Oral Yeast Flora and Antibodies to Candida albicans in Homosexual Men: Orale Hefeflora und Antikörper gegen Candida albicans bei homosexuellen Männern

Summary: The oral yeast flora and circulating IgG and IgA antibodies to Candida albicans were investigated in 76 Danish homosexual men C.albicans was isolated from 45 (65%) of 69 subjects by enrichment broth culture, but primary plate cultures were positive in 11 (16%). The frequency of yeast recovery on primary plates increased with decreasing T-lymphocyte helper-to-suppressor ratio (ratio ≤1.0: 33%; 1.1–1.4: 19%; and >1.4: 8%), whereas the frequency of positive enrichment broth cultures did not change (range 64–67%). Demographic or lifestyle parameters did not correlate significantly with oral yeast colonization as did neither IgG nor IgA antibodies to C. albicans. High levels of IgA antibodies to C. albicans were found to be associated with a Th/Ts ratio >1.0 whereas IgG candida antibody levels correlated inversely with the number of sexual partners in the past year. Zusammenfassung: Bei 76 dänischen homosexuellen Männern wurden die orale Hefeflora und IgG- und IgA-Antikörper gegen Candida albicans untersucht. Von 69 Personen konnte C. albicans 45mal (65%) in einem flüssigen Anreicherungsmedium aber nur 11mal (16%) durch primäre Plattenkulturen isoliert werden. Die Häufigkeit des Nachweises auf primären Plattenkulturen steigerte sich mit abnehmender Ratio zwischen Helfer-T-Zellen und Suppressor-T-Zellen (Ratio ≤ 1,0: 33%, 1,1–1,4: 19% und >1,4: 8%). Dagegen war keine Änderung bei den positiven Anreicherungskulturen festzustellen (64 bis 67%). Es zeigten sich keine Korrelationen zwischen der oralen Hefebesiedlung einerseits und demographischen Parametern, der Lebensweise oder der Höhe der IgG- oder IgA-Antikörper gegen C. albicans andererseits. Hohe IgA-Titer gegen C. albicans traten vor allem auf, wenn die Th/Ts-Ratio >1,0 war, während die IgG-AntikörperKonzentrationen zur Anzahl der sexuellen Partner des letzten Jahres vor der Untersuchung umgekehrt proportional waren.     

Experimental systemic virulence of oral Candida dubliniensis isolates in comparison with Candida albicans,Candida tropicalis and Candida krusei

There are no previous studies on the comparative virulence of Candida dubliniensis with other non‐albicans species. The aim of this study was to compare the virulence and infection kinetics of C. dubliniensis and other species. Candida albicans, C. dubliniensis, Candida tropicalis and Candida krusei (reference strains) were inoculated intravenously in mice. For infection kinetics evaluation, a group of five animals were sacrificed after 6 h, 3, 7, 14 and 21 days. Microbiological evaluations (liver, spleen, kidneys, lungs and brain) and histopathological examination of the kidney were performed. The results of virulence evaluation were analysed using Kaplan–Meier survival analysis (5%). Candida dubliniensis‐inoculated mice survived for longer periods compared with those with C. albicans (P = 0.005). No differences were detected in relation to C. tropicalis (P = 0.326) and C. krusei (P = 0.317). Most of the organs were persistently colonised by C. albicans and C. dubliniensis even by day 21. Tendency of C. krusei clearance was observed in all organs. Fungal masses and renal lesions were observed after inoculation of C. albicans, C. dubliniensis and C. tropicalis. Within the limits of the study, data on survival rate and dissemination capacity suggest that C. dubliniensis is less virulent than C. albicans.     

Adherence ability of Candida africana: a comparative study with Candida albicans and Candida dubliniensis

In this study, we compared the adherence ability to human Hela cells and biofilm formation of three closely related Candida yeast. In our experiments, Candida africana showed poor adhesion ability to human Hela cells and the absence of biofilm formation on polyvinyl chloride strips. Conversely, Candida albicans and Candida dubliniensis formed mature biofilms and stable attachment to Hela cells. To our knowledge, this is the first comparative study reporting data on biofilm formation and adherence to human Hela cells by C. africana.     

