Multiple Yeast Species Research Articles

From yeast screening for suitability as single cell protein to fed-batch cultures.

Fed-batch cultures have rarely been used in single cell protein (SCP) research. This work evaluated multiple yeast species for suitability as SCP cultivated using glucose- and sucrose-based substrate and performed in-depth studies of fed-batch SCP cultivation kinetics for selected yeasts, including determination of specific crude nitrogen-to-protein conversion factors. SCP was cultivated using fully synthetic media in flask batch or bioreactor fed-batch cultures. Crude nitrogen and nucleic acid content were determined using the Dumas method and fluorescence assay kits, respectively. C. utilis compared favorably to other yeasts in flask batch cultures in terms of process yield (0.52 ± 0.01 gxgs-1) and crude nitrogen content (10.0 ± 0.5 and 9.9 ± 0.5%CDW for glucose and sucrose, respectively). This is the first time biomass composition data was reported for SCP cultivated in fed-batch mode. C. utilis crude nitrogen content was consistent across the tested conditions (protein content stabilized around 50%CDW in fed-batch), while that of the benchmark yeast S. cerevisiae was higher in batch cultures and at the beginning of fed-batch relative to the end (protein content decreased over time and stabilized around 43%CDW). Total nucleic acid content of the yeasts was similar (6.8%CDW and 6.3%CDW, for C. utilis and S. cerevisiae, respectively), with crude nitrogen-to-protein conversion factors of 4.97 and 5.80. This study demonstrated the suitability of C. utilis as SCP, notably the robustness of its crude nitrogen content (as an indicator of protein content) across batch and fed-batch conditions, compared to that of the benchmark yeast S. cerevisiae.

Quantifying turgor pressure in budding and fission yeasts based upon osmotic properties

Walled cells, such as plants, fungi, and bacteria cells, possess a high internal hydrostatic pressure, termed turgor pressure, that drives volume growth and contributes to cell shape determination. Rigorous measurement of turgor pressure, however, remains challenging, and reliable quantitative measurements, even in budding yeast are still lacking. Here, we present a simple and robust experimental approach to access turgor pressure in yeasts based upon the determination of isotonic concentration using protoplasts as osmometers. We propose three methods to identify the isotonic condition – three-dimensional cell volume, cytoplasmic fluorophore intensity, and mobility of a cytGEMs nano-rheology probe – that all yield consistent values. Our results provide turgor pressure estimates of 1.0 ± 0.1 MPa for Schizosaccharomyces pombe, 0.49 ± 0.01 MPa for Schizosaccharomyces japonicus, 0.5 ± 0.1 MPa for Saccharomyces cerevisiae W303a and 0.31 ± 0.03 MPa for Saccharomyces cerevisiae BY4741. Large differences in turgor pressure and nano-rheology measurements between the Saccharomyces cerevisiae strains demonstrate how fundamental biophysical parameters can vary even among wild-type strains of the same species. These side-by-side measurements of turgor pressure in multiple yeast species provide critical values for quantitative studies on cellular mechanics and comparative evolution.

Saccharomyces cerevisiae wine strains show a wide range of competitive abilities and differential nutrient uptake behavior in co-culture with S. kudriavzevii

The wine industry has implemented complex starters with multiple yeast species as an efficient method to improve certain wine properties. Strains’ competitive fitness becomes essential for its use in such cases. In the present work, we studied this trait in 60 S. cerevisiae strains from different origins, co-inoculated with a S. kudriavzevii strain, and confirmed it to be associated with the strains' origin. To gather deeper knowledge about the characteristics of strains with highly competitive ability versus the rest, microfermentations using representative strains from each group were performed and the carbon and nitrogen sources uptake was analysed. Our results demonstrate that despite wine strains being the subclade with the highest competitive ability, they present a wide range of behaviors as well as nutrient uptake dynamics, which points to a heterogeneous nature of domestication processes. An interesting strategy was observed in the highly competitive strains (GRE and QA23), the nitrogen sources uptake in the competition was accelerated and the sugar fermentation was slowing despite the fermentation finish at the same time. Therefore, this competition study, using particular combinations of strains, expands the knowledge in the field of the usage of mixed starters in wine manufactured products.

