Identification Of Yeasts Research Articles

In Search for Reasons behind Helicobacter pylori Eradication Failure-Assessment of the Antibiotics Resistance Rate and Co-Existence of Helicobacter pylori with Candida Species.

Helicobacter pylori eradication is characterized by decreasing successful eradication rates. Although treatment failure is primarily associated with resistance to antibiotics, other unknown factors may influence the eradication outcome. This study aimed to assess the presence of the antibiotics resistance genes in H. pylori and the presence of Candida spp., which are proposed to be endosymbiotic hosts of H. pylori, in gastric biopsies of H. pylori-positive patients while simultaneously assessing their relationship. The detection and identification of Candida yeasts and the detection of mutations specific for clarithromycin and fluoroquinolones were performed by using the real-time PCR (RT-PCR) method on DNA extracted from 110 gastric biopsy samples of H. pylori-positive participants. Resistance rate to clarithromycin and fluoroquinolone was 52% and 47%, respectively. Antibiotic resistance was associated with more eradication attempts (p < 0.05). Candida species were detected in nine (8.18%) patients. Candida presence was associated with older age (p < 0.05). A high rate of antibiotic resistance was observed, while Candida presence was scarce, suggesting that endosymbiosis between H. pylori and Candida may not be a major contributing factor to the eradication failure. However, the older age favored Candida gastric mucosa colonization, which could contribute to gastric pathologies and microbiome dysbiosis.

Influence of Native S. cerevisiae Strains on the Final Characteristics of “Pago” Garnacha Wines from East Spain

This work studies the variability of the Saccharomyces cerevisiae present during the spontaneous fermentation of Garnacha grapes’ musts from a “Pago” winery from the east of Spain. The parameters used to select yeast are those related to growth, fermentative behaviour, and the influence on the wine’s aroma and polyphenolic composition. Yeast identification was performed by ITS analysis and typed by Hinfl mDNA restriction profile analysis. Growth and metabolic characteristics of the isolates were determined by laboratory-scale fermentations of sterile Garnacha must, and the composition of the polyphenolic and the volatile compounds, and the sensory attributes of the small-scale produced red wines were determined. Ten S. cerevisiae strains were isolated and characterized. Overall, strain 22H quickly grew, produced wines with moderate ethanol concentrations and low volatile acidity, and obtained the highest colour and aroma scores, plus a high score for sensory attributes.

Identification of Pathogenic and Opportunistic Yeasts in Pigeon Excreta by MALDI-TOF Mass Spectrometry and Their Prevalence in Chon Buri Province, Thailand.

Pigeon excreta can cause environmental and public health issues, particularly in urban and public areas. They are reservoirs of several human pathogens including fungi, bacteria, and viruses. Epidemiological data of pathogenic and opportunistic yeasts in pigeon droppings in Chon Buri, one of the most reputable tourist cities of Thailand, are scarce. The present study aimed to identify yeasts in pigeon droppings by MALDI-TOF mass spectrometry, and to study their prevalence in Chon Buri, Thailand. A total of 200 pigeon fecal samples were collected randomly from all 11 districts of Chon Buri. A sum of 393 yeast-like colonies were isolated on Sabourand's dextrose agar and CHROMagar media. These isolates were further confirmed for their species by MALDI-TOF MS. Twenty-four yeast species belonging to 11 different genera were identified in pigeon fecal samples. Candida spp., predominantly C. krusei (14.32%), were the most prevalent yeast species. Other yeast species, including C. glabrata (12.73%), C. metapsilosis (11.93%), Lodderomyces elongisporus (10.87%), C. tropicalis (7.16%), C. albicans (5.83%), and Cryptococcus neoformans (4.77%) were identified. This study provides valuable epidemiological data and diversity of yeasts in pigeon droppings in Chon Buri, Thailand, and also supports the use of MALDI-TOF MS for yeast identification and epidemiological surveillance.

