Debaryomyces hansenii (Candida famata), a Rare Human Fungal Pathogen Often Misidentified as Pichia guilliermondii (Candida guilliermondii) (original) (raw)
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Molecular identification of Pichia guilliermondii, Debaryomyces hansenii and Candida palmioleophila
Genetics and Molecular Biology, 2012
Traditional phenotypic methods and commercial kits based on carbohydrate assimilation patterns are unable to consistently distinguish among isolates of Pichia guilliermondii, Debaryomyces hansenii and Candida palmioleophila. As result, these species are often misidentified. In this work, we established a reliable method for the identification/differentiation of these species. Our assay was validated by DNA sequencing of the polymorphic region used in a real-time PCR assay driven by species-specific probes targeted to the fungal ITS 1 region. This assay provides a new tool for pathogen identification and for epidemiological, drug resistance and virulence studies of these organisms.
Identificación rápida de Candida dubliniensis mediante la prueba Bichro-Dubli®
Enfermedades Infecciosas y Microbiología Clínica, 2007
There is a clear need for the development of a rapid and reliable test for the identification of Candida dubliniensis and for the discrimination of this species from Candida albicans. In the present study we have investigated the potential use of C. dubliniensis-specific antigens as a basis for its identification. We produced an anti-C. dubliniensis serum which, after adsorption with C. albicans blastospores, was found to differentially label C. dubliniensis isolates in an indirect immunofluorescence test. In this test, the antiserum reacted with blastospores and germ tubes of C. dubliniensis and with blastospores of Candida krusei and Rhodotorula rubra but did not react with blastospores of several other Candida species including C. albicans. The antiserum also reacted with C. albicans germ tubes. The anti-C. dubliniensis adsorbed serum reacted with specific components of 25, 28, 37, 40, 52, and 62 kDa in the C. dubliniensis extract and with a variety of antigens from other yeast species. The antigens from non-C. dubliniensis yeasts showing reactivity with the anti-C. dubliniensis adsorbed serum are mostly expressed within the cell walls of these yeast species, and this reactivity does not interfere with the use of the anti-C. dubliniensis adsorbed serum in an indirect immunofluorescence test for the rapid identification of C. dubliniensis.
Identification and characterization of nine atypical Candida dubliniensis clinical isolates
Journal of Medical Microbiology, 2014
Candida dubliniensis is a pathogenic yeast of the genus Candida closely related to Candida albicans. The phenotypic similarity of these two species often leads to misidentification of C. dubliniensis isolates in clinical samples. DNA-based methods continue to be the most effective means of discriminating accurately between the two species. Here, we report on the identification of nine unusual Candida isolates that showed ambiguous identification patterns on the basis of their phenotypic and immunological traits. The isolates were categorized into two groups. Group I isolates were unable to produce germ tubes and chlamydospores, and to agglutinate commercial latex particles coated with a mAb highly specific for C. dubliniensis. Group II isolates grew as pink and white colonies on CHROMagar Candida and ChromID Candida, respectively. Carbohydrate assimilation profiles obtained with API/ID32C together with PCR amplification with specific primers and DNA sequencing allowed reliable identification of the nine unusual clinical isolates as C. dubliniensis.
Medical Mycology: Open Access, 2017
Background: Candida albicans, an important pathogen for humans and animals, shares phenotypic features with Candida dubliniensis, leading to misidentification. Thus, the goal of this study was to apply a combination of phenotypic tests for the differentiation of these cryptic species. Methods and findings: Thirty-seven azole-resistant C. albicans from animals and 03 C. dubliniensis from humans were included in this study. Purity of strains was evaluated on CHROMagar Candida™, on which both species present green colonies. Then, phenotypic characterization was performed based on the growth pattern on sunflower seed agar, where C. albicans presents smooth colonies and C. dubliniensis presents rough colonies, and esterase production on Tween 80™ agar, which is positive for C. albicans, forming an opacification zone, and negative for C. dubliniensis. Molecular differentiation was performed with primers CALF/CALR for the amplification of ITS1/ITS2 regions of rDNA, yielding an amplicon of 100 bp for C. albicans, but not for C. dubliniensis. Of the 37 C. albicans, 35 showed green colonies on CHROMagar Candida Medium™, 36 presented smooth colonies on sunflower seed agar, while 34 showed an opacification zone on Tween 80™ agar. PCR yielded 100-bp-amplicons for all 37 C. albicans strains, confirming their identification. Control strains of C. dubliniensis showed the expected phenotypic features and amplicons were not obtained for the specific PCR reaction. Conclusions: The phenotypic methods used were not absolutely effective, however, the combined observation of smooth colonies on sunflower seed agar with an opacification zone on Tween 80™ agar leads to a reliable presumptive phenotypic identification of C. albicans.
