Wickerhamomyces Anomalus Research Articles

Esterase profiling and molecular identification of yeasts isolated from different environmental samples from Morocco

One hundred and six fungal strains were isolated from different environmental samples (fresh olive oil cake, exhausted olive oil cake, black olive, rancid butter samples, rotten bread and Roquefort) collected from the region of Meknes, Morocco (coordinates: 33°53′42″N 5°33′17″W). Yeast isolates were tested for their esterase production ability using a qualitative method based on Tween agar plate assay. Enzymatic activity was also confirmed by a quantitative method relying on esterase production in liquid medium (6 days at 28°C with shaking). Molecular characterization of the selected esterase-producing yeasts was performed by sequencing the internal transcribed spacer 1 (ITS1), 5.8S and ITS2 region of the rDNA. A total of five different species were identified in this study: Candida aaseri (LE.26, LE.27 and LE.31 strains), Wickerhamomyces anomalus (LE.106, LE.112 and LE.115 strains), Metschnikowia rancensis (LE.153 strain), Pichia sp., (LE.102) and Rhodotorula mucilaginosa (LE.171 strain). Esterase production in C. aaseri and W. anomalus was found to be straindependent, while for M. rancensis this represents the first study reporting this species as an esterase producer.

Selection of Native Non-Saccharomyces Yeasts with Biocontrol Activity against Spoilage Yeasts in Order to Produce Healthy Regional Wines

Two major spoilage yeasts in the wine industry, Brettanomyces bruxellensis and Zygosaccharomyces rouxii, produce off-flavors and gas, causing considerable economic losses. Traditionally, SO2 has been used in winemaking to prevent spoilage, but strict regulations are in place regarding its use due to its toxic and allergenic effects. To reduce its usage researchers have been searching for alternative techniques. One alternative is biocontrol, which can be used either independently or in a complementary way to chemical control (SO2). The present study analyzed 122 native non-Saccharomyces yeasts for their biocontrol activity and their ability to be employed under fermentation conditions, as well as certain enological traits. After the native non-Saccharomyces yeasts were assayed for their biocontrol activity, 10 biocontroller yeasts were selected and assayed for their ability to prevail in the fermentation medium, as well as with respect to their corresponding positive/negative contribution to the wine. Two yeasts that satisfy these characteristics were Wickerhamomyces anomalus BWa156 and Metschnikowia pulcherrima BMp29, which were selected for further research in application to mixed fermentations.

Ethanol production in switchgrass hydrolysate by ionic liquid-tolerant yeasts

Lignocellulose pretreatment with ionic liquids (IL) enables release of fermentable sugars at yields suitable for biofuel production. However, despite extensive washing, residual IL such as 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]) is harmful to microbes and enzymes involved in downstream processes. Ionic liquid-pretreated switchgrass hydrolysate contains from 0.2 to 4% (w/v) residual [C2C1Im][OAc] depending on the extent of water washing. A total of 25 yeast strains including four commercial ethanologenic Saccharomyces cerevisiae strains were tested to grow and ferment sugars in stepwise screening tests, and ethanol production was measured by GC-FID. Four yeast strains produced >10 g/L ethanol in laboratory media containing [C2C1Im][OAc]. The highest ethanol yield of 70% of theoretical yield was achieved by Wickerhamomyces anomalus UCDFST 72-248 when grown in hydrolysate with 3.2% residual IL. The robust growth and ethanol production by this wild (non-GMO) yeast, together with general stress tolerance of the species, suggests further exploration for biotechnology applications.