Lactiplantibacillus argentoratensis and Candida tropicalis Isolated from the Gastrointestinal Tract of Fish Exhibited Inhibitory Effects against Pathogenic Bacteria of Nile Tilapia

Nile tilapia is one of the most consumed farmed fish in the world. The outbreak of pathogenic bacterial diseases causes high mortality rates and economic losses in Nile tilapia farming. Antibiotic administrations are commonly utilized to inhibit and prevent bacterial infections. However, antibiotics are expensive and cause serious concerns for antibiotic resistance in fish that can be potentially transferred to humans. As an alternative solution, probiotics can be used to prevent infection of pathogenic bacteria in fish. In this work, both bacteria and yeast were isolated from fish gastrointestinal tracts and their inhibitory activity against Nile tilapia pathogenic bacteria was evaluated, as well as other probiotic properties. In this study, 66 bacteria and 176 acid tolerant yeasts were isolated from fish gastrointestinal tracts. Of all isolated microorganisms, 39 bacterial and 15 yeast isolates with inhibitory effect against pathogens were then examined for their probiotic properties (acidic and bile salt resistance, adhesion potential, and biofilm formation), formation of antibacterial factor survival rate under simulated gastrointestinal fluid, and safety evaluation. AT8/5 bacterial isolate demonstrated probiotic properties and the highest inhibition against all 54 tested pathogens while YON3/2 yeast isolate outperformed the inhibitory effect among all yeast isolates. These two probiotic isolates were further identified by 16S rDNA and the D1/D2 domain of 26S rDNA sequence analysis for bacterial and yeast identification, respectively. AT8/5 and YON3/2 showed the highest similarity to Lactiplantibacillus argentoratensis and Candida tropicalis, respectively. This is the first report on isolated L. argentoratensis and C. tropicalis with antipathogenic bacteria of Nile tilapia properties. Collectively, AT8/5 and YON3/2 could be potentially used as promising alternatives to existing antibiotic methods to prevent pathogenic bacteria infection in Nile tilapia farming.

Clinical evaluation of polymerase chain reaction coupled with quantum dot fluorescence analysis in the identification of bacteria and yeasts in patients with suspected bloodstream infections.

Bloodstream infections are serious and complex infectious diseases that often require a rapid diagnosis. Polymerase chain reaction coupled with quantum dot fluorescence analysis (PCR-QDFA) is a novel diagnostic technique. This study aimed to evaluate the diagnostic performance of PCR-QDFA for pathogen detection in patients with suspected bloodstream infections (BSIs). It evaluates 29 kinds of common pathogens (24 bacteria and 5 yeasts) from blood culture bottles. The results of PCR-QDFA identification and traditional microbial laboratory identification were compared, and the latter was used as the 'gold standard' to analyse the diagnostic performance of the PCR-QDFA. In total, 517 blood culture bottles were included in this study. The PCR-QDFA identified microorganisms in 368/422 (87.2%) samples with monomicrobial growth. For the pathogens on the PCR-QDFA list, the assay showed a higher sensitivity of 97.4% (368/378). When polymicrobial growth was analysed, the PCR-QDFA successfully detected 19/25 (76%) microorganisms on the PCR-QDFA list. In addition, 82/82 negative blood culture bottles also showed no pathogens by PCR-QDFA with a specificity of 100%. In conclusion, the PCR-QDFA assay could identify a majority of the common pathogens encountered in clinical practice, showing excellent diagnostic performance for pathogen detection in patients with suspected BSIs.

Candidiasis and Other Emerging Yeasts.