Multiplex size marker (YEAST PLEX) for rapid and accurate identification of pathogenic yeasts.

BackgroundMultiple yeast species can cause human disease, involving superficial to deep‐seated infections. Treatment of these infections depends on the accurate identification of causative agents; however, reliable methods are not available in many laboratories, especially not in resource‐limited settings. Here, a new multiplex assay for rapid and low‐cost identification of pathogenic yeasts is described.MethodsA two‐step multiplex assay named YEAST PLEX that comprises of four tubes and identifies 17 clinically important common to rare yeasts was designed and evaluated. The set also provides PCR amplicon of unidentified species for direct sequencing. The specificity of YEAST PLEX was tested using 28 reference strains belonging to 17 species and 101 DNA samples of clinically important non‐target bacteria, parasites, and fungi as well as human genomic DNA. The method was further analyzed using 203 previously identified and 89 unknown clinical yeast isolates. Moreover, the method was tested for its ability to identify mixed yeast colonies by using 18 mixed suspensions of two or three species.ResultsYEAST PLEX was able to identify all the target species without any non‐specific PCR products. When compared to PCR‐sequencing/MALDI‐TOF, the results of YEAST PLEX were in 100% agreement. Regarding the 89 unknown clinical isolates, random isolates were selected and subjected to PCR‐sequencing. The results of sequencing were in agreement with those of YEAST PLEX. Furthermore, this method was able to correctly identify all yeasts in mixed suspensions.ConclusionYEAST PLEX is an accurate, low‐cost, and rapid method for identification of yeasts, with applicability, especially in developing countries.

Uncovering de novo gene birth in yeast using deep transcriptomics

De novo gene origination has been recently established as an important mechanism for the formation of new genes. In organisms with a large genome, intergenic and intronic regions provide plenty of raw material for new transcriptional events to occur, but little is know about how de novo transcripts originate in more densely-packed genomes. Here, we identify 213 de novo originated transcripts in Saccharomyces cerevisiae using deep transcriptomics and genomic synteny information from multiple yeast species grown in two different conditions. We find that about half of the de novo transcripts are expressed from regions which already harbor other genes in the opposite orientation; these transcripts show similar expression changes in response to stress as their overlapping counterparts, and some appear to translate small proteins. Thus, a large fraction of de novo genes in yeast are likely to co-evolve with already existing genes.

1272. Efficacy of a Non-Peptide, Small Molecule Mimic of Host Defense Proteins in Mouse Models of Disseminated Candidiasis and Aspergillosis