Use of selected yeast starter cultures in industrial-scale processing of brined Taggiasca black table olives

The aim of this study was to evaluate the effects of six selected yeast starters on natural Taggiasca black table fermentations, in different brine solutions. The olives were subjected to fermentation in 8% (w/v) NaCl, 12% (w/v) NaCl and 12% (w/v) NaCl brine solutions with 0.3% (w/v) citric acid and inoculated with selected yeast starter strains belonging to the following species: Candida adriatica 1985, Candida diddensiae 2011, Cyteromyces matritensis 2005, Nakazawaea molendini-olei 2004, Saccharomyces cerevisiae 2046 and Wickerhamomyces anomalus 1960. Samples of brines and olives were analysed in the initial phase, then again after 30 and 120 days of fermentation. The yeast starters survived differently during the first 30 days of brine fermentation, depending on the NaCl concentration. After 120 days of fermentation N. molendini-olei 2004 and C. matritensis 2005 failed in the brines with 12% NaCl, while the yeast starter cultures C. diddensiae 2011, C. adriatica 1985 and W. anomalus 1960 showed the best performances in terms of survival and competitiveness towards wild yeasts of the brines. The physicochemical and sensorial analysis suggest a potential positive role of these yeasts during the debittering process of the Taggiasca table olives. Considering the combination between yeast starters and the fermentation conditions, the best indication occurred with the brines containing 12% NaCl acidified with citric acid.

Improvement of the aroma of lily rice wine by using aroma-producing yeast strain Wickerhamomyces anomalus HN006

A fruity aroma-producing yeast strain was isolated with the aim of improving the aroma of fermented lily rice wine, and identified as Wickerhamomyces anomalus HN006. In addition, the effects of adding solid residues of previous fermentation cycles, and of fungus α-amylase and W. anomalus HN006 supplementation on the biochemical parameters of lily rice wine were evaluated. The optimum quality of the wine, in terms of ethanol and residual sugar content, acidity levels and aroma, was obtained with 5% (w/v) solid residue addition, and supplementation with 10 U/g fungal α-amylase and 2% (v/v) W. anomalus inoculum on the 4th day of fermentation. Volatile compound profiles, the total amount of amino acids and the sensory characteristics of the lily rice wines produced by the two fermentation processes were also evaluated and compared. The lily rice wine obtained from our optimized experimental technology produced higher amounts of some esters, free fatty acids, alcohols, aldehydes, ketones, alkenes, volatile phenol and thiazole, in addition to higher total amino acid content and sensory scores compared to the traditionally brewed wine. Our process resulted in an intensification and improvement of lily rice wine aroma.

Corrigendum: Investigating the Effect of Selected Non-Saccharomyces Species on Wine Ecosystem Function and Major Volatiles.

[This corrects the article DOI: 10.3389/fbioe.2018.00169.].

On the evaluation of different saccharification schemes for enhanced bioethanol production from potato peels waste via a newly isolated yeast strain of Wickerhamomyces anomalus

The present study focuses on the exploration of the potential use of potato peels waste (PPW) as feedstock for bioethanol production, using a newly isolated yeast strain, Wickerhamomyces anomalus, via different saccharification and fermentation schemes. The saccharification of PPW was performed via thermal and chemical (acid, alkali) pretreatment, as well as via enzymatic hydrolysis through the use of commercial enzymes (cellulase and amylase) or enzymes produced at lab scale (alpha-amylase from Bacillus sp. Gb67), either separately or in mixtures. The results indicated that the enzymatic treatment by commercial enzymes led to a higher saccharification efficiency (72.38%) and ethanol yield (0.49 g/gconsumed sugars) corresponding to 96% of the maximum theoretical. In addition, acid pretreatment was found to be beneficial for the process, leading also to high hydrolysis and ethanol yields, indicating that PPW is a very promising feedstock for bio-ethanol production by W. anomalus under different process schemes.

Enhanced production of ethyl acetate using co-culture of Wickerhamomyces anomalus and Saccharomyces cerevisiae

The style and quality of Baijiu is greatly influenced by ethyl acetate. Therefore, improving and controlling the ethyl acetate levels in Baijiu is important. This study investigated ethyl acetate production using a co-culture of Saccharomyces cerevisiae Y3401 and Wickerhamomyces anomalus Y3604. More ethyl acetate was produced in mixed fermentations using both yeasts than in single fermentations. The highest ethyl acetate yield was 6.41g/L using a Y3401/Y3604 ratio of 3:1. Synergistic fermentation using both yeasts not only improved ethyl acetate production, but also increased the contents of other flavor compounds, such as β-phenethyl alcohol and phenethyl acetate. Therefore, the co-culture of S.cerevisiae and W.anomalus had a positive effect on ethyl acetate production and provides opportunities for altering the aroma and flavor perception of Baijiu.