The review presents a comprehensive and updated information on the contemporary status of invasive candidiasis (IC), other emerging yeast infections, and the challenges they present in terms of at-risk population, specific virulence attributes, and antifungal susceptibility profile. With the advancement in medical field, there has been parallel expansion of vulnerable populations over the past two decades. This had led to the emergence of a variety of rare yeasts in healthcare settings, both Candida and non-Candida yeast causing sporadic cases and outbreaks. The advancements in diagnostic modalities have enabled accurate identification of rare Candida species and non-Candida yeast (NCY) of clinical importance. Their distribution and susceptibility profile vary across different geographical regions, thus necessitating surveillance of local epidemiology of these infections to improve patient outcomes. The challenges in management of IC have been complicated with emergence of newer species and resistance traits. C. tropicalis has already overtaken C. albicans in many Asian ICUs, while C. auris is rising rapidly worldwide. Recent genomic research has reclassified several yeasts into newer genera, and an updated version of MALDI-TOF MS or ITS sequencing is necessary for accurate identification. Having a knowledge of the differences in predisposing factors, epidemiology and susceptibility profile of already established pathogenic yeasts, as well as new emerging yeasts, are imperative for better patient management.

Molecular identification of yeasts from Turkish traditional cheeses: Extracellular enzyme activities and physiological properties important for dairy industry

Abstract. Gunay M, Genc TT. 2023. Molecular identification of yeasts from Turkish traditional cheeses: Extracellular enzyme activities and physiological properties important for dairy industry. Nusantara Bioscience 15: 1-11. The determination of yeast microbiota in cheeses and the physiological properties of yeasts are very important for the dairy industry. In addition, the physiological features, proteolytic and lipolytic activities, and stress tolerance of yeasts have a significant role in the selection of starter yeast species for cheese ripening. This study aimed to determine industrially important yeasts isolated from cheese samples. Molecular techniques identified the isolated yeast strains. The yeast strains’ extracellular enzyme activities, fermentation capacities, and thermotolerance and osmotolerance properties were also evaluated. A total of 81 yeast strains were isolated and characterized from three types of cheese samples. PCR-RFLP determined the isolated yeast strains and sequence analysis of ITS1-5.8S-ITS2 and 26S rDNA regions. A maximum parsimony tree was constructed by MEGA X software to evaluate the phylogenetic relationship of identified yeast strains. Candida intermedia, Candida parapsilosis, Clavispora lusitaniae, Debaryomyces hansenii, Kluyveromyces marxianus, Pichia kudriavzevii, and Wickerhamomyces anomalus yeast species were identified on cheese samples. The distribution of identified yeast species on cheese samples was determined as 48.1% for W. anomalus, 17.3% for K. marxianus, 14.8% for C. parapsilosis, 8.6% for D. hansenii, 4.9% for Cl. lusitaniae, 3.7% for C. intermedia and 2.5% for P. kudriavzevii. The W. anomalus yeast species was common in three cheese types. All strains of W. anomalus and P. kudriavzevii yeast species, three C. parapsilosis, and two Cl. lusitaniae yeast strains have important physiological properties for industrial applications. These yeast strains have the potential to be used in combination as starter cultures to improve cheese maturation in the future. This comprehensive study identifies yeast species by ITS1-5.8S-ITS2 and 26S rDNA regions and determines industrially important yeast species using multiple criteria (extracellular enzyme activity, stress tolerance, and fermentation capacity).

Diversity Analysis of Culturable Epiphytic Microbial Consortia of Table Grape Berry Surface

ABSTRACT The health and yield of grapes are affected by the microorganisms associated with the grapevine. The diversity of microorganisms present on the wine grape varieties is well defined whereas, the information associated with the microorganisms of table grape varieties remains scarce. In the present study, culture-dependent method was used to isolate the microbes present on the surface of the commercial white seedless table grape cultivar, Thompson Seedless at different stages of berry development. The microbial load of the grape berry surface increased as the berry progressed toward the ripening stage resulting in the identification of core bacteria (29), filamentous fungi (19) and yeast (3). A diversity analysis study also revealed that Cladosporium cladosporioides, was found in the vineyard on grapes from the early berry development stages, as an emerging pre-harvest pathogen. The study would help in understanding and exploiting the microbiota of table grape berry in agronomic and biotechnological applications.