BackgroundWe are developing a series of small nonpeptide mimics of host defense proteins (smHDPs) for antifungal applications. MICs < 0.1 µg/ ml have been demonstrated against multiple yeast and mold species. Their potential therapeutic utility has been evaluated in animal models of disseminated fungal infections.MethodsSusceptibility testing against clinical isolates of Candida albicans (CA) and Aspergillus fumigatus (AF) was done according to CLSI guidelines. Cytotoxicity (CC50) in mouse 3T3 and human HepG2 cells was determined in an MTS assay (Promega Cell Titer 96). For candidiasis, neutropenic CD-1 mice were infected IV with 3.5 x 104 CFU CA and test agents were administered subcutaneously (SC) once (QD) or twice (BID) daily beginning 2 hrs post-infection (PI). The positive control was fluconazole (20 mg/kg PO QD). Kidney burdens were measured at 24 hrs PI (n = 5/grp) and survival was measured at 2 weeks after 5 days of treatment (n = 8/grp). For aspergillosis, neutropenic CD-1 mice were infected IV with 4.5 log10 spores AF and test agents were administered SC BID for 5 days beginning 24 hrs PI. The positive control was posaconazole (20 mg/kg PO QD). Liver and kidney fungal burdens were measured 24 hrs after the last dose (n = 10/grp).ResultsThe lead smHDP, FC-5096, has MICs of 0.08 and 0.024 ug/ml, respectively, against the CA and AF clinical isolate strains used in the mouse efficacy studies. Selectivity for antifungal vs. mammalian cell cytotoxicity (MIC/CC50) was >1,000 fold. In the disseminated candidiasis model, FC-5096 significantly reduced fungal kidney burdens relative to untreated mice to levels found at treatment onset (P < 0.0001). Full survival over 2 weeks was observed after 5 days of BID treatment with FC-5096. All untreated mice succumbed between days 3 – 6 PI. Efficacy was comparable to fluconazole. In the disseminated aspergillosis model, FC-5096 produced up to 2.5 log10 reductions in fungal liver burdens and efficacy was significantly better than posaconazole (P = 0.0251). In kidney, both FC-5096 and posaconazole caused > 1.6 log10 reductions in fungal burdens that exceeded the limit of detection.ConclusionThe high antifungal potency, low cytotoxicity and robust in vivo efficacy support further study of FC-5096 for clinical development.DisclosuresRichard W. Scott, PhD, Fox Chase Chemical Diversity Center (Employee) Simon DP Baugh, PhD, Fox Chase Chemical Diversity Center (Employee) Mark E Pulse, MS, Fox Chase Chemical Diversity Center (Independent Contractor)

Synthetic hybrids of six yeast species

Allopolyploidy generates diversity by increasing the number of copies and sources of chromosomes. Many of the best-known evolutionary radiations, crops, and industrial organisms are ancient or recent allopolyploids. Allopolyploidy promotes differentiation and facilitates adaptation to new environments, but the tools to test its limits are lacking. Here we develop an iterative method of Hybrid Production (iHyPr) to combine the genomes of multiple budding yeast species, generating Saccharomyces allopolyploids of at least six species. When making synthetic hybrids, chromosomal instability and cell size increase dramatically as additional copies of the genome are added. The six-species hybrids initially grow slowly, but they rapidly regain fitness and adapt, even as they retain traits from multiple species. These new synthetic yeast hybrids and the iHyPr method have potential applications for the study of polyploidy, genome stability, chromosome segregation, and bioenergy.

High Complexity and Degree of Genetic Variation in Brettanomyces bruxellensis Population.

Genome-wide characterization of genetic variants of a large population of individuals within the same species is essential to have a deeper insight into its evolutionary history as well as the genotype–phenotype relationship. Population genomic surveys have been performed in multiple yeast species, including the two model organisms, Saccharomyces cerevisiae and Schizosaccharomyces pombe. In this context, we sought to characterize at the population level the Brettanomyces bruxellensis yeast species, which is a major cause of wine spoilage and can contribute to the specific flavor profile of some Belgium beers. We have completely sequenced the genome of 53 B. bruxellensis strains isolated worldwide. The annotation of the reference genome allowed us to define the gene content of this species. As previously suggested, our genomic data clearly highlighted that genetic diversity variation is related to ploidy level, which is variable in the B. bruxellensis species. Genomes are punctuated by multiple loss-of-heterozygosity regions, whereas aneuploidies as well as segmental duplications are uncommon. Interestingly, triploid genomes are more prone to gene copy number variation than diploids. Finally, the pangenome of the species was reconstructed and was found to be small with few accessory genes compared with S. cerevisiae. The pangenome is composed of 5,409 ORFs (open reading frames) among which 5,106 core ORFs and 303 ORFs that are variable within the population. All these results highlight the different trajectories of species evolution and consequently the interest of establishing population genomic surveys in more populations.

