Several yeasts and moulds were well-characterized inhabitants of the dairy environment, known to positively contribute to cheesemaking. Among these, Candida was the most represented genus with a tendency to cluster at the highest altitudes (6 over 8 observations at ≥ 1800 m), and Kluyveromyces marxianus the most abundant single species, retrieved at all altitudes. The environmental ascomycetous Atrotorquata lineata, never put in relation with food nor described outside North-America, was another species among those most frequently retrieved and was detected in 6 milks at 1400 and 1800 m. The remaining fungi, in general never reported in milk, were mostly environmental. Many of them resulted associated with plants as pathogens or symbionts. Finally, the highest sampled altitude yielded a significant fungal diversity (17 species). This work enlarges the knowledge of fungal consortia inhabiting raw milk and introduces microbial ecology among the altitude-dependent factors, in the composition of Alpine pastures, with the potential of shaping the properties of milks and cheeses, together with the already described physical, chemical and botanical variables.

Molecular identification and antifungal susceptibility testing of clinical isolates of the Candida rugosa species complex and proposal of the new species Candida neorugosa

Candida rugosa is a poorly known fungal species occasionally involved in human infections. A molecular analysis of the sequences of the D1/D2 domains and the internal transcribed spacer (ITS) region of the ribosomal genes of 24 clinical isolates phenotypically identified as C. rugosa demonstrated that only 10 (41.6%) isolates belonged to that species. The other isolates were identified as Candida pararugosa (41.6%) and Candida pseudorugosa (8.3%). The remaining two isolates, from human and equine infections, respectively, were clearly different from the others and represent a new species proposed here as Candida neorugosa. The closest species by D1/D2 sequences was the type strain of C. rugosa, with only 92.3% similarity. C. neorugosa can also be differentiated from all other species of the C. rugosa complex by phenotypic features. The eight antifungal drugs tested showed high in vitro activity against the 24 isolates included in the study.