Production, Purification and Characterization of Terpenes Isolated From Two New Strains of Yeasts in Iraq and Study of Their Antiparasitic Activity

The current study was included isolation and identification of yeasts from five sediments soil samples from Al-Faw and Shatt al-Arab in Basrah provinces, Iraq. The soil samples were collected during fallow period 1-1-2021 to 1-6-2022. In the primary isolation dilution method used for cultured soil samples, two-crud colonies filtration was used. Two types of terpenes (T1, T2) were purified from culture filtrates of both species Cystobasidium benthicum and C .minutum separately. The thin layer chromatography and column chromatography were used in the first step of purification. Cytotoxicity test revealed no toxic effect for both terpenes at 0.2 gm / ml concentration. The two terpenes were identified using ultra violet and infra-red spectroscopy as well. Therefore, the results showed the terpenes nature of both toxins and determination of important active groups in the structure of the two isolated terpenes. The current study aimed to search for more treatments that limit the vitality of the larval stages of the parasite, so it was done antiparasite activity for both terpenes were performed against Echinococcus granulosus the results showed the T1 more activity against parasite compared with T2.

Diversity of duckweed (&lt;i&gt;Lemnaceae&lt;/i&gt;) associated yeasts and their plant growth promoting characteristics

&lt;abstract&gt; &lt;p&gt;The diversity of duckweed (&lt;italic&gt;Lemnaceae&lt;/italic&gt;) associated yeasts was studied using a culture-dependent method. A total of 252 yeast strains were isolated from 53 duckweed samples out of the 72 samples collected from 16 provinces in Thailand. Yeast identification was conducted based on the D1/D2 region of the large subunit (LSU) rRNA gene sequence analysis. It revealed that 55.2% and 44.8% yeast species were Ascomycota and Basidiomycota duckweed associated yeasts, respectively. Among all, &lt;italic&gt;Papiliotrema laurentii&lt;/italic&gt;, a basidiomycetous yeast, was found as the most prevalent species showing a relative of frequency and frequency of occurrence of 21.8% and 25%, respectively. In this study, high diversity index values were shown, indicated by the Shannon-Wiener index (&lt;italic&gt;H′&lt;/italic&gt;), Shannon equitability index (&lt;italic&gt;E&lt;sub&gt;H&lt;/sub&gt;&lt;/italic&gt;) and Simpson diversity index (&lt;italic&gt;1-D&lt;/italic&gt;) values of 3.48, 0.86 and 0.96, respectively. The present results revealed that the yeast community on duckweed had increased species diversity, with evenness among species. Principal coordinate analysis (PCoA) revealed no marked differences in yeast communities among duckweed genera. The species accumulation curve showed that the observed species richness was lower than expected. Investigation of the plant growth promoting traits of the isolated yeast on duckweed revealed that 178 yeast strains produced indole-3-acetic acid (IAA) at levels ranging from 0.08–688.93 mg/L. Moreover, siderophore production and phosphate solubilization were also studied. One hundred and seventy-three yeast strains produced siderophores and exhibited siderophores that showed 0.94–2.55 activity units (AU). One hundred six yeast strains showed phosphate solubilization activity, expressed as solubilization efficiency (SE) units, in the range of 0.32–2.13 SE. This work indicates that duckweed associated yeast is a potential microbial resource that can be used for plant growth promotion.&lt;/p&gt; &lt;/abstract&gt;

A Comprehensive Review of Identification Methods for Pathogenic Yeasts: Challenges and Approaches.