Differences in patient risk factors and source of candidaemia caused by Candida albicans and Candida glabrata

There is an increasing frequency of candidaemia caused by Candida glabrata which has decreased in vitro susceptibility to fluconazole. Differences in risk factors for candidaemia caused by C. glabrata and C. albicans have not been formally evaluated in a diverse patient group. We performed a retrospective study of adult inpatients from January 1, 2003 to April 30, 2008 with C. glabrata and C. albicans candidaemia at a single tertiary care centre in Detroit, Michigan to evaluate for differences in risk factors and presumed source of infection in these groups. Patients’ underlying conditions, risk factors and source of infection (probable or definite) were compared. Among 119 patients, 80 (67.2%) were C. albicans and 39 (32.8%) C. glabrata. Using logistic regression analysis, patients with C. glabrata infection were more likely to have diabetes mellitus (OR 2.43; 95% CI, 1.06–5.54) and abdominal source of infection (OR 4.53, 95% CI, 1.72–11.92). Mortality rates in the two groups were similar. Patients with C. glabrata candidaemia are more likely to be diabetic and have an abdominal source of infection compared with patients with C. albicans.     

Candida africana and its closest relatives

Candida africana is a recently described opportunistic yeast pathogen that has been linked to vaginal candidiasis. This yeast was first described, in 1995, as atypical chlamydospore‐negative Candida albicans strain, and subsequently proposed as a new Candida species on the basis of morphological, biochemical and physiological characteristics clearly different from those of typical C. albicans isolates. Phylogenetic studies based on the comparison of ribosomal DNA sequences demonstrated that C. africana and C. albicans isolates are too closely related to draw any conclusions regarding the status of a new species. Therefore, on the basis of these studies, some authors considered C. africana as a biovar of C. albicans even if genetic differences may be found if additional regions of genomic DNA are sequenced. The taxonomic situation of C. africana and its phylogenetic relationship with other Candida species is still controversial and remains, at present, a matter of debate. Our goal is to review the current knowledge about C. africana and highlight the development of rapid and accurate tests for its discrimination from C. albicans, Candida dubliniensis and Candida stellatoidea. Furthermore, through the analysis of literature data, we have found that C. africana has a worldwide distribution and a considerable number of features making its study particularly interesting.     

Candida carriage and Candida dubliniensis in oropharyngeal samples of type-1 diabetes mellitus patients

The carriage of Candida dubliniensis in the oral cavities of type-1 diabetic patients were investigated. Of 230 patients 81 (35%) had Candida spp. in their oral cavity; C. albicans was the most frequently isolated species (58%). No C. dubliniensis was found in the study population.     

Initial Candida dubliniensis isolate in Candida spp. positive haemocultures in Turkey between 2001 and 2004

Candida dubliniensis which was first recognized in 1995 can be easily misidentified because of its phenotypic similarities with Candida albicans. In this study blood samples of patients from various departments of Ankara University Medical Faculty between January 2001-June 2004 were investigated for the distribution of Candida spp. and the presence of C. dubliniensis. Culture positive 67 fungi were included to the study. Phenotypic tests such as chlamydospore formation, colony morphology on Staib agar, growth at 45 degrees C, carbohydrate assimilation profiles were investigated for identification and differentiation of C. dubliniensis from C. albicans. To confirm the results polymerase chain reaction were used for suspected C. albicans and C. dubliniensis isolates. Among 38 germ tube and chlamydospore forming isolates, 37 of them were found as C. albicans and one as C. dubliniensis. The incidence of C. dubliniensis in our hospital is still low, this is the first C. dubliniensis isolate as an agent of candidaemia reported from Turkey.     

Four cases of Candida albicans infections with isolates developing pink colonies on CHROMagar Candida plates

Candida albicans, the most commonly isolated yeast species, is typically identified by its green colony-colour on CHROMagar Candida plates. We here report four cases of Candida albicans infections, in which the initial identification was non-albicans isolates due to a clear pink colour of the colonies on CHROMagar Candida plates. However, classical phenotypic criteria, biochemical assimilation pattern and molecular characterisation identified all four isolates as C. albicans isolates.     