Type 2 diabetes mellitus and oral Candida colonization: Analysis of risk factors in a Sri Lankan cohort

Aims: Oral candidiasis is a major oral manifestation of uncontrolled diabetes mellitus, and a number of cofactors are associated with the pathogenesis of this infection. Here, we describe the prevalence of oral Candida in a Sri Lankan cohort of type 2 diabetes mellitus and risk factors that predispose them to this common fungal infection.Methods: A case–control study was conducted in 250 diabetics with type 2 diabetes and 81 nondiabetic controls. Clinical and demographic data were collected using an interviewer administered questionnaire, and patient records. Oral rinse samples were collected to determine the candidal carriage, and the resultant yeast growth was quantified and speciated using multiplex-PCR and phenotypic analyses. Chi-square test (χ2 test) and Fisher exact test were used for the determination of the significant relationships between risk factors and oral candidiasis.Results: The oral prevalence of Candida species among both groups was similar (81%) although a significantly higher proportion of diabetics (32.8%) yielded >2000 CFU/mL of yeasts compared with only 12.3% of the healthy controls (p < .05). Significant associations were noted between oral candidal carriage amongst diabetics, and (i) denture wearing, (ii) female gender and (iii) cigarette smoking (all, p < .05). Amongst both groups, C.albicans was the most common Candida species isolated followed by C. parapsilosis, C. tropicalis and C. glabrata.Conclusions: The oral infestation of Candida in our Sri Lankan cohort of diabetics is significantly higher than their healthy counterparts, and co-carriage of multiple yeast species is a common finding in the study population. As there are no previous such reports of the latter phenomenon particularly from the Asian region it is noteworthy, mainly in view of the recent data on the emergence of drug-resistant yeast species the world over.

Dynamic Changes in Yeast Phosphatase Families Allow for Specialization in Phosphate and Thiamine Starvation.

Convergent evolution is often due to selective pressures generating a similar phenotype. We observe relatively recent duplications in a spectrum of Saccharomycetaceae yeast species resulting in multiple phosphatases that are regulated by different nutrient conditions – thiamine and phosphate starvation. This specialization is both transcriptional and at the level of phosphatase substrate specificity. In Candida glabrata, loss of the ancestral phosphatase family was compensated by the co-option of a different histidine phosphatase family with three paralogs. Using RNA-seq and functional assays, we identify one of these paralogs, CgPMU3, as a thiamine phosphatase. We further determine that the 81% identical paralog CgPMU2 does not encode thiamine phosphatase activity; however, both are capable of cleaving the phosphatase substrate, 1-napthyl-phosphate. We functionally demonstrate that members of this family evolved novel enzymatic functions for phosphate and thiamine starvation, and are regulated transcriptionally by either nutrient condition, and observe similar trends in other yeast species. This independent, parallel evolution involving two different families of histidine phosphatases suggests that there were likely similar selective pressures on multiple yeast species to recycle thiamine and phosphate. In this work, we focused on duplication and specialization, but there is also repeated loss of phosphatases, indicating that the expansion and contraction of the phosphatase family is dynamic in many Ascomycetes. The dynamic evolution of the phosphatase gene families is perhaps just one example of how gene duplication, co-option, and transcriptional and functional specialization together allow species to adapt to their environment with existing genetic resources.

Repeated Cis-Regulatory Tuning of a Metabolic Bottleneck Gene during Evolution.

Repeated evolutionary events imply underlying genetic constraints that can make evolutionary mechanisms predictable. Morphological traits are thought to evolve frequently through cis-regulatory changes because these mechanisms bypass constraints in pleiotropic genes that are reused during development. In contrast, the constraints acting on metabolic traits during evolution are less well studied. Here we show how a metabolic bottleneck gene has repeatedly adopted similar cis-regulatory solutions during evolution, likely due to its pleiotropic role integrating flux from multiple metabolic pathways. Specifically, the genes encoding phosphoglucomutase activity (PGM1/PGM2), which connect GALactose catabolism to glycolysis, have gained and lost direct regulation by the transcription factor Gal4 several times during yeast evolution. Through targeted mutations of predicted Gal4-binding sites in yeast genomes, we show this galactose-mediated regulation of PGM1/2 supports vigorous growth on galactose in multiple yeast species, including Saccharomyces uvarum and Lachancea kluyveri. Furthermore, the addition of galactose-inducible PGM1 alone is sufficient to improve the growth on galactose of multiple species that lack this regulation, including Saccharomyces cerevisiae. The strong association between regulation of PGM1/2 by Gal4 even enables remarkably accurate predictions of galactose growth phenotypes between closely related species. This repeated mode of evolution suggests that this specific cis-regulatory connection is a common way that diverse yeasts can govern flux through the pathway, likely due to the constraints imposed by this pleiotropic bottleneck gene. Since metabolic pathways are highly interconnected, we argue that cis-regulatory evolution might be widespread at pleiotropic genes that control metabolic bottlenecks and intersections.