Performance of non-Saccharomyces yeasts isolated from Jiaozi in dough fermentation and steamed bread making

The characteristics of three non-Saccharomyces yeasts, namely, Wickerhamomyces anomalus Y13, Saccharomycopsis fibuligera Y18, and Torulaspora delbrueckii Y22, isolated from Jiaozi in dough fermentation and steamed bread making were investigated and compared with those of Saccharomyces cerevisiae Y10. The maltose levels in the dough fermented by Y13, Y18, and Y22 in the entire fermentation were higher than those in the dough fermented by Y10. The CO2 production kinetics of Y22 was similar to that of Y10, but the total CO2 volume was slightly less. The volume of CO2 produced by Y13 and Y18 was less than 30% of that generated by Y10. The sensory qualities of Y22-prepared steamed bread were similar to those of Y10 and could also be accepted. The degree of whiteness of the steamed bread prepared with Y22 was higher than that produced with Y10. Steamed bread produced with each of the non-Saccharomyces yeasts contained unique volatile compounds, and the highest number of categories of volatile compounds were observed in the product prepared with Y22. The results indicated that non-Saccharomyces yeasts exhibited distinctive characteristics of dough fermentation and showed the potential for applications in dough fermentation and steamed bread making.

Evaluation of potentially probiotic attributes of certain dairy yeast isolated from buffalo sweetened Karish cheese

Egyptian traditional cheese has a long history and still represent an important part of the Egyptian diet. A lot of scientific studies in probiotic topic is usually related to bacteria, in particular lactic acid bacteria, and there is lack of information about potentially probiotic yeasts, except Saccharomyces boulardii. In the current study, 50 samples of traditional Egyptian buffalo sweetened cheese randomly were collected from five local Egyptian markets for yeast isolation. Isolated yeast species were identified using API20 kits techniques and the most frequently isolates were genotypically confirmed identified using the variability in the ITS rDNA. Appropriate in vitro assays have been conducted to examine their probiotic potentiality counting acid and bile salts tolerance, stimulated gastrointestinal tract tolerance, cell adhesion/hydrophobic characteristics, killer toxin productivity and antimicrobial activity against some clinical and food borne pathogens. The incidence of the obtained yeast taxa was found to be; S. cerevisiae (25%), Wickerhamomyces anomalus (23%), Pichia kudriavzevii (19%), Kluyveromyces lactis (17%), Geotrichum candidum (6%), Debaryomyces hansenii (4%), Candida tropicalis (3%), Cryptococcus neoformans (1%), Rhodotorula glabrata (1%) and Trichosporon cutaneum (1%). The most frequently isolates (S. cerevisiae, W. anomalus and P. kudriavzevii) exhibited high tolerance to bile salts elevated concentrations up to 2.0 %. W. anomalus could withstand the elevated bile salts concentrations and it was the most tolerable yeast isolate to intestinal juice environment. W. anomalus showed the lowest eradication from intestinal mucosa as indicated by the hydrophobicity average percentage 11.891% to xylene comparing to the P. kudriavzevii which showed the highest hydrophobicity average percentage of 46.185% to chloroform. Yeast isolates S. cerevisiae, W. anomalus and P. kudriavzevii (particularly W. anomalus) were recognized as ideal potentially probiotic model having in vitro properties that make them favorable candidates for probiotic applications.

