Prevalence of Candida nivariensis and Candida bracarensis in vulvovaginal Candidiasis

Three cases of vulvovaginal candidiasis due to Candida nivariensis

Candida nivariensis is emerging as a highly resistant species of the Candida glabrata complex causing invasive and mucocutaneous infections. In this study, three cases of vulvovaginal candidiasis caused by C. nivariensis are described and identified by Internal Transcribed Spacer 1-2 sequencing. All isolates were susceptible in vitro to anidulafungin, micafungin, caspofungin, 5-flucytosine, posaconazole, voriconazole, itraconazole, amphotericin B, and showed dose-dependent susceptibility to fluconazole. In two patients, three doses of oral fluconazole were effective, while one patient developed clinical fluconazole resistance with a new relapse after 6 months. Increasing the weekly dose of fluconazole showed to be effective in this patient.

High diversity of yeast species and strains responsible for vulvovaginal candidiasis in South-East Gabon

OBJECTIVES

Candida albicans generally remains the principal pathogenic yeast responsible for vulvovaginal candidiasis (VVC), although with variable prevalence. In this study, we evaluated the evolution of the prevalence of the non-Candida albicans Candida (NCAC) species and investigated the genotypic diversity and the population genetic structure of the circulating C. albicans strains associated with VVC in the vicinity of Franceville (Gabon).

METHODS

A total of 110 independent isolates were identified using both MALDI-TOF MS and conventional techniques. The population genetic structure of the C. albicans strains was determined by multiple locus variable-number tandem repeat analysis using 4 microsatellite markers.

RESULTS

The mean and median age of the patients was 31 years. Seven patients had a mixed infection. C. albicans accounted for 62 % (n=68) of the total isolates. NCAC were dominated by C. glabrata, followed by P. kudriavzevii, C. parapsilosis, C. tropicalis, M. guilliermondii, and C. nivariensis. The cluster analysis revealed a high diversity, with a total of 50 different genotypes. The most represented genotype was shared by only four strains, while the vast majority (39 strains) had a unique MLVA pattern. Geographic clusters were not detected.

CONCLUSION

The study provides information on species distribution and possible changing epidemiology while reporting for the first time C. nivariensis in VVC in Africa. This study is also the first to investigate the genotypic diversity of the circulating C. albicans strains associated with VVC in Central Africa. Such analyses would help understand the molecular epidemiology of C. albicans.

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.

Analysis of Biofilm-Related Genes and Antifungal Susceptibility Pattern of Vaginal Candida albicans and Non-Candida albicans Species

Background

Vulvovaginal candidiasis caused by Candida species is a prevalent fungal infection among women. It is believed that the pathogenesis of Candida species is linked with the production of biofilm which is considered a virulence factor for this organism. The aim of this study was molecular identification, antifungal susceptibility, biomass quantification of biofilm, and detection of virulence markers of Candida species.

Methods

We investigated the molecular identification of 70 vaginal isolates of Candida species, antifungal resistance to amphotericin B, fluconazole, itraconazole, and voriconazole according to CLSI M27-A3 and M27-S4, biofilm formation, and frequency analysis of biofilm-related ALS1, ALS3, and HWP1 genes.

Results

Our findings showed that the most common yeast isolated from vaginal discharge was C. albicans (67%), followed by the non-Candida albicans species (33%). All C. albicans complex isolates were confirmed as C. albicans by HWP-PCR, and all isolates of the C. glabrata complex were revealed to be C. glabrata sensu stricto using the multiplex PCR method. FLC resistance was observed in 23.4% of C. albicans and 7.7% of C. glabrata. The resistance rate to ITC was found in 10.6% of C. albicans. The frequency of ALS1, ALS3, and HWP1 genes among Candida species was 67.1%, 80%, and 81.4%, respectively. Biofilm formation was observed in 54.3% of Candida species, and the highest frequency detected as a virulence factor was for the ALS3 gene (97.3%) in biofilm-forming species. Discussion. Our results showed the importance of molecular epidemiology studies, investigating antifungal susceptibility profiles, and understanding the role of biofilm-related virulence markers in the pathogenesis of Candida strains.

Molecular identification and antifungal susceptibility profile of yeast from vulvovaginal candidiasis

BACKGROUND

Accurate identification Candida is important for successful therapy and epidemiology study. The aim of research is to study API 20C yeast identification system identification rate by using molecular identification as gold standard and tested the antifungal susceptibility of Candida from patients with vulvovaginal candidiasis (VVC).

METHODS

In total, 3574 yeast isolates were obtained from patients with VVC. API 20C yeast identification, molecular identification and in vitro antifungal susceptibility were performed.