Genome editing in Kluyveromyces and Ogataea yeasts using a broad-host-range Cas9/gRNA co-expression plasmid.

While CRISPR-Cas9-mediated genome editing has transformed yeast research, current plasmids and cassettes for Cas9 and guide-RNA expression are species specific. CRISPR tools that function in multiple yeast species could contribute to the intensifying research on non-conventional yeasts. A plasmid carrying a pangenomic origin of replication and two constitutive expression cassettes for Cas9 and ribozyme-flanked gRNAs was constructed. Its functionality was tested by analyzing inactivation of the ADE2 gene in four yeast species. In two Kluyveromyces species, near-perfect targeting (≥96%) and homologous repair (HR) were observed in at least 24% of transformants. In two Ogataea species, Ade− mutants were not observed directly after transformation, but prolonged incubation of transformed cells resulted in targeting efficiencies of 9% to 63% mediated by non-homologous end joining (NHEJ). In an Ogataea parapolymorpha ku80 mutant, deletion of OpADE2 mediated by HR was achieved, albeit at low efficiencies (<1%). Furthermore the expression of a dual polycistronic gRNA array enabled simultaneous interruption of OpADE2 and OpYNR1 demonstrating flexibility of ribozyme-flanked gRNA design for multiplexing. While prevalence of NHEJ prevented HR-mediated editing in Ogataea, such targeted editing was possible in Kluyveromyces. This broad-host-range CRISPR/gRNA system may contribute to exploration of Cas9-mediated genome editing in other Saccharomycotina yeasts.

Conserved non-AUG uORFs revealed by a novel regression analysis of ribosome profiling data.

Upstream open reading frames (uORFs), located in transcript leaders (5′ UTRs), are potent cis-acting regulators of translation and mRNA turnover. Recent genome-wide ribosome profiling studies suggest that thousands of uORFs initiate with non-AUG start codons. Although intriguing, these non-AUG uORF predictions have been made without statistical control or validation; thus, the importance of these elements remains to be demonstrated. To address this, we took a comparative genomics approach to study AUG and non-AUG uORFs. We mapped transcription leaders in multiple Saccharomyces yeast species and applied a novel machine learning algorithm (uORF-seqr) to ribosome profiling data to identify statistically significant uORFs. We found that AUG and non-AUG uORFs are both frequently found in Saccharomyces yeasts. Although most non-AUG uORFs are found in only one species, hundreds have either conserved sequence or position within Saccharomyces. uORFs initiating with UUG are particularly common and are shared between species at rates similar to that of AUG uORFs. However, non-AUG uORFs are translated less efficiently than AUG-uORFs and are less subject to removal via alternative transcription initiation under normal growth conditions. These results suggest that a subset of non-AUG uORFs may play important roles in regulating gene expression.

Comparative Analysis of Denaturing Gradient Gel Electrophoresis and Temporal Temperature Gradient Gel Electrophoresis Profiles as a Tool for the Differentiation of Candida Species.