Three dimensional structure prediction of panomycocin, a novel Exo-β-1,3-glucanase isolated from Wickerhamomyces anomalus NCYC 434 and the computational site-directed mutagenesis studies to enhance its thermal stability for therapeutic applications

Panomycocin is a naturally produced potent antimycotic/antifungal protein secreted by the yeast Wickerhamomyces anomalus NCYC 434 with an exo-β-1,3-glucanase activity. In this study the three dimensional structure of panomycocin was predicted and the computational site-directed mutagenesis was performed to enhance its thermal stability in liquid formulations over the body temperature for topical therapeutic applications. Homology modeling was performed with MODELLER and I-TASSER. Among the generated models, the model with the lowest energy and DOPE score was selected for further loop modeling. The loop model was optimized and the reliability of the model was confirmed with ERRAT, Verify 3D and Ramachandran plot values. Enhancement of the thermal stability of the model was done using contemporary servers and programs such as SPDBViewer, CNA, I-Mutant2.0, Eris, AUTO-MUTE and MUpro. In the region outside the binding site of the model Leu52 Arg, Phe223Arg and Gly254Arg were found to be the best thermostabilizing mutations with 6.26 K, 6.26 K and 8.27 K increases, respectively. In the binding site Glu186Arg was found to be the best thermostabilizer mutation with a 9.58 K temperature increase. The results obtained in this study led us to design a mutant panomycocin that can be used as a novel antimycotic/antifungal drug in a liquid formulation for topical applications over the normal body temperature.

Identifying yeasts using surface enhanced Raman spectroscopy.

The molecular fingerprints of yeasts Saccharomyces cerevisiae, Dekkera bruxellensis, and Wickerhamomyces anomalus (former name Pichia anomala) have been examined using surface-enhanced Raman spectroscopy (SERS) and helium ion microscopy (HIM). The SERS spectra obtained from cell cultures (lysate and non-treated cells) distinguish between these very closely related fungal species. Highly SERS active silver nano-particles suitable for detecting complex biomolecules were fabricated using a simple synthesis route. The yeast samples mixed with aggregated Ag nanoparticles yielded highly enhanced and reproducible Raman signal owing to the high density of the hot spots at the junctions of two or more Ag nanoparticles and enabled to differentiate the three species based on their unique features (spectral fingerprint). We also collected SERS spectra of the three yeast species in beer medium to demonstrate the potential of the method for industrial application. These findings demonstrate the great potential of SERS for detection and identification of fungi species based on the biochemical compositions, even in a chemically complex sample.

Role of biocontrol yeasts Debaryomyces hansenii and Wickerhamomyces anomalus in plants' defence mechanisms against Monilinia fructicola in apple fruits

The role of killer yeasts of the species Debaryomyces hansenii and Wickerhamomyces anomalus in biocontrol of Monilinia fructicola, and their involvement in plant defence mechanisms against brown rot in apple fruits, were investigated. D. hansenii KI2a and W. anomalus BS91 strains showed the highest in vitro biocontrol activity, inhibiting mycelium growth by 69.53% and 66.08% respectively, as compared to control fungal cultures. Brown rot on apple fruits was significantly reduced by BS91 and two strains of D. hansenii KI2a and AII4b by 92.46%, 85.10% and 70.02%, respectively, in comparison to infected fruits, which did not receive any pre-treatment. In enzymatic tests, the most significant changes in peroxidase (POD) and catalase (CAT) activities were observed in fruits inoculated either with BS91 followed by M. fructicola infection or with AII4b yeast strain alone, where POD activities were significantly higher by 67% and 54%, respectively, and CAT activities were significantly lower by 65% and 68%, respectively, than in untreated control fruits. These results confirmed the ability of killer yeasts to influence host-defence related enzyme activities in apple fruit tissue and may suggest that AII4b killer strain has a potential as biocontrol agent prior to infection by triggering immune response mechanisms in plant tissue, whereas BS91 strain is the most effective during pathogen infection and could be used as biocontrol agent in postharvest disease onset. Accordingly, the antagonistic strains of W. anomalus BS91 and D. hansenii KI2a and AII4b could be proposed as active ingredients for the development of biofungicide against M. fructicola.

