Candida africana and its closest relatives (original) (raw)
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Cellular Microbiology
Although Candida species are widespread commensals of the microflora of healthy individuals, they are also among the most important human fungal pathogens that under certain conditions can cause diseases (candidiases) of varying severity ranging from mild superficial infections of the mucous membranes to life-threatening systemic infections. So far, the vast majority of research aimed at understanding the molecular basis of pathogenesis has been focused on the most common species—Candida albicans. Meanwhile, other closely related species belonging to the CTG clade, namely, Candida tropicalis and Candida dubliniensis, are becoming more important in clinical practice, as well as a relatively newly identified species, Candida auris. Despite the close relationship of these microorganisms, it seems that in the course of evolution, they have developed distinct biochemical, metabolic, and physiological adaptations, which they use to fit to commensal niches and achieve full virulence. There...
Candida africana sp. nov., a new human pathogen or a variant of Candida albicans
Mycoses, 2001
Summary. Atypical Candida strains were isolated from patients in Madagascar, Angola and Germany. These isolates were slow growing and were unable to produce chlamydospores. They had atypical carbohydrate assimilation profiles. All strains were unable to assimilate the amino sugars N-acteylglucosamine and glucosamine as well as the disaccharide trehalose and the organic acid dl-lactate. They were germ-tube-positive in serum, but only some of these organisms produced pseudohyphae after a long incubation. As shown by Fourier transform infrared spectroscopy the atypical Candida isolates clustered as a monophyletic group different from C. albicans and C. dubliniensis. All strains belonged to C. albicans serotype B. Considering all data presented here, this group of Candida strains differs from any other known member of the genus Candida. Therefore, it is suggested to represent a new species within the genus Candida for which the name Candida africana is proposed.Zusammenfassung. Atypische Candida-Stämme wurden von Patienten aus Madagaskar, Angola und Deutschland isoliert. Die Keime wuchsen langsam und waren nicht im Stande, Chlamydosporen zu bilden. Allen Stämme fehlte die Eigenschaft, die Aminozucker N-Acetylglucosmin und Glucoasamin, das Disaccharid Trehalose und die organische Säure dl-Laktat zu assimilieren. Im Serum-Keimschlauchtest waren die Isolate positiv, wobei nur einige Stämme nach langer Inkubationszeit Pseudohyphen bilden konnten. Mit Hilfe der Fourier-Transform-Infrarot-Spektroskopie konnte gezeigt werden, daß die atypischen Candida-Stämme bezüglich C. albicans und C. dubliniensis differente Cluster bilden. Alle Stämme gehörten zum C. albicans Serotyp B. Unter Zugrundelegung der hier vorgestellten Ergebnisse unterscheidet sich diese Gruppe von Candida-Stämmen von allen anderen bekannten Vertetern der Gattung Candida. Aus diesem Grund wird vorgeschlagen, hierfür eine neue Spezies einzuführen, die den Namen Candida africana erhalten soll.Zusammenfassung. Atypische Candida-Stämme wurden von Patienten aus Madagaskar, Angola und Deutschland isoliert. Die Keime wuchsen langsam und waren nicht im Stande, Chlamydosporen zu bilden. Allen Stämme fehlte die Eigenschaft, die Aminozucker N-Acetylglucosmin und Glucoasamin, das Disaccharid Trehalose und die organische Säure dl-Laktat zu assimilieren. Im Serum-Keimschlauchtest waren die Isolate positiv, wobei nur einige Stämme nach langer Inkubationszeit Pseudohyphen bilden konnten. Mit Hilfe der Fourier-Transform-Infrarot-Spektroskopie konnte gezeigt werden, daß die atypischen Candida-Stämme bezüglich C. albicans und C. dubliniensis differente Cluster bilden. Alle Stämme gehörten zum C. albicans Serotyp B. Unter Zugrundelegung der hier vorgestellten Ergebnisse unterscheidet sich diese Gruppe von Candida-Stämmen von allen anderen bekannten Vertetern der Gattung Candida. Aus diesem Grund wird vorgeschlagen, hierfür eine neue Spezies einzuführen, die den Namen Candida africana erhalten soll.
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.
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.