RESULTS

C. albicans was the predominant Candida species [2748 isolates, 76.9%] in VVC. The isolates from vaginal samples represented 22 species based on molecular identification. The API 20C system identifies only 11 of the species encountered during the study period. Based on the API 20C system, 3273 (91.78%) isolates were correctly identified to the species level. The correct identification rate of the API 20C system for rare yeast was 15.29% (26/170 isolates). Antifungal susceptibility was tested in a total of 1844 isolates of Candida from patients with VVC. C. albicans was susceptible to most of the tested antifungals. The MICs of azoles for C. glabrata were higher than those for C. albicans. The MICs of echinocandins for C. parapsilosis were higher than those for C. albicans.

CONCLUSIONS

The API 20C yeast identification system can be used to reliably identify the most common Candida species while molecular methods are necessary for the identification of closely related, emerging, and rare yeast species. The results from this study suggest that much of the previous studies on the epidemiology of VVC should be re-thought. C. albicans was susceptible to most of the tested antifungals.

New and Promising Chemotherapeutics for Emerging Infections Involving Drug-resistant Non-albicans Candida Species

Fungal infections are a veritable public health problem worldwide. The increasing number of patient populations at risk (e.g. transplanted individuals, cancer patients, and HIV-infected people), as well as the use of antifungal agents for prophylaxis in medicine, have favored the emergence of previously rare or newly identified fungal species. Indeed, novel antifungal resistance patterns have been observed, including environmental sources and the emergence of simultaneous resistance to different antifungal classes, especially in Candida spp., which are known for the multidrug-resistance (MDR) profile. In order to circumvent this alarming scenario, the international researchers' community is engaged in discovering new, potent, and promising compounds to be used in a near future to treat resistant fungal infections in hospital settings on a global scale. In this context, many compounds with antifungal action from both natural and synthetic sources are currently under clinical development, including those that target either ergosterol or β(1,3)-D-glucan, presenting clear evidence of pharmacologic/pharmacokinetic advantages over currently available drugs against these two well-known fungal target structures. Among these are the tetrazoles VT-1129, VT-1161, and VT-1598, the echinocandin CD101, and the glucan synthase inhibitor SCY-078. In this review, we compiled the most recent antifungal compounds that are currently in clinical trials of development and described the potential outcomes against emerging and rare Candida species, with a focus on C. auris, C. dubliniensis, C. glabrata, C. guilliermondii, C. haemulonii, and C. rugosa. In addition to possibly overcoming the limitations of currently available antifungals, new investigational chemical agents that can enhance the classic antifungal activity, thereby reversing previously resistant phenotypes, were also highlighted. While novel and increasingly MDR non-albicans Candida species continue to emerge worldwide, novel strategies for rapid identification and treatment are needed to combat these life-threatening opportunistic fungal infections.

Lack of detection of Candida nivariensis and Candida bracarensis among 440 clinical Candida glabrata sensu lato isolates in Kuwait

Occurrence of Candida nivariensis and Candida bracarensis, two species phenotypically similar to Candida glabrata sensu stricto, in human clinical samples from different geographical settings remains unknown. This study developed a low-cost multiplex PCR (mPCR) and three species-specific singleplex PCR assays. Reference strains of common Candida species were used during development and the performance of mPCR and singleplex PCR assays was evaluated with 440 clinical C. glabrata sensu lato isolates. The internal transcribed spacer (ITS) region of rDNA was also sequenced from 85 selected isolates and rDNA sequence variations were used for determining genetic relatedness among the isolates by using MEGA X software. Species-specific amplicons for C. glabrata (~360 bp), C. nivariensis (~250 bp) and C. bracarensis (~180 bp) were obtained in mPCR while no amplicon was obtained from other Candida species. The three singleplex PCR assays also yielded expected results with reference strains of Candida species. The mPCR amplified ~360 bp amplicon from all 440 C. glabrata sensu lato isolates thus identifying all clinical isolates in Kuwait as C. glabrata sensu stricto. The results of mPCR were confirmed for all 440 isolates as they yielded an amplicon only in C. glabrata sensu stricto-specific singleplex PCR assay. The rDNA sequence data identified 28 ITS haplotypes among 85 isolates with 18 isolates belonging to unique haplotypes and 67 isolates belonging to 10 cluster haplotypes. In conclusion, we have developed a simple, low-cost mPCR assay for rapid differentiation of C. glabrata sensu stricto from C. nivariensis and C. bracarensis. Our data obtained from a large collection of clinical C. glabrata sensu lato isolates show that C. nivariensis and C. bracarensis are rare pathogens in Kuwait. Considerable genetic diversity among C. glabrata sensu stricto isolates was also indicated by rDNA sequence analyses.