Yeasts and bacteria associated with pineapple fruit during postharvest handling

Fungi are common microorganisms causing peduncle moulds in pineapple fruits, but there is a lack of information about other microorganisms colonizing pineapples. Yeasts and bacteria are among the main microorganisms recovered from different fruits, but there is not enough information about their role in pineapple fruit. The objective of this research was to determine and quantify the frequency and populations of yeasts and bacteria associated with 'MD-2' (“Gold Extra Sweet”) pineapple fruits in postharvest. Twelve monthly samplings were performed in two packing houses in Costa Rica. The colony forming units (CFU log10) of yeasts and bacteria (Y+B) were determined in fruit peel and peduncle, before (WP) and after commercial processing (P), and in both WP and P fruits stored 19 days at 7°C + 3 days at 18°C. Molecular characterization analysing ITS1 and ITS2 regions and frequency of the main recovered yeast was carried out. Populations of Y+B were greater in WP than in P fruits throughout the year in both packing houses, with values between 0.5 and 4.6 CFU mL(-1) in WP peduncles, and between 0 and 2.7 CFU mL(-1) in P peduncles. In peels, populations were similar between P and WP fruits with values between 0.7 and 5.6 CFU mL(-1). At the end of storage, populations of Y+B reached a maximum of 6.8 CFU mL(-1) in WP peduncles and of 5.8 CFU mL(-1) in P peels. Wickerhamomyces anomalus was the most frequent yeast isolated with a range of 20-100%, and it has been reported as a potential biocontrol microorganism in different crops. More research is needed to identify the role of yeasts and bacteria in pineapple fruits, especially the potential of W. anomalus as a biocontrol agent that could be introduced as part of an integrated program for management of pineapple peduncle moulds.

Dense tracking of the dynamics of the microbial community and chemicals constituents in spontaneous wheat sourdough during two months of backslopping

Wheat sourdough is a common traditional fermented food that is produced worldwide. However, product quality of spontaneous sourdough is not easy to control because it depends on natural fermentation and backslopping, about which little is known, notably after ten backslopping steps. To this end, we tracked the spontaneous fermentation of three sourdoughs made from wheat flours during 32 backslopping steps for 60 days. At 24 time points, the microbial community was analyzed by both culture-dependent and culture-independent methods and its chemical constituents were assessed. Dynamic changes were observed in the microbial community, which showed a common succession pattern among the three sourdoughs at the bacterial family level and differences at the species level. The bacterial communities evolved through three phases that were driven by different groups of lactic acid bacteria (LAB) species. The dynamism among the metabolites also differed, depending on the species composition of the LAB and yeast communities. In one sourdough, the growth of Saccharomyces cerevisiae was detected along with a concentration of increased ethanol, while in the other two sourdoughs, Wickerhamomyces anomalus was detected without ethanol production. Regarding the LAB communities, two sourdoughs were eventually co-dominated by Lactobacillus plantarum and L. brevis, while the other sourdough was eventually dominated solely by the heterolactic fermentative bacterium Lactobacillus fermentum, and ethanol was produced at the same level as lactic acid. Further research is needed to determine the bacterial and yeast species involved in the fermentation of sourdough, to help improve the design and quality control of the final product.

Corrigendum: Unequivocal identification of an underestimated opportunistic yeast species, Cyberlindnera fabianii, and its close relatives using a dual-function PCR and literature review of published cases.