Background:Candida species are usually opportunistic organisms that cause acute to chronic infections when conditions in the host are favorable. Accurate identification of Candida species is an essential pre-requisite for improved therapeutic strategy. Identification of Candida species by conventional methods is time-consuming with low sensitivity, yet molecular approaches have provided an alternative way for early diagnosis of invasive candidiasis. Denaturing gradient gel electrophoresis (DGGE) and temporal temperature gradient gel electrophoresis (TTGE) are polymerase chain reaction (PCR)-based approaches that are used for studying the community structure of microorganisms. By using these methods, simultaneous identification of multiple yeast species will be possible and reliable results will be obtained quickly.Objectives:In this study, DGGE and TTGE methods were set up and evaluated for the detection of different Candida species, and their results were compared.Materials and Methods:Five different Candida species were cultured on potato dextrose agar medium for 24 hours. Next, total DNA was extracted by the phenol-chloroform method. Two sets of primers, ITS3-GC/ITS4 and NL1-GC/LS2 were applied to amplify the desired regions. The amplified fragments were then used to analyze DGGE and TTGE profiles.Results:The results showed that NL1-GC/LS2 primer set could yield species-specific amplicons, which were well distinguished and allowed better species discrimination than that generated by the ITS3-GC/ITS4 primer set, in both DGGE and TTGE profiles. All five Candida species were discriminated by DGGE and TTGE using the NL1-GC/LS2 primer set.Conclusions:Comparison of DGGE and TTGE profiles obtained from NL1-GC/LS2 amplicons exhibited the same patterns. Although both DGGE and TTGE techniques are capable of detecting Candida species, TTGE is recommended because of easier performance and lower costs.

Niche construction initiates the evolution of mutualistic interactions.

Niche construction theory explains how organisms' niche modifications may feed back to affect their evolutionary trajectories. In theory, the evolution of other species accessing the same modified niche may also be affected. We propose that this niche construction may be a general mechanism driving the evolution of mutualisms. Drosophilid flies benefit from accessing yeast-infested fruits, but the consequences of this interaction for yeasts are unknown. We reveal high levels of variation among strains of Saccharomyces cerevisiae in their ability to modify fruits and attract Drosophila simulans. More attractive yeasts are dispersed more frequently, both in the lab and in the field, and flies associated with more attractive yeasts have higher fecundity. Although there may be multiple natural yeast and fly species interactions, our controlled assays in the lab and field provide evidence of a mutualistic interaction, facilitated by the yeast's niche modification.

Use of denaturing gradient gel electrophoresis for the identification of mixed oral yeasts in human saliva

A PCR-denaturing gradient gel electrophoresis (DGGE) method was established for the simultaneous presumptive identification of multiple yeast species commonly present in the oral cavity. Published primer sets targeting different regions of the Saccharomyces cerevisiae 26-28S rRNA gene (denoted primer sets N and U) and the 18S rRNA gene (primer set E) were evaluated with ten Candida and four non-Candida yeast species, and twenty Candida albicans isolates. Optimized PCR-DGGE conditions using primer set N were applied to presumptively identify, by band matching, yeasts in the saliva of 25 individuals. Identities were confirmed by DNA sequencing and compared with those using CHROMagar Candida culture. All primer sets yielded detectable DGGE bands for all species tested. Primer set N yielded mainly single bands and could distinguish all species examined, including differentiating Candida dubliniensis from C. albicans. Primer set U was less discriminatory among species but yielded multiple bands that distinguished subspecies groups within C. albicans. Primer set E gave poor yeast discrimination. DGGE analysis identified yeasts in 17 of the 25 saliva samples. Six saliva samples contained two yeast species: three contained C. albicans and three C. dubliniensis. C. dubliniensis was present alone in one saliva sample (total prevalence 16 %). CHROMagar culture detected yeasts in 16 of the yeast-containing saliva samples and did not enable identification of 7 yeast species identified by DGGE. In conclusion, DGGE identification of oral yeast species with primer set N is a relatively fast and reliable method for the simultaneous presumptive identification of mixed yeasts in oral saliva samples.