Identification of Candida spp. by phenotypic tests and PCR
Brazilian Journal of …, 2010
The correct identification of Candida species is of great importance, as it presents prognostic and therapeutical significance, allowing an early and appropriate antifungical therapy. The purpose of this study was to identify isolates of Candida spp. from oral mucosa of 38 patients with oral candidosis evaluated in 2004 by phenotypic methods and PCR, discriminating C. albicans from the other Candida species. The tests used for phenotypic analysis were germ-tube and chlamydoconidia production, culture in CHROMAgarTMCandida, carbohydrate assimilation test, growth at 45ºC and culture in Tween 80 agar. Genotypic confirmation was performed by PCR. Phenotypic tests showed that 63.2% strains formed germ-tubes, 73.7% produced chlamydoconidia, and 63.2% showed green colonies in chromogenic medium, presumptively indicating C. albicans or C. dubliniensis. The carbohydrate assimilation test confirmed these results. A total of 21% strains were identified as C. krusei and 13.2% were indicative of C. tropicalis. Of these later strains, three produced chlamydoconidia. The association of other phenotypic tests with culture in Tween 80 agar identified 95.8% of strains as C. albicans and 4.2% as C. dubliniensis. All 24 strains indicative of C. albicans and C. dubliniensis were confirmed by PCR as C. albicans.
Revista do Instituto de Medicina Tropical de São Paulo
The aim of this study was to assess a collection of yeasts to verify the presence of Candida dubliniensis among strains isolated from the oral mucosa of AIDS pediatric patients which were initially characterized as Candida albicans by the traditional phenotypic method, as well as to evaluate the main phenotypic methods used in the discrimination between the two species and confirm the identification through genotypic techniques, i.e., DNA sequencing. Twenty-nine samples of C. albicans isolated from this population and kept in a fungi collection were evaluated and re-characterized. In order to differentiate the two species, phenotypic tests (Thermotolerance tests, Chromogenic medium, Staib agar, Tobacco agar, Hypertonic medium) were performed and genotypic techniques using DNA sequencing were employed for confirmation of isolated species. Susceptibility and specificity were calculated for each test. No phenotypic test alone was sufficient to provide definitive identification of C. dubliniensis or C. albicans, as opposed to results of molecular tests. After amplification and sequencing of specific regions of the 29 studied strains, 93.1% of the isolates were identified as C. albicans and 6.9% as C. dubliniensis. The Staib agar assay showed a higher susceptibility (96.3%) in comparison with other phenotypic techniques. Therefore, genotypic methods are indispensable for the conclusive identification and differentiation between these species.
Pathogenicity and virulence of Candida dubliniensis : comparison with C. albicans
Medical Mycology, 2002
Candida dubliniensis is a newly described fungus that is frequently isolated from the oral cavities of HIV-positive patients. Although extensive studies have been performed on the phylogeny of C. dubliniensis, little is known about the pathogenic ecology of this yeast. Here we examined aspects related to C. dubliniensis in comparison with those of C. albicans. When injected intravenously into mice, C. dubliniensis had a higher survival rate than C. albicans. Histopathological analysis disclosed that C. dubliniensis remained mostly in the yeast form in the infected organs, whereas C. albicans changed into the mycelial form. The host inflammatory reaction was aggressive with C. dubliniensis infection and mild with C. albicans infection. Co-culture of the yeasts with human polymorphonuclear leukocytes disclosed that C. dubliniensis is more vulnerable to the fungicidal activity of leukocytes than C. albicans. C. dubliniensis was also more susceptible to the toxic effect of hydrogen peroxide. When cultured in vitro, C. dubliniensis grew more slowly than C. albicans, but the formation of germ tubes was faster. When the fungi were cultured in RPMI 1640, a fetal bovine serum supplement suppressed the growth of C. dubliniensis but enhanced that of C. albicans. These results clearly indicated that C. dubliniensis is less virulence than C. albicans.
Medical Mycology, 2008
Identification of unusual fungal isolates is a major challenge for the clinical laboratory. This report describes the isolation of Candida africana from a patient with vaginitis. This is a doubtful species which possibly represents atypical strains of Candida albicans. Candida africana can be separated morphologically and physiologically from C. albicans but not genetically. The analysis of 26S rRNA gene showed near 100% homology between C. africana and C. albicans.