Prevalence and Antifungal Susceptibility of the Emerging Fungal Species, Candida nivariensis, Isolated in a Teaching Hospital in Poland

Influence of menthol on biofilm formation, ergosterol content, and cell surface hydrophobicity of Candida glabrata

Resistance to synthetic antifungals has become one of the leading public health challenges around the world. Accordingly, novel antifungal products like naturally occurring molecules can be one of the potential ways to reach efficient curative approaches to control candidiasis. This work evaluated the effect of menthol on cell surface hydrophobicity (CSH), biofilm formation, growth, and ergosterol content of Candida glabrata, a yeast with a high resistance against antifungal agents. Disc diffusion method (susceptibility to synthetic antifungals), broth micro-dilution method (Susceptibility to menthol), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide reduction assay (biofilm formation), High-performance liquid chromatography (HPLC) technique (ergosterol content), and adherence to n-hexadecane (CSH) were employed to determine the influence of menthol against C. glabrata isolates. The minimum inhibitory concentration (MIC) range of menthol versus C. glabrata was 1250-5000 µg/mL (mean ± SD: 3375 ± 1375 µg/mL). The mean rate of C. glabrata biofilm formation was decreased up to 97.67%, 81.15%, 71.21%, 63.72%, 47.53%, 26.31%, and 0.051% at 625, 1250, 2500, 5000, 10 000, 20 000, and 40 000 µg/mL concentrations, respectively. The percentages of CSH were significant in groups treated with MIC/2 (17.51 ± 5.52%) and MIC/4 (26 ± 5.87%) concentrations of menthol. Also, the percentage changes in membrane ergosterol were 15.97%, 45.34%, and 73.40% at 0.125, 0.25, and 0.5 mg/mL concentrations of menthol, respectively, in comparison with untreated control. The results showed the menthol impact versus sessile and planktonic C. glabrata cells, and the interference with ergosterol content, CSH, and biofilm formation, which made it a potent natural antifungal.

Candida species and oral mycobiota of patients clinically diagnosed with oral thrush

Overgrowth of Candida yeasts in the oral cavity may result in the development of oral thrush in immunocompromised individuals. This study analyzed the diversity and richness of the oral mycobiota of patients clinically diagnosed with oral thrush (OT), follow-up of oral thrush patients after antifungal therapy (AT), and healthy controls (HC). Oral rinse and oral swab samples were collected from 38 OT patients, 21 AT patients, and 41 healthy individuals (HC). Pellet from the oral rinse and oral swab were used for the isolation of oral Candida yeasts on Brilliance Candida Agar followed by molecular speciation. ITS1 amplicon sequencing using Illumina MiSeq was performed on DNA extracted from the oral rinse pellet of 16 OT, 7 AT, and 7 HC oral rinse samples. Trimmed sequence data were taxonomically grouped and analyzed using the CLC Microbial Genomics Module workflow. Candida yeasts were isolated at significantly higher rates from oral rinse and swab samples of OT (68.4%, p < 0.001) and AT (61.9%, p = 0.012) patients, as compared to HC (26.8%). Predominance of Candida albicans specifically, was noted in OT (60.5%, p < 0.001) and AT (42.9%, p = 0.006) vs. HC (9.8%), while non-albicans Candida species was dominant in HC. Analysis of oral mycobiota from OT patients showed the presence of 8 phyla, 222 genera, and 309 fungal species. Low alpha diversity (Shannon index, p = 0.006; Chao-1 biased corrected index, p = 0.01), varied beta diversity (Bray-Curtis, p = 0.01986; Jaccard, p = 0.02766; Weighted UniFrac, p = 0.00528), and increased relative abundance of C. albicans (p = 3.18E-02) was significantly associated with the oral mycobiota of OT vs. HC. This study supported that C. albicans is the main etiological agent in oral thrush and highlights the association of fungal biodiversity with the pathophysiology of oral thrush.