Chlamydosporulation of Candida albicans and Candida dubliniensis on mustard agar

Chlamydospores are distinctive morphological forms characteristic of Candida albicans, a phenomenon shared only with the closely related species Candida dubliniensis. The production of chlamydospores has remained an important diagnostic criterion for the differentiation of C. albicans and C. dubliniensis from other yeast. We herein describe a new medium, mustard agar, for chlamydosporulation in Candida. All the strains of C. dubliniensis and C. albicans tested produced chlamydospores on mustard agar, whereas none of the other five species produced chlamydospores.     

Characterization of the Fibrinogen Binding Factor from Candida albicans and Candida tropicalis in Quantitative Immunoelectrophoresis

Summary:  The fibrinogen binding factor (FBF) was characterized in Candida albicans and Candida tropicalis reference systems by crossed immunoaffinoelectrophoresis (CIAE) with free fibrinogen in the first dimension gel. The FBF of Candida albicans and Candida tropicalis showed the same mobility and reactivity and corresponded to a cross reactive glycoproteic antigen. Thus CIAE provides a useful tool for the identification of biologically active antigens.
Zusammenfassung:  Der Fibrinogen-bindende Faktor (FBF) wurde in Candida albicans- und Candida tropicalis -Referenz-systemen mittels gekreuzter Immunoaffinoelektrophorese (CIAE) mit freien Fibrinogen in der ersten Dimension charakterisiert. Die FBF von Candida albicans und Candida tropicalis zeigten die gleiche Motilität und Reaktivität und entsprachen einem kreuzreagierenden Glykoprotein. Die CIAE erweist sich somit als geeignetes Instrument für die Identifizierung biologisch aktiver Antigene.     

Habitats for Candida in medical and hygienic respects

The at present acknowledged 163 species of the genus Candida are living in different habitats. Agents of human candidosis have a comparatively restricted natural distribution, and have been discovered primarily in association with men and animals. Candida albicans holds an exceptional position opposite to the nearly 20 non-C. albicans-species with medical importance. Primary habitat is the digestive tract of men and warm-blooded animals. C. albicans is not ubiquitously distributed in the nature. Carriers of Candida may contaminate their immediate environment with yeasts, but that contamination does not usually spread far. C. albicans survives poorly on dry surfaces, a little bit longer in moist materials. Some non-C. albicans-species have their habitat also in the digestive tracts of men and animals, but different to C. albicans they are also ubiquitously distributed in the surroundings (soil, plants, foods, forages) and are much more resistant to environmental influences. The most important source of Candida species in human diseases is endogenous. The via exogen contamination arising mycoses are involved above all by non-C. albicans-species. The different habitats of the Candida species are decisive for the direct and indirect transmission of yeasts to humans and also for the preventive measures against endogenous and exogenous nosocomial Candida mycoses.     

The involvement of physico-chemical interactions in the adhesion of Candida albicans and Candida dubliniensis to epithelial cells

Candida albicans and Candida dubliniensis are two pathogenic yeasts particularly hazardous to immunocompromised patients. Adhesion of yeast cells to epithelium is considered one of the virulence factors and its study is of major importance. The main aim of this study was the comparison of the influence of physico-chemical properties on the adhesion of C. albicans and C. dubliniensis to epithelium. Two strains of each Candida species were used in the adhesion assays to HeLa cells. Adhered cells were enumerated by direct microscopic images observation. Yeast cell surface tension parameters and degree of hydrophobicity were determined by contact angle measurement. Pseudohyphae and hyphae formation was analysed by scanning electron microscopy. Yeast cells presented no statistical differences concerning their physico-chemical surface properties. However, the extent of adhesion to epithelium was different among the four strains. As general conclusion, yeast adhesion to epithelium seems to be strain-dependent and not directly correlated with pseudohyphae formation.     