Given the increasing incidence of yeast infections and the presence of drug-resistant isolates, accurate identification of the pathogenic yeasts is essential for the management of yeast infections. In this review, we tried to introduce the routine and novel techniques applied for yeast identification. Laboratory identification methods of pathogenic yeast are classified into three categories; I. conventional methods, including microscopical and culture-base methods II. biochemical/physiological-processes methods III. molecular methods. While conventional and biochemical methods require more precautions and are not specific in some cases, molecular diagnostic methods are the optimum tools for diagnosing pathogenic yeasts in a short time with high accuracy and specificity, and having various methods that cover different purposes, and affordable costs for researchers. Nucleotide sequencing is a reference or gold standard for identifying pathogenic yeasts. Since it is an expensive method, it is not widely used in developing countries. However, novel identification techniques are constantly updated, and we recommend further studies in this field. The results of this study will guide researchers in finding more accurate diagnostic method(s) for their studies in a short period of time.

Isolation and identification of filamentous fungi and yeasts with zoonotic potential obtained from cattle egret (Bubulcus ibis) droppings.

The different microorganisms that make up the normal microbiota of birds can be present in different substrates such as the soil and other elements that make up the habitat. In the case of the cattle egret, the intestinal microbiota can change due to partially migratory habits. Thus, this study aimed to isolate and identified fungi and yeasts with zoonotic potential obtained from cattle egret (Bubulcus ibis) droppings settler in Tulancingo, Hidalgo, at Eastern economic zone of Mexico. Cattle egret droppings were collected for analysis, a total of 240 pool samples, which were spread on Sabouraud agar and incubated at 25.00 - 37.00 ˚C for 2 to 3 days. Filamentous fungi and yeast were identified by morphology and Lactophenol Blue staining or Chinese Ink stains. Filamentous fungi genera Mucor spp. (42.35%), Rhizopus spp. (26.71%); Penicillium spp. (13.35%); Paecilomyces spp. (11.40%); Scedosporium spp. (1.95%); and, from yeasts such as Cryptococcus spp. (2.29%); Rhodotorula spp. (1.95%) were identified. In this work, the presence of filamentous fungi genera and yeasts with zoonotic potential were isolated from droppings of cattle egret. The clinical presentation of fungal infections in humans can occur when immunosuppression is present or different predisposition factors are conjugated. The presence of birds and their dropping in anthropogenic activities is not a predisposing factor for the presentation of the disease in immunologically competent humans.

Molecular identification of LAB and yeasts from traditional sourdoughs and their impacts on the sourdough bread quality characteristics

In this research, the LAB and yeast isolations and identifications of homemade traditional sourdoughs were investigated. Both LAB and yeasts were identified by the PCR method and used in the production of sourdough bread (SDB). Twelve types of SDB were produced from combinations of isolated LAB and yeasts. Eleven LAB and yests were identified from 36 sourdoughs. The most frequently isolated LAB species were Lactobacillus brevis (45.0%), Pediococcus acidilactici (20.0%) and Lactobacillus plantarum (18.3%) while other LAB species were isolated by only 1.7–3.5%. On the other hand, 27.5% of the isolates were Saccharomyces cerevisiae, which was followed by Pichia kudriavzevii (25.0%) and Kluyveromyces marxianus (12.5%). The total titratable acidity and pH of the sourdough ranged from 3.10 to 34.45% and from 4.05 to 4.80 respectively. High acceptable loaf height (7.2 cm), moisture (30.05%), dry matter (69.95%), volume (1370 cm3), specific volume (4.35 cm3 g−1) and sensory value (62 scores) were determined for SDB12. Isolated LAB is mainly composed of heterofermentative species (75%). Among the bread produced with the combination of LAB and yeasts, the SDB12 was the most preferred SDB in terms of sensory analysis and other quality characteristics. The use of homofermentative and heterofermentative LAB and yeast combinations provided high-quality SDB. This would be due to the symbiotic growth of these microorganisms. The use of L. plantarum by L. brevis and by other species resulted in high-quality SDB.