Overview on the Infections Related to Rare Candida species

Atypical Candida spp. infections are rising, mostly due to the increasing numbers of immunocompromised patients. The most common Candida spp. is still Candida albicans; however, in the last decades, there has been an increase in non-Candida albicans Candida species infections (e.g., Candida glabrata, Candida parapsilosis, and Candida tropicalis). Furthermore, in the last 10 years, the reports on uncommon yeasts, such as Candida lusitaniae, Candida intermedia, or Candida norvegensis, have also worryingly increased. This review summarizes the information, mostly related to the last decade, regarding the infections, diagnosis, treatment, and resistance of these uncommon Candida species. In general, there has been an increase in the number of articles associated with the incidence of these species. Additionally, in several cases, there was a suggestive antifungal resistance, particularly with azoles, which is troublesome for therapeutic success.

Refractory esophagitis caused by Candida nivariensis: second description of this yeast in Brazil and a literature review

Candida nivariensis caused refractory esophagitis in a 36-year-old Brazilian man coinfected with HIV and Leishmania. A literature review on this rare fungal pathogen is also presented. The diagnosis was made, and pathogen identification was performed using matrix-assisted laser desorption ionization-time of flight mass spectrometry and sequencing of the LSU/26S region. An antifungigram was performed using broth microdilution. A literature search of PubMed was performed. The causative agent, C. nivariensis, was resistant to fluconazole and voriconazole. The patient's condition worsened considerably, and he passed away. This is the second report of this Candida species in Brazil and the first case reported worldwide of refractory esophagitis in a patient coinfected with HIV and Leishmania. The case illustrates the importance of precise identification and antifungal susceptibility testing when isolating this emerging pathogen.

Antifungal Resistance in Clinical Isolates of Candida glabrata in Ibero-America

In different regions worldwide, there exists an intra-and inter-regional variability in the rates of resistance to antifungal agents in Candida glabrata, highlighting the importance of understanding the epidemiology and antifungal susceptibility profiles of C. glabrata in each region. However, in some regions, such as Ibero-America, limited data are available in this context. Therefore, in the present study, a systematic review was conducted to determine the antifungal resistance in C. glabrata in Ibero-America over the last five years. A literature search for articles published between January 2015 and December 2020 was conducted without language restrictions, using the PubMed, Embase, Cochrane Library, and LILACS databases. The search terms that were used were "Candida glabrata" AND "antifungal resistance" AND "Country", and 22 publications were retrieved from different countries. The use of azoles (fluconazole, itraconazole, voriconazole, posaconazole, isavuconazole, ketoconazole, and miconazole) varied between 4.0% and 100%, and that of echinocandins (micafungin, caspofungin, and anidulafungin) between 1.1% and 10.0%. The limited information on this subject in the region of Ibero-America emphasizes the need to identify the pathogens at the species level and perform antifungal susceptibility tests that may lead to the appropriate use of these drugs and the optimal doses in order to avoid the development of antifungal resistance or multi-resistance.

Candida glabrata Antifungal Resistance and Virulence Factors, a Perfect Pathogenic Combination

In recent years, a progressive increase in the incidence of invasive fungal infections (IFIs) caused by Candida glabrata has been observed. The objective of this literature review was to study the epidemiology, drug resistance, and virulence factors associated with the C. glabrata complex. For this purpose, a systematic review (January 2001-February 2021) was conducted on the PubMed, Scielo, and Cochrane search engines with the following terms: "C. glabrata complex (C. glabrata sensu stricto, C. nivariensis, C. bracarensis)" associated with "pathogenicity" or "epidemiology" or "antibiotics resistance" or "virulence factors" with language restrictions of English and Spanish. One hundred and ninety-nine articles were found during the search. Various mechanisms of drug resistance to azoles, polyenes, and echinocandins were found for the C. glabrata complex, depending on the geographical region. Among the mechanisms found are the overexpression of drug transporters, gene mutations that alter thermotolerance, the generation of hypervirulence due to increased adhesion factors, and modifications in vital enzymes that produce cell wall proteins that prevent the activity of drugs designed for its inhibition. In addition, it was observed that the C. glabrata complex has virulence factors such as the production of proteases, phospholipases, and hemolysins, and the formation of biofilms that allows the complex to evade the host immune response and generate fungal resistance. Because of this, the C. glabrata complex possesses a perfect pathogenetic combination for the invasion of the immunocompromised host.