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

The data on susceptibility to antifungals of new species within Candida glabrata complex are limited. Our study was to enrich a global knowledge of yeast epidemiology and drug resistance. The study was focused on the identification of species within clinical isolates of the C. glabrata complex and on the determination of their resistance to antifungals. Four hundred forty-five clinical C. glabrata sensu lato strains were isolated from different clinical samples at routine mycological exams at the Infant Jesus Teaching Hospital in Warsaw. The identification of the most of tested isolates to species complex level was performed using the ID 32 C system. The identification of C. nivariensis and C. bracarensis species within the C. glabrata complex was performed by DNA sequencing. The MICs of amphotericin B, fluconazole, itraconazole, posaconazole, voriconazole, caspofungin, anidulafungin, and micafungin were determined by E-test. Twenty-four isolates did not have an ITS-1 region, characteristic of C. glabrata sensu stricto and their D1/D2 regions of the 26S rRNA were 99% homologous to C. nivariensis 26S rRNA. No strains of C. bracarensis were recovered. C. nivariensis strains were very susceptible to amphotericin B, anidulafungin, micafungin, and caspofungin. Ninety-two percent of C. nivariensis were resistant to itraconazole. The halves of the strains was resistant to posaconazole. Eighty-three percent of C. nivariensis were susceptible to voriconazole. None of the tested strains were susceptible to fluconazole. In the present study, none of the C. nivariensis strains were simultaneously resistant to azoles and echinocandins. C. nivariensis should be recognized as an emerging pathogen, resistant to azoles.

Usefulness of a multiplex PCR for the rapid identification of Candida glabrata species complex in Mexican clinical isolates

Candida glabrata complex includes three species identified through molecular biology methods: C. glabrata sensu stricto , C. nivariensis and C. bracarensis . In Mexico, the phenotypic methods are still used in the diagnosis; therefore, the presence of C. nivariensis and C. bracarensis among clinical isolates is still unknown. The aim of this study was to evaluate the utility of a multiplex PCR for the identification of the C. glabrata species complex. DNA samples from 92 clinical isolates that were previously identified through phenotypic characteristics as C. glabrata were amplified by four oligonucleotides (UNI-5.8S, GLA-f, BRA-f, and NIV-f) that generate amplicons of 397, 293 and 223-bp corresponding to C. glabrata sensu stricto , C. nivariensis , and C. bracarensis , respectively. The amplicon sequences were used to perform a phylogenetic analysis through the Maximum Likelihood method (MEGA6), including strains and reference sequences of species belonging to C. glabrata complex. In addition, recombination and linkage disequilibrium were estimated (DnaSP version 5.0) for C. glabrata sensu stricto isolate s . Eighty-eight isolates generated a 397-bp fragment and only in one isolate a 223-bp amplicon was observed. In the phylogenetic tree, the sequences of 397-bp were grouped with C. glabrata reference sequences , and the sequence of 223-bp was grouped with C. bracarensis reference sequences, corroborating the PCR identification. The number of recombination events for the isolates of C. glabrata sensu stricto was zero, suggesting a clonal population structure. Three isolates that did not amplify any of the expected fragments were identified as Saccharomyces cerevisiae through the sequencing of the D1/D2 domain region within the 28S rDNA gene. The multiplex PCR is a fast, cost-effective and reliable tool that can be used in clinical laboratories to identify C. glabrata complex species.

Candida species isolated from pigeon (Columbia livia) droppings may express virulence factors and resistance to azoles

Even though it is widely known that Cryptococcus spp. may transmit cryptococcosis trough aerosol formed when dried birds (mainly pigeons) droppings are dispersed and become airborne, little is known about the role of these birds in harboring other pathogenic yeasts in their gastrointestinal tract, feathers and beaks, specifically because these animals often stay and reproduce close or even above air conditioner units. Here we evaluated the prevalence of pathogenic yeasts isolated from pigeon droppings collected in the outside area of a University Hospital in Brazil. We also aimed to investigate the pathogenic potential and antifungal susceptibility of Candida species of medical interest isolated from these samples. Therefore, we performed the evaluation of virulence factors attributes expression in vitro, including the ability to adhere to human buccal epithelial cells and biofilm formation and to produce lytic enzymes, such as phospholipases, proteinases and hemolysins. Antifungal susceptibility testing against fluconazole, itraconazole, amphotericin and micafungin was also performed. The Candida genus was the most prevalent in our study, with several medically important species being isolated. Of note, these strains were able to express several virulence factors in vitro, clearly showing their pathogenic potential. Our study was able to demonstrate that Candida spp. isolated from pigeon droppings may express virulence factors in the same manner of clinical isolates, suggesting a pathogenic potential for these yeasts. The fact these strains were collected from the outside area of a tertiary hospital may be of interest, because they may be a source of infection, specifically to immunocompromised hosts.