Taxonomy and ecology of the genus Candida

Candida is a heterogeneous genus which contains about a quarter of all yeast species. It includes not only species of uncertain affiliation but also unrelated strains whose phylogenetic relationships have not been resolved. A great variety of CoQ types are present in the genus, the mol % G + C ranges from 30-63%, and species that were found to sporulate have teleomorphic counterparts in 11 different genera. Candida species are mainly associated with plants, rotting vegetation, with insects which feed on plants or with food. In line with this, 71% of Candida species utilize xylose (wood degradation), 57% of species use cellobiose (cellulose degradation), 29% oxidize aliphatic hydrocarbons (components of plant cuticula), 27% of species degrade starch as a plant storage material, and 7% utilize methanol as a possible metabolite from pectin catabolism. 85% of species require individual vitamins produced mainly in plant materials. 65% of Candida species are not able to grow at temperatures of 37 degrees C. In comparison only relatively few species occur normally in humans and other warm blooded animals. About 16% of type strains and selected strains for comparative purposes (CBS) were isolated from human specimens. Perhaps up to 10% of Candida species may be of medical importance, though this has so far only been clearly demonstrated for less than 5% of currently known species.     

Influence of serum on in vitro susceptibility testing of echinocandins for Candida parapsilosis and Candida guilliermondii

Echinocandins are antifungal drugs used for the treatment of invasive candidiasis and aspergillosis. They bind to serum proteins within a rate of 96 to >99%. The effect of serum on in vitro echinocandin susceptibility tests of certain Candida and Aspergillus species was reported. This study was performed to determine the effect of human serum on in vitro susceptibility testing of echinocandins for clinical isolates of Candida parapsilosis and Candida guilliermondii, the species which generally have higher minimum inhibitor concentrations compared with other Candida species. One hundred C. parapsilosis and 20 C. guilliermondii isolates were included in the study. The susceptibility tests of caspofungin, micafungin and anidulafungin were performed using microdilution method, either in the presence or absence of 50% human serum, according to the Clinical and Laboratory Standards Institute (CLSI) M27-A3 guidelines. It was demonstrated that human serum significantly affects the in vitro susceptibility results of echinocandins for C. parapsilosis and C. guilliermondii isolates, mostly yielding an increase in MICs. The most prominent fold changes were for micafungin and anidulafungin in C. parapsilosis, and for anidulafungin in C. guilliermondii isolates. Serum influences the in vitro echinocandin susceptibility in C. parapsilosis and C. guilliermondii. The mechanism and clinical significance of this in vitro change need to be clarified.     

Comparison of the susceptibilities of clinical isolates of Candida albicans and Candida dubliniensis to essential oils

Here, a microdilution technique based on the M27-A2 protocol (NCCLS, 2002) was employed to compare the susceptibilities of Candida albicans and Candida dubliniensis to essential oils extracted from plants used as spices. The chemical compositions of the essential oils were defined based on the analysis of retention indices obtained by gas chromatography–mass spectroscopy. Taken together, the results showed that the activity of the compounds against the two species was similar.     

Adherence of Candida albicans and Candida parapsilosis to epithelial cells correlates with fungal cell surface carbohydrates

Many studies have described the adherence of Candida albicans to epithelial cells but little is known about Candida parapsilosis adhesion and its role in host cell surface recognition. This study was designed to evaluate the correlation between the adherence of 20 C. albicans and 12 C. parapsilosis strains to human buccal epithelial cells and the expression of fungal cell surface carbohydrates using lectin histochemistry. Adherence assays were carried out by incubating epithelial cells in yeast suspensions (10⁷ cells ml^?1) and peroxidase conjugated lectins (Con A, WGA, UEA I and PNA at 25 μg ml^?1) were used for lectin histochemistry. The results showed that adherence was overall greater for C. albicans than for C. parapsilosis (P < 0.01) and that the individual strain differences correlated with a high content of cell surface α‐l ‐fucose residues as indicated by the UEA I staining pattern. Based on the saccharide specificity of the lectins used, these results suggest that l ‐fucose residues on cell surface glycoconjugates may represent recognition molecules for interactions between the yeast strain studied and the host (r = 0.6985, P = 0.0045). In addition, our results indicated the presence of α‐d ‐glucose/α‐d ‐mannose, N‐acetyl‐d ‐glucosamine/N‐acetylneuraminic acid and d ‐galactose/N‐acetyl‐d ‐galactosamine in fungal cell wall.     