First Report of a Case of Ocular Infection Caused by Purpureocillium lilacinum in Poland

This report describes the first case of an ocular infection induced by Purpureocillium lilacinum in Poland. The patient was a 51-year-old immunocompetent contact lens user who suffered from subacute keratitis and progressive granulomatous uveitis. He underwent penetrating keratoplasty for corneal perforation, followed by cataract surgery due to rapid uveitic cataract. A few weeks later, intraocular lens removal and pars plana vitrectomy were necessary due to endophthalmitis. The patient was treated with topical, systemic, and intravitreal voriconazole with improvement; however, the visual outcome was poor. The pathogen was identified by MALDI-TOF MS.

First Isolation of Candida nivariensis, an Emerging Fungal Pathogen, in Kuwait

OBJECTIVE

C. nivariensis is a rare Candida species which is phenotypically closely related to Candida glabrata and Candida bracarensis. The 3 species form the C. glabrata sensu lato complex. Here, we describe the first isolation and characterization of a C. nivariensis isolate cultured from the tracheal aspirate obtained from a young man in Kuwait.

MATERIALS AND METHODS

The yeast isolate was initially tested by VITEK 2 followed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and multiplex PCR. The identification was confirmed by sequencing of internal transcribed spacer (ITS) region of rDNA. Antifungal susceptibility testing was performed by Etest, and phylogenetic comparison with other international strains was carried out by using MEGA version 7 software.

RESULTS

The C. nivariensis isolate was misidentified by VITEK 2, but correctly identified by MALDI-TOF MS with updated software and multiplex PCR. The identity was confirmed by sequence comparisons of ITS region of rDNA. Antifungal susceptibility testing revealed high minimum inhibitory concentration (MIC) against fluconazole, but low MICs against amphotericin B and echinocandins. Phylogenetically, our isolate was closely related to Indian isolates.

CONCLUSIONS

This report extends the geographic distribution of C. nivariensis to the Arabian Peninsula. MALDI-TOF MS with updated software and molecular tests are needed to correctly identify C. nivariensis. Since C. nivariensis may exhibit reduced susceptibility to antifungal agents, accurate identification and antifungal susceptibility testing are essential, particularly for isolates from sterile sites, for optimal patient management.

Molecular Investigation of Etiologic Agents Causing Vulvovaginal Candidiasis

Background: Vulvovaginal candidiasis (VVC) is an ordinary infection caused by Candida species. Meanwhile, a shift towards non-albicans Candida (NAC) species has been detected in VVC patients. Objectives: This study aimed at molecular identification of Candida isolates, causing VVC. Methods: Vaginal secretion samples of 320 non-pregnant vaginitis patients at Shahid Akbar-Abadi Obstetrics and Gynecology Hospital in Tehran (Iran) were collected. Samples were evaluated using mycological and molecular approaches. Vaginitis isolates were analyzed with the PCR using NL1 and NL4 primers, and the D1/D2 region of the large-subunit rRNA gene was amplified and sequenced. Results: In total, 100 Candida isolates were identified from VVC and recurrent vulvovaginal candidiasis (RVVC). Candida albicans was the most frequent (51%), followed by C. glabrata (36%), C. krusei (Pichia kudriavzevii) (8%), and C. kefyr (Kluyveromyces marxianus) (5%). 51 and 49% of isolates had C. albicans and NAC, respectively. Conclusions: Candida albicans and C. glabrata were the most common agents of vulvovaginal candidiasis. NAC spp. (49%) was found as an important agent associated with VVC.

Candida nivariensis: Identification strategy in mycological laboratories

Candida nivariensis is a cryptic fungal species classified within the Candida glabrata complex. It was described for the first time in 2005 by the means of DNA sequencing. We report a rare case of C. nivariensis deep-seated infection occurring in a 77-year-old man hospitalized for cysto-prostatectomy. Phenotypic testing based on the direct examination and the macroscopic features of the in vitro culture initially suggested C. glabrata species, while MALDI-TOF mass spectrometry enables correct identification. The isolate was found resistant to fluconazole, like in almost 20% of the reported cases. Herein, we present our practical strategy to reliably characterize this rare cryptic species. To date, MALDI-TOF mass spectrometry-based analysis showed very good results for such a purpose.