MALDI-TOF MS Identification of some Clinically-Relevant Filamentous Fungi with the Direct Smear Method, a Simple Sample Preparation Method.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a powerful technique for the identification of microorganisms. The technique normally requires a sample preparation procedure before instrumental analysis, which can be somewhat labor-intensive when numbers of samples are large. The direct smear method, in which samples are directly smeared on the sample plates and subsequently subjected to instrumental analyses, can save time and is less labor-intensive. However, the method has rarely been tested on filamentous fungi, although it has been successfully used in the identification of bacteria and yeasts. In the present study, we examined the method using clinically-collected filamentous fungi. Three hundred forty-eight isolates of filamentous fungi representing 9 species collected from body fluids of patients were analyzed on the VITEK MS version 3.0 system, a popular commercial MALDI-TOF MS system, using the direct smear method. For those misidentified or unidentified, the samples were retested. All fungal species were determined through DNA sequencing. Among 334 isolates that were included in the database of the VITEK system, 286 (85.6%) samples were correctly identified. After retesting, the rate of correct identification increased to 91.0%. Aspergillus fumigatus exhibited a 95.2% rate of correct identification before retesting, whereas Aspergillus niger showed the rate at only 46.5% (58.1% even with retesting). The direct smear method could be used in the identification of filamentous fungi found in body fluids of patients by MALDI-TOF MS at good rates of correct identification. The method is simple and time-saving, and deserves further evaluation.

Isolation and identification of killer yeasts from Psidium gujava

Isolation and identification of killer yeasts from Psidium gujava

Phenotypic Characterization of Candida species in Tertiary Care Hospital of Eastern Nepal

Background: Candida albicans is one of the most frequently isolated yeast in clinical laboratories and studies have shown that it accounts for up to 80% of the yeast recovered from the site of infection. Candida species have emerged as significant opportunistic fungal pathogens and the conventional methods of yeast identification are reported to be cumbersome with delayed diagnosis and initiation of treatment. Thus rapid identification and speciation of Candida species is essential in clinical laboratories.&#x0D; Materials and Methods: A hospital based cross sectional study was carried out in the department of microbiology, Nobel medical college from January 2020 to December 2020. Approval was acquired from the Institutional Review Committee. Various clinical specimens were obtained and identification as per the standard microbiological procedures. Data were analyzed by SPSS, version 20.&#x0D; Results: A total of 62 Candida species were isolated out of which 65% were from male and 35% were from female patients. Candida albicans was found to be the most common species with 68%. The highest incidence was seen in the age group below 20 years and 21 – 40 years with 32.25% cases each followed by 41-60 years with 20.96% cases. Among 62 specimens, urine samples yielded the highest number of Candida species 48.38% followed by sputum samples with 29.03% Candida species. High vaginal swab (HVS) yielded 12.9% Candida species and blood samples yielded 9.67% Candida species.&#x0D; Conclusion: Candida albicans is still the most significant clinically but other non albicans are also emerging significant pathogens and warrant routine discrimination in clinical laboratories.

Antifungal susceptibility profiles and drug resistance mechanisms of clinical Candida duobushaemulonii isolates from China.

Candida duobushaemulonii, type II Candida haemulonii complex, is closely related to Candida auris and capable of causing invasive and non-invasive infections in humans. Eleven strains of C. duobushaemulonii were collected from China Hospital Invasive Fungal Surveillance Net (CHIF-NET) and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF), VITEK 2 Yeast Identification Card (YST), and internal transcribed spacer (ITS) sequencing. Whole genome sequencing of C. duobushaemulonii was done to determine their genotypes. Furthermore, C. duobushaemulonii strains were tested by Sensititre YeastOne™ and Clinical and Laboratory Institute (CLSI) broth microdilution panel for antifungal susceptibility. Three C. duobushaemulonii could not be identified by VITEK 2. All 11 isolates had high minimum inhibitory concentrations (MICs) to amphotericin B more than 2 μg/ml. One isolate showed a high MIC value of ≥64 μg/ml to 5-flucytosine. All isolates were wild type (WT) for triazoles and echinocandins. FUR1 variation may result in C. duobushaemulonii with high MIC to 5-flucytosine. Candida duobushaemulonii mainly infects patients with weakened immunity, and the amphotericin B resistance of these isolates might represent a challenge to clinical treatment.