Detection of Yeasts in Blood Cultures by the Luminex xTAG Fungal Assay

A multiplex-PCR Luminex xMAP bead probe fluid array using xTAG analyte-specific reagents (multiplex xTAG fungal ASR assay) was employed for detection of clinically significant Candida species, Cryptococcus neoformans, Histoplasma capsulatum, and Blastomyces dermatitidis from blood cultures. We tested 132 blood cultures negative (n = 10) or positive (n = 97) for yeasts and/or bacteria (n = 25). The assay showed sensitivity and specificity of 100% and 99%, respectively. The xTAG fungal ASR assay is a rapid assay that allows simultaneous identification of multiple yeast species.

Evidence for an Additional Base-Pairing Element between the Telomeric Repeat and the Telomerase RNA Template in Kluyveromyces lactis and Other Yeasts

In all telomerases, the template region of the RNA subunit contains a region of telomere homology that is longer than the unit telomeric repeat. This allows a newly synthesized telomeric repeat to translocate back to the 3' end of the template prior to a second round of telomeric repeat synthesis. In the yeast Kluyveromyces lactis, the telomerase RNA (Ter1) template has 30 nucleotides of perfect homology to the 25-bp telomeric repeat. Here we provide strong evidence that three additional nucleotides at positions -2 through -4 present on the 3' side of the template form base-pairing interactions with telomeric DNA. Mutation of these bases can lead to opposite effects on telomere length depending on the sequence permutation of the template in a manner consistent with whether the mutation increases or decreases the base-pairing potential with the telomere. Additionally, mutations in the -2 and -3 positions that restore base-pairing potential can suppress corresponding sequence changes in the telomeric repeat. Finally, multiple other yeast species were found to also have telomerase RNAs that encode relatively long 7- to 10-nucleotide domains predicted to base pair, often with imperfect pairing, with telomeric DNA. We further demonstrate that K. lactis telomeric fragments produce banded patterns with a 25-bp periodicity. This indicates that K. lactis telomeres have preferred termination points within the 25-bp telomeric repeat.

Clash of the Genomes

Full-genome sequences of multiple yeast species offer exciting possibilities for the functional analysis of yeast evolution and speciation. Lee et al. (2008) now report that hybrid sterility between two yeast species is caused by incompatibility between a nuclear-encoded mitochondrial regulatory protein and its mitochondrial-encoded target gene.

Prevalence of oral Candida species in leprosy patients from Cambodia and Thailand

Leprosy is a chronic bacterial infection which may lead to significant orofacial morbidity. However, reports on the oral mycotic flora of leprosy patients are rare. The aim of the current study was to explore the oral yeast carriage in two groups of leprosy patients. 40 Cambodian (seven men, 33 women) and 48 Thai (14 men, 34 women) leprosy patients from Leprosy Rehabilitation Centre Khien Kleang, Phnom Penh, Cambodia and McKean Rehabilitation Center, Chiangmai, Thailand were randomly selected and their demographic data and clinical history were recorded. Tongue and palatal swabs of each patient were collected using sterile Fungi-Quick swabs (Hain Diagnostika, Nehren, Germany) and they were cultured aerobically on Sabouraud's dextrose agar and CHROMAgar (CHROMagar, Paris, France). Yeast were identified by germ tube, chlamydospore production, and assimilation tests (API 20C AUX, Bio-Merieux, Marcy l'Etoile, France) and reconfirmed using APILAB Plus system (Bio-Merieux). Two groups (Cambodian and Thai) had median age of 35 and 64 years. They had been with leprosy for median durations of 17.7 and 38.9 years (P<0.05), respectively. Overall yeast carriage in two cohorts were 80% and 93.75%. Candida albicans had highest carriage rate in either group (65.6%, 44.4%). Candida krusei and C. glabrata existed as second-line colonizers after C. albicans. Candida glabrata carriage was significantly higher in Thai patients (P<0.05). Multispecies carriage was seen in three Cambodian (9.4%) and five Thai (11.5%) patients. This study indicates high oral yeast carriage in leprosy patients. Candida albicans remains predominant while C. krusei and C. glabrata are second-line oral colonizers. Co-inhabitation of multiple yeast species is also noted in these patients' oral mycotic flora.