Molecular characterization and antifungal susceptibility testing of Candida nivariensis from blood samples - an Iranian multicentre study and a review of the literature

PURPOSE

Identification of the emerging yeast species Candida nivariensis among presumptively identified Iranian Candida glabrata isolates.

METHODOLOGY

Clinical C. glabrata species complex isolates from blood (n=71; 33.3 %), urine (n=100; 46.9 %), vaginal swabs (n=20;9.4 %), BAL (n=10; 4.7 %), and sputum (n=12; 5.6 %) from Iran were investigated. Isolates were characterized by CHROMagar, multiplex PCRs, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), amplified fragment length polymorphism (AFLP) fingerprinting, internal transcribed spacer (ITS)/large subunit (LSU) rDNA and FKS1/FKS2 sequencing, and the European Committee on Antimicrobial Susceptibility Testing broth microdilution method. A comprehensive literature review was conducted and all the relevant clinical and microbiological data were collected.

RESULTS

Four C. nivariensis isolates were recovered from blood samples of three subjects and were all consistently identified by nine-plex PCR, Bruker MALDI-TOF MS, and LSU and ITS rDNA sequencing. AFLP genotyping clustered the isolates into two groups. Sequencing of the FKS1 and FKS2 hotspots showed no accountable amino acid substitutions. All isolates were susceptible to amphotericin B, fluconazole, itraconazole, posaconazole, voriconazole, anidulafungin and micafungin.

CONCLUSION

In total, 4 out of 213 clinical C. glabrata species complex candidemia isolates were C. nivariensis. Improvement of the BioMerieux Vitek MS database is required to accurately identify C. nivariensis and it is advised to alternatively use CHROMagar and/or PCR-based techniques. As other species within the Nakaseomyces clade may cause infection and showed high MIC values for antifungals, inclusion of their spectra into the MALDI-TOF MS database seems relevant. Due to developing resistance to fluconazole and insufficient efficacy of caspofungin, the combination of catheter removal plus treatment with caspofungin, or voriconazole, or micafungin might be effective for patients.

Prevalence of human pathogens of the clade Nakaseomyces in a culture collection-the first report on Candida bracarensis in Poland

Human pathogens belonging to the Nakaseomyces clade include Candida glabrata sensu stricto, Candida nivariensis and Candida bracarensis. Their highly similar phenotypic characteristics often lead to misidentification by conventional laboratory methods. Therefore, limited information on the true epidemiology of the Candida glabrata species complex is available. Due to life-threatening infections caused by these species, it is crucial to supplement this knowledge. The aim of the study was to estimate the prevalence of C. bracarensis and C. nivariensis in a culture collection of C. glabrata complex isolates. The study covered 353 isolates identified by biochemical methods as C. glabrata, collected from paediatric and adult patients hospitalised at four medical centres in Southern Poland. The multiplex PCR was used to identify the strains. Further species confirmation was performed via sequencing and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) analysis. One isolate was recognised as C. bracarensis (0.28%). To our knowledge, it is the first isolate in Poland. C. glabrata sensu stricto species has been confirmed for all the remaining isolates. No C. nivariensis was found. Our study has shown that the prevalence of C. nivariensis and C. bracarensis strains is infrequent. However, it should be emphasised that the incidence of these strains may differ locally and depend on environmental factors and the population.

Prevalence and antifungal susceptibility profiles of Candida glabrata, Candida parapsilosis and their close-related species in oral candidiasis

OBJECTIVE

To evaluate the importance of Candida glabrata, Candida parapsilosis and their close-related species, Candida bracarensis, Candida nivariensis, Candida metapsilosis and Candida orthopsilosis in patients with oral candidiasis and, to determine the in vitro activities of antifungal drugs currently used for the treatment.

METHODS

One hundred fourteen isolates of C. glabrata and 97 of C. parapsilosis, previously identified by conventional mycological methods, were analysed by molecular techniques. In vitro antifungal susceptibility to fluconazole, itraconazole, miconazole, and nystatin was evaluated by CLSI M44-A2 disk diffusion test, and by CLSI M27-A3 microdilution for fluconazole.