Development of a novel SRAP-SCAR marker for rapid identification of lager and ale types in brewer's yeast.

Beer is a globally consumed and universally popular beverage. According to the fermentation conditions of brewer's yeast, ale yeast and lager yeast are the two major varieties. Normal phenotypic and genotypic approaches are insufficient and time-consuming for identifying these two forms of yeast. Therefore, a method for the rapid and cost-effective identification of lager and ale-type brewer's yeasts is necessary. In this study, we analysed the genetic diversity of 23 industrial brewer's yeasts from around the world using sequence-related amplified polymorphism (SRAP) markers and produced stable sequence characteristic amplification region (SCAR) markers. The specific DNA fragments identified by the SRAP marker were sequenced and primers were constructed; the resultant SCAR marker (757bp) was then confirmed against the indicated brewer's yeast type. The development of SRAP-SCAR marker is more economical, simple, and fast compared to morphological markers.

Characterization of kefir yeasts with antifungal capacity against Aspergillus species.

Kefir is a fermented probiotic drink obtained by placing kefir granules in a suitable substrate. The kefir granules are a consortium of bacteria and yeasts embedded in a exopolysaccharide matrix. The aim of this research was the isolation and identification of yeasts from kefir of different origin, the evaluation of their antifungal capacity against Aspergillus spp., and the characterization of virulence related traits. Using RFLP of ITS1/ITS4 region, D1/D2 region sequencing, and RAPD techniques, 20 kefir isolates were identified as Geotrichum candidum, Pichia kudriavzevii, Pichia membranifaciens, Saccharomyces cerevisiae, and Candida ethanolica. Their antifungal capacity was evaluated by their conidia germination reduction, which allowed the selection of eight isolates with high to moderate conidia germination reduction against Aspergillus flavus and Aspergillus parasiticus. Furthermore, these selected isolates showed growth inhibition on contact in the dual culture assay for both Aspergillus species and 3 of them-belonging to S. cerevisiae and P. kudriavzevii species-generated volatile organic compounds which significantly affected the growth of both fungi. For the evaluation of virulence-related traits, growth at high temperatures, enzymatic activities, and the adhesion to Caco-2 cells were analyzed. The isolates did not present more than one positive virulence-related trait simultaneously. In particular, it is important to highlight that the adhesion capacity to the model of intestinal barrier was extremely low for all of them. According to the results obtained, further studies would be of interest for the possible use of these promising yeasts as biocontrol agents against fungi in food.

Identification of Single Yeast Budding Using Impedance Cytometry with a Narrow Electrode Span.

Impedance cytometry is wildly used in single-cell detection, and its sensitivity is essential for determining the status of single cells. In this work, we focus on the effect of electrode gap on detection sensitivity. Through comparing the electrode span of 1 µm and 5 µm, our work shows that narrowing the electrode span could greatly improve detection sensitivity. The mechanism underlying the sensitivity improvement was analyzed via numerical simulation. The small electrode gap (1 µm) allows the electric field to concentrate near the detection area, resulting in a high sensitivity for tiny particles. This finding is also verified with the mixture suspension of 1 µm and 3 µm polystyrene beads. As a result, the electrodes with 1 µm gap can detect more 1 µm beads in the suspension than electrodes with 5 µm gap. Additionally, for single yeast cells analysis, it is found that impedance cytometry with 1 µm electrodes gap can easily distinguish budding yeast cells, which cannot be realized by the impedance cytometry with 5 µm electrodes gap. All experimental results support that narrowing the electrode gap is necessary for tiny particle detection, which is an important step in the development of submicron and nanoscale impedance cytometry.