BMC Infectious Diseases, 2012
Background: Candida albicans is the most pathogenic Candida species but shares many phenotypic features with Candida dubliniensis and may, therefore, be misidentified in clinical microbiology laboratories. Candidemia cases due to C. dubliniensis are increasingly being reported in recent years. Accurate identification is warranted since mortality rates are highest for C. albicans infections, however, C. dubliniensis has the propensity to develop resistance against azoles more easily. We developed a duplex PCR assay for rapid detection and differentiation of C. albicans from C. dubliniensis for resource-poor settings equipped with basic PCR technology and compared its performance with three phenotypic methods. Methods: Duplex PCR was performed on 122 germ tube positive and 12 germ tube negative isolates of Candida species previously identified by assimilation profiles on Vitek 2 ID-YST system. Typical morphologic characteristics on simplified sunflower seed agar (SSA), and reaction with a commercial (Bichro-Dubli) latex agglutination test were also performed. The assay was further applied on 239 clinical yeast and yeast-like fungi and results were confirmed by DNA sequencing of internal transcribed spacer (ITS) region of rDNA. Results: The results of duplex PCR assay for 122 germ tube positive and 12 germ tube negative isolates of Candida species were comparable to their identification by Vitek 2 ID-YST system, colony characteristics on SSA and latex agglutination test. Application of duplex PCR also correctly identified all 148 C. albicans and 50 C. dubliniensis strains among 239 yeast-like fungi. Conclusions: The data show that both, duplex PCR and Bichro-Dubli are reliable tests for rapid (within few hours) identification of clinical yeast isolates as C. dubliniensis or C. albicans. However, duplex PCR may be applied directly on clinical yeast isolates for their identification as C. dubliniensis or C. albicans as it does not require prior testing for germ tube formation or latex Candida agglutination.
Phenotypic and genotypic characterization of Candida species isolated from candideamia in Iran
Current Medical Mycology, 2018
Background and Purpose: Candidemia is one of the most important fungal infections caused by Candida species. Infections and mortality caused by Candida species have been on a growing trend during the past two decades. The resistance of yeasts to antifungal drugs and their epidemiological issues have highlighted the importance of accurately distinguishing the yeasts at the species level. The technique applied for yeast identification should be fast enough to facilitate the imminent initiation of the appropriate therapy. Candidemia has not been studied comprehensively in Iran yet. Regarding this, the current study aimed to assess the epidemiology of candidemia at Tehran hospitals and compare the results with the previous findings. Materials and Methods: This study was conducted on 204 positive blood cultures obtained from 125 patients hospitalized in several hospitals located in Tehran, Iran, within a period of 13 months. The yeast isolation and species identification were accomplished using several phenotypic methods (i.e., production of germ tube in human serum, culture on CHROMagar Candida, and Corn meal agar containing Tween 80) and molecular methods, such as polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In addition, unknown cases were subjected to PCR sequencing. These methods were then compared in terms of accuracy, sensitivity, and speed of identification. Results: According to the results, C. albicans (62.4%) was the most common isolate, followed by C. parapsilosis (n=36, 17.5%), C. glabrata (n=18, 8.8%), C. tropicalis (n=13, 6.3%), Trichosporon asahii (n=3, 1.5%), C. kefyr (n=2, 1.0%), C. lusitaniae (n=2, 1.0%), C. intermedia (n=1, 0.5%), C. guilliermondii (n=1, 0.5%), and C. krusei (n=1, 0.5%), respectively. Conclusion: As the findings indicated, the most common species causing candidemia were C. albicans, C. parapsilosis, and C. glabrata, respectively. Children less than one year old and people with cancer were at higher risk for candidemia, compared to other groups. Moreover, phenotypic and molecular methods resulted in the identification of 65.2% and 96.6% of the isolates, respectively. Consequently, PCR-RFLP could be concluded as a more favorable technique for species identification.
Candida dubliniensis, a new fungal pathogen
Journal of Basic Microbiology, 2002
There is a high interest in Candida species other than Candida albicans because of the rise and the epidemiological shifts in candidiasis. These emerging Candida species are favored by the increase of immunocompromised patients and new medical practices, and most oropharyngeal candidiasis are observed in HIV-infected patients. Candida dubliniensis is a recently described opportunistic pathogen that is closely related to C. albicans but differs from it with respect to epidemiology, certain virulence characteristics, and the ability to develop fluconazole resistance in vitro. C. dubliniensis has been linked to oral candidiasis in AIDS patients, although it has recently been associated to invasive disease. C. dubliniensis shares diagnostic characteristics with C. albicans, as germ tube-and chlamydospore-production, and it is generally misclassified as C. albicans by standard diagnostic procedures. Several recent studies have attempted to elucidate useful phenotypic and genotypic characteristics for separating both species. A large variety of methods have been developed with the aim of facilitating rapid and accurate identification of this species. These have included differential chromogenic culture media, immunological tests, and enhanced biochemical and enzymatic panels. Chromogenic isolation media, as CHROMagar Candida, demonstrate better detection rates than traditional media, and allow the presumptive identification of C. dubliniensis by means of colony color (dark-green colonies). API 20 C AUX system is considered a reference method, but ID 32 C strip, and the VITEK 2 ID-YST system correctly identify most C. dubliniensis isolates, being the latter the most accurate. Spectroscopic methods, such as Fourier transformed-infrared spectroscopy, offer potential advantages. However, many authors consider that standard methods for differentiation of Candida species are timeconsuming, often insensitive and can fail to distinguish C. dubliniensis. To overcome these drawbacks, molecular tools have been developed to discriminate C. dubliniensis, and particularly those based on the polymerase chain reaction. But, molecular tools prove difficult and too complex for routine use in the clinical laboratory setting and new developments are necessary. Although preliminary studies indicate that most strains of C. dubliniensis are susceptible to antifungal agents, fluconazole-resistant strains have been detected. Furthermore, fluconazole-resistant strains are easily derived in vitro, showing an increased expression of multidrug resistance transporters, as MDR1.