Although Cyberlindnera fabinaii is a rare opportunist yeast species, its ability to cause septicemia, produce biofilm, and rapid acquisition of resistance to fluconazole and voriconazole, reinforced the urge for its identification from its closely related species. Widely used biochemical assays mainly identify Cyberlindnera fabinaii as Cyberlindnera jadinii and Wickerhamomyces anomalus, resulting in underestimation of this yeast in clinical settings. Moreover, the urge for a reliable molecular means of identification remains unsolved for 28 years. In order to unequivocally differentiate Cy. fabianii, Cy. mississipiensis, Cy. jadinii, and W. anomalus, we designed a dual-function multiplex polymerase chain reaction (PCR) assay. Challenging our dual-function multiplex PCR assay with 30 most clinically important yeast species, proved its specificity. Although conventional PCR could differentiate four target species, the real-time PCR counterpart due to Tm overlap misidentified Cy. mississipiensis as Cy. jadinii. Alongside of presenting a comprehensive literature review of published cases of Cy. fabianii from 1990 to 2018, we collected various clinical isolates from Tehran, Shiraz, and Fasa (July 1, 2017, to December 31, 2017) to find a passive relative distribution of these closely-related species in Iran. Subjecting our Iranian collection of yeast isolates to matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS and LSU and ITS rDNA sequencng revealed six isolates of Cy. fabianii (central venous catheter n = 2 and vaginal swabs n = 4) and one isolate of Cy. jadinii (vaginal swabs). Due to the use of biochemical assays in global ARTEMIS study, we encourage reidentification of clinical isolates of Cy. jadinii and Cy. jadinii using MALDI-TOF or Sanger sequencing that might lead to correcting the distribution of this fungus.

Screening and identification of an antagonistic yeast controlling postharvest blue mold decay of pears and the possible mechanisms involved

Postharvest disease of pears caused by pathogens results in great economic losses. The aim of this research was to isolate a strain of potential antagonistic yeast from soil of orchards, and to test the control efficacy against postharvest blue mold decay of pears. By molecular biological identification based on comparative sequence analysis of 5.8S rDNA gene, the antagonistic strain was identified as Wickerhamomyces anomalus. The results showed that W. anomalus significantly reduced the disease incidence and lesion diameter of blue mold of pears compared with the control in vivo. The disease incidence caused by Penicillium expansum of pears was only 5.56%, when treated with 1 × 108 cells/mL W. anomalus, compared with 100% disease incidence of the control. In vitro test showed that W. anomalus reduced the spore germination rate and germ tube length of P. expansum. Meanwhile, polyphenoloxidase (PPO), peroxidase (POD), catalase (CAT) and chitinase (CHI) activities of the pears treated by W. anomalus were significantly higher than that of the control. And the expression levels of defense-related enzymes were significantly induced by W. anomalus. All these results indicated that W. anomalus has the potential to control postharvest diseases of pears, and the mechanisms involved in inhibiting spore germination and germ tube length, induction of the activities of the defense-related enzymes of pears, and improvement of the expression levels of defense-related genes of pears.

MALDI-TOF/TOF mass spectrometry for determination of yeast diversity in traditional cornelian cherry tarhana produced with different cereal/pseudocereal flours

This study is to determine the dynamics in the microflora of cornelian cherry tarhana (CCT), a traditional food of Turkey, by MALDI-TOF/TOF MS. Non-fermented and fermented CCT productions were performed by using flours of bread wheat, wholegrain hull-less barley, buckwheat, and clear flour. Identification of the isolates obtained from raw materials and various production steps of the CCT was performed by MALDI-TOF/TOF MS. Dendograms were prepared by cluster analysis and the distances between the strains isolated during production stages and from cornelian cherry puree were determined. Totally, 231 isolates were obtained and 45.5% of them were identified at species level, 30.3% at genus level while 24.2% of the isolates could not be identified. It was found that microflora of cornelian cherry tarhana is mainly composed of yeasts. Thirty-two percent of the identified yeast isolates were Hanseniaspora uvarum and the others were Saccharomycescerevisiae (19.6%), Torulaspora delbrueckii (18.6%), Candida krusei (11.3%), Candida lusitaniae (9.3%), Metschnikowia pulcherrima (3.1%), Wickerhamomyces anomalus (2.1%), Candida kefyr (2.1%), Cyberlindnera fabianii (1%), and Candida parapsilosis (1%). Only two lactic acid bacteria could be isolated, which were Lactobacillus reuteri and Enterococcus spp., originating from buckwheat flour and clear flour, respectively. Dendograms revealed that some of the yeast strains isolated during production were originating from cornelian cherry. Microflora of CCT was investigated for the first time. This is one of the few studies using MALDI-TOF/TOF MS for identification of food originated yeasts. Novel species–identified, endogenic yeasts which could have potential technological characteristics were introduced.

