| Nakaseomyces glabratus | |
|---|---|
 | |
| Nakaseomyces glabratus 1600x | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Saccharomycetes |
| Order: | Saccharomycetales |
| Family: | Saccharomycetaceae |
| Genus: | Nakaseomyces |
| Species: | N. glabratus |
| Binomial name | |
| Nakaseomyces glabratus (H. W. Anderson) Sugita & Takashima (2022) | |
| Synonyms | |
Cryptococcus glabratusH.W.Anderson (1917) | |
Nakaseomyces glabratus is aspecies ofhaploidyeast of the genusNakaseomyces, previously known asCandida glabrata. Despite the fact that no sexual life cycle has been documented for this species,N. glabratus strains of both mating types are commonly found.[1]N. glabrata is generally acommensal of human mucosal tissues, but in today's era of wider humanimmunodeficiency from various causes (for example,therapeutic immunomodulation, longer survival with various comorbidities such asdiabetes, andHIV infection),N. glabratus is often the second or third most common cause ofcandidiasis as anopportunistic pathogen.[2] Infections caused byN. glabratus can affect theurogenital tract or even cause systemic infections by entrance of the fungal cells in the bloodstream (Candidemia), especially prevalent in immunocompromised patients.[2]
N. glabratus is of special relevance in nosocomial infections due to its innately highresistance toantifungal agents, specifically theazoles.[2] Besides its innate tolerance to antifungal drugs, other potential virulence factors contribute toN. glabratuspathogenicity. One of them is the expression of a series ofadhesins genes.[3] These genes, which inN. glabratus are mostly encoded in thesubtelomeric region of thechromosome, have their expression highly activated by environmental cues, so that the organism can adhere to biotic and abiotic surfaces in microbial mats. Adhesin expression is the suspected first mechanism by whichN. glabratus forms fungalbiofilms, proved to be more resistant to antifungals than theplanktonic cells.[4]
N. glabratus genome frequently undergoes rearrangements that are hypothesized to contribute to the improvement of this yeast's fitness towards exposure to stressful conditions, and some authors consider that this property is connected to the virulence potential of this yeast.[5]
Cultures are an effective method for identifying non-albicans vaginal infections. Urinalyses are less accurate in this process. The culture may take several days to grow, but the identification of the yeast species is quick once the yeast is isolated. Skin disease diagnosis is difficult, as cultures collected from swabs andbiopsies will test negative for fungus and a special assessment is required. Listed under the 'Rare Diseases' database on the NIH web site[verification needed],Torulopsis glabrata, orN. glabratus can also be found on the CDC's web site.[6] Although listed as the second most virulent yeast afterCandida albicans, the fungus is becoming more and more resistant to common treatments likefluconazole.N. glabratus resistance toEchinocandin is also increasing, leaving expensive and toxic antifungal treatments available for those infected.[6] Although high mortality rates are listed, assessment of the critical nature of a glabrata infection is a gray area.
N. glabratus ferments and assimilates onlyglucose andtrehalose, opposing toCandida species and this repertoire of sugar utilization is used by several commercially available kits for identification.[7]
A major phenotype and potential virulence factor thatN. glabratus possesses is low-level intrinsic resistance to theazole medications, which are the most commonly prescribed antifungal (antimycotic) medications. These medications, includingfluconazole andketoconazole, are "not effective in 15–20% of cases"[2] againstN. glabratus. It is still highly vulnerable to polyene medications such asamphotericin B andnystatin, along with variable vulnerability toflucytosine andcaspofungin. However, intravenous amphotericin B is a medication of last resort, causing among other side effects, chronickidney failure. Amphotericin B vaginal suppositories are used as an effective form of treatment in combination withboric acid capsules as they are not absorbed into the bloodstream.
A first-line treatment for vaginal infections may be the use ofterconazole 7-day cream. Several courses may be needed. The cure-rate for this treatment is approximately 40%. Recurrences are common, causing chronic infections and spread to other areas such as skin and scalp. Blood infections might be best assessed per symptoms if other areas are involved.
An experimental, but effective second-line treatment for chronic infections, is the use of boric acid. Compounding pharmacies can create boric acid vaginal suppositories. Use ofvitamin E oil may be used in conjunction to combat irritation.Amphotericin B vaginal suppositories have also been used in case studies to treat chronic infections, both symptomatic and asymptomatic.Borax andboric acid may be used for persistent scalp and skin infections.
N. glabratus is more closely related toSaccharomyces cerevisiae than toCandida species. In fact,N. glabratus belongs to the group ofNakaseomyces inside thewhole genome duplication clade withinSaccharomycetaceae.[8] The whole genome duplication event occurred about 90 million years ago, whereas phylogenetic studies indicate that the common ancestor betweenN. glabratus andC. albicans is dated between 200 and 300 million years ago. The largest phylogenetic study to date aboutSaccharomycotina, also known as budding yeasts, indicated in 2018 that the (currently construed) genusCandida is found inPichiaceae, CUG-Ser1 clade,Phaffomycetaceae andSaccharomycetaceae. Consequently, despite that the nameCandida evokes a unitary notion ofcandidiasis, the pathogenic power of some budding yeasts is aparaphyletic trait shared by several subphyla with different kinds of metabolism.[9]
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