RESULTS

All C. glabrata isolates were identified as C. glabrata sensu stricto, 93 out of 97 C. parapsilosis isolates as C. parapsilosis sensu stricto, three as C. orthopsilosis and one as C. metapsilosis. Candida glabrata was mainly isolated in mixed cultures but C. parapsilosis complex was more frequent in pure culture. Candida metapsilosis and C. orthopsilosis were isolated as pure culture and both species were susceptible to all antifungal agents tested. Most C. glabrata isolates were susceptible to miconazole and nystatin, but resistant to fluconazole and itraconazole. Azole cross resistance was also observed. Candida parapsilosis isolates were susceptible to fluconazole although azole cross resistance to miconazole and itraconazole was observed.

CONCLUSION

This study highlights the importance of accurate identification and antifungal susceptibility testing of oral Candida isolates in order to have an in-depth understanding of the role of C. glabrata and C. parapsilosis in oral candidiasis.

First report of Candida bracarensis in Mexico: hydrolytic enzymes and antifungal susceptibility pattern

Candida bracarensis is an emerging cryptic species within the Candida glabrata clade. To date, little is known about its epidemiology, virulence, and antifungal susceptibility. This study documents the occurrence of C. bracarensis for the first time in Mexico and focuses on its in vitro production of hydrolytic enzymes, as well as antifungal susceptibility to echinocandins. This strain was isolated from a vaginal swab of a female with vulvovaginal candidosis; exhibited a very strong activity of aspartyl proteinase, phospholipase, and hemolysin; and was susceptible to caspofungin, anidulafungin, and micafungin (MIC = 0.031 μg/mL). Data obtained could contribute to the knowledge of the epidemiology and virulence attributes of this yeast as a fungal opportunistic human pathogen.

First description of Candida nivariensis in Brazil: antifungal susceptibility profile and potential virulence attributes

This study evaluated the antifungal susceptibility profile and the production of potential virulence attributes in a clinical strain of Candida nivariensis for the first time in Brazil, as identified by sequencing the internal transcribed spacer (ITS)1-5.8S-ITS2 region and D1/D2 domains of the 28S of the rDNA. For comparative purposes, tests were also performed with reference strains. All strains presented low planktonic minimal inhibitory concentrations (PMICs) to amphotericin B (AMB), caspofungin (CAS), and voriconazole. However, our strain showed elevated planktonic MICs to posaconazole (POS) and itraconazole, in addition to fluconazole resistance. Adherence to inert surfaces was conducted onto glass and polystyrene. The biofilm formation and antifungal susceptibility on biofilm-growing cells were evaluated by crystal violet staining and a XTT reduction assay. All fungal strains were able to bind both tested surfaces and form biofilm, with a binding preference to polystyrene (p < 0.001). AMB promoted significant reductions (≈50%) in biofilm production by our C. nivariensis strain using both methodologies. This reduction was also observed for CAS and POS, but only in the XTT assay. All strains were excellent protease producers and moderate phytase producers, but lipases were not detected. This study reinforces the pathogenic potential of C. nivariensis and its possible resistance profile to the azolic drugs generally used for candidiasis management.

Candida nivariensis as a New Emergent Agent of Vulvovaginal Candidiasis: Description of Cases and Review of Published Studies

Candida nivariensis is a new emergent agent related to human infections in the vaginal tract and other localizations, but the phenotypic characteristics are very similar to Candida glabrata and can be misidentified and underdiagnosed. We described four cases of vulvovaginitis identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and confirmed the results with PCR amplification and sequencing of the entire ITS genomic region (ITS1, ITS2 and 5.8 rRNA). We reinforce the need for new diagnostic tools for the correct identification of yeast infections.

Current methods for identifying clinically important cryptic Candida species

In recent years, the taxonomy of the most important pathogenic Candida species (Candida albicans, Candida parapsilosis and Candida glabrata) has undergone profound changes due to the description of new closely-related species. This has resulted in the establishment of cryptic species complexes difficult to recognize in clinical diagnostic laboratories. The identification of these novel Candida species seems to be clinically relevant because it is likely that they differ in virulence and drug resistance. Nevertheless, current phenotypic methods are not suitable to accurately distinguish all the species belonging to a specific cryptic complex and therefore their recognition still requires molecular methods. Since traditional mycological techniques have not been useful, a number of molecular based methods have recently been developed. These range from simple PCR-based methods to more sophisticated real-time PCR and/or MALDI-TOF methods. In this article, we review the current methods designed for discriminating among closely related Candida species by highlighting, in particular, the limits of the existing phenotypic tests and the development of rapid and specific molecular tools for their proper identification.