Yeast dynamics and changes in volatile compounds during the fermentation of the traditional Chinese strong-flavor Daqu

Daqu is the major source of microorganisms, enzymes, flavour compounds, and their precursors in the Chinese liquor production process. In the present study, the yeast community and the volatile compounds of Chinese strong-flavor Daqu during its fermentation were investigated using PCR-DGGE and HS-SPME/GC–MS, respectively. The results indicated that the band number, dominance, diversity and similarity of the 26S rDNA were clearly distinct in the DGGE patterns, due to the significant diversity expressed by the disparate yeast communities in different phases. More than 14 yeast genera, such as Saccharomycopsis fibuligera, Hanseniaspora uvarum, Geotrichum bryndzae, Wickerhamomyces anomalus, Yarrowia lipolytica, Candida mucifera, Issatchenkia orientalis, Alternaria tenuissima, Kazachstania barnettii, Candida intermedia, Kazachstania barnettii, Pichia occidentalis, Saccharomyces cerevisiae, Pichia kudriavzevii and Saturnispora silvae were observed in the fermentation, among which the dominant strains were Pichia kudriavzevii and Saturnispora silvae. Furthermore, 43 volatile compounds, including 15 esters, 10 acids, 8 alcohols, 4 aldehydes, 2 alkenes, 1 ketone, 1 phenol, 1 furan and 1 pyrrole, were identified. The trajectory plots of the compounds acquired during consecutive stages of incubation revealed that different samples of Daqu correlated with specific groups of volatile compounds. These findings would help to understand the fermentation mechanism of Daqu production.

Isavuconazole MIC distribution of 29 yeast species responsible for invasive infections (2015–2017)

ObjectivesIsavuconazole is a recent extended-spectrum triazole with activity against yeasts. However, few data are available about the in vitro activity of rare yeast species. We report the MIC distribution of isavuconazole compared with fluconazole for a large collection of common or rare yeasts. MethodsIsavuconazole and fluconazole MICs were determined using the EUCAST method for 1457 clinical isolates, mainly recovered from invasive infections, belonging to 29 species. They were sent to the National Reference Centre for Invasive Mycoses & Antifungals between January 2015 and October 2017 and species identification was performed using a polyphasic approach (matrix-assisted laser desorption/ionization time of flight analysis and a molecular method). ResultsIsavuconazole had effective in vitro activity against Cryptococcus neoformans (MIC90 < 0.25 mg/L), the five most common Candida spp. (MIC90 ≤ 0.5 mg/L for Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis, and Candida krusei) and also against the majority of rare species, including Candida kefyr and Candida lusitaniae. A few isolates of C. albicans (0.7%, 3/404), C. glabrata (2.7%, 5/184), C. tropicalis (1.0%, 1/96) and C. parapsilosis (0.8%, 1/127) exhibited MIC ≥4 mg/L. All were also resistant to fluconazole according to the EUCAST breakpoints. Some isolates with isavuconazole MIC ≥4 mg/L were also observed among rarer species: Meyerozyma guilliermondii (8.7%, 2/23), Wickerhamomyces anomalus (10.0%, 1/10). Other rare species Saprochaete clavata, Magnusiomyces capitatus, and Rhodotorula mucilaginosa had high MIC50 (≥1 mg/L) and MIC90 (≥4 mg/L) and could be considered as resistant to isavuconazole. ConclusionsWe confirmed the good in vitro activity of isavuconazole against common Candida, Cryptococcus species and the majority of the rare yeast species studied.