Evaluation of Mueller-Hinton-agar as a simple medium for the germ tube production of Candida albicans and Candida dubliniensis

Candida albicans is the most frequently isolated yeast species from clinical specimens. A classical rapid presumptive differentiation from non- albicans species is based on its ability to produce germ tubes after incubation in human serum. The only non- albicans Candida species producing germ tubes is Candida dubliniensis. In this study, we evaluated Mueller-Hinton-agar (MH-agar) as a medium for germ tube formation of C. albicans and C. dubliniensis . A total of 859 yeast isolates from stool samples, including 632 strains of C. albicans , 10 C. dubliniensis and 217 other yeast strains from 20 different species, were grown on Sabouraud glucose (2%) agar at 37 °C for 24–72 h. Species were identified by standard methods. For the germ tube test (GTT), an inoculum from a single colony was streaked onto a MH-agar plate and covered by a sterile coverslip. After incubation at 37 °C for 2 h, the MH plates were examined using a light microscope at ×200. The GTT was positive in 578 of 632 C. albicans strains (sensitivity 91.5%), in six of 10 C. dubliniensis strains (sensitivity 60.0%), and in none of the other yeast strains. MH-agar is a suitable medium for the GTT and the presumptive identification of C. albicans . It is safer to use than human serum and is widely available in microbiology laboratories.     

Candida albicans-Serumpräzipitine bei Blutspenderr Auffällige serologische und kulturelle Candida albicans-Befunde bei Alkoholikern

Für serologische Untersuchungen dienten Seren von freiwilligen Blutspendern als Negativkontrolle. Bei 5 von 105 solcher Spender gelang der Nachweis präzipitierender Antikörper (AK) mit Hilfe 2 verschiedener Candida albicans-Antigene, und zwar dem sogenannten Proteolyse-Kulturfiltrat-Antigen und dem herkömmlichen SABOURAUD Dextrose-Kulturfiltrat-Antigen. Die anschließend durchgeführte Untersuchung von Rachenabstrich, Sputum und Stuhl auf C. albicans verlief ebenfalls positiv. Die isolierten C. albicans-Stämme zeigten in Serumalbumin-Agar stärkste Proteolyseaktivität. Bei 4 dieser 5 Blutspender handelte es sich um schwere Alkoholiker. Diese vorläufigen Befunde werden im Hinblick auf die Pathogenese der Candida-Mykosen und die Gesundheitskontrolle des Blutspenders diskutiert.

Summary

Sera from voluntary blood donors served as negative controls in serological studies. In 5 out of 105 donors, precipitating antibody to 2 different C. albicans antigens (so called proteolyzed culture filtrate antigen and conventional S abouraud dextrose culture filtrate antigen) could be demonstrated. Subsequent examination of throat swabs, sputum and stools for yeastlike fungi was also positive. In serum-albumin agar, the C. albicans strains isolated were exhibiting very high proteolytic activity. 4 of the 5 donors involved proved to be severely addicted to alcohol and suffering from latent disease. These preliminary findings are discussed in respect of the pathogenesis of Candida mycoses and health control of blood donors.     

Experimental pathogenicity of Candida albicans and Candida dubliniensis with continuous and discontinuous fringes morphotypes

A possible correlation between the presence of discontinuous fringes and high virulence has been previously suggested. The aim of this study was to compare the pathogenicity of Candida albicans and Candida dubliniensis with continuous and discontinuous fringes morphotypes on mice. For C. albicans, two discontinuous fringe morphotype isolates (PN 69, PN 74), two continuous fringe morphotype isolates (N 60, N 33) and one reference strain were used. For C. dubliniensis, three discontinuous fringe morphotype isolates (97487, 97464, 97519), two continuous fringe morphotype isolates (97040, 98026) and one reference strain were used. Swiss male mice were inoculated with a standardised suspension of the microorganisms and observed for 35 days. The pathogenicity of the isolates was analysed according to parameters proposed previously. Three isolates were considered pathogenic: PN 74, N 60 and 98026. Strain N 60 killed the highest amount of mice (80%). Animals inoculated with C. albicans did not show differences on survival estimate. Candida dubliniensis 98026 was more pathogenic than samples 97464 and 97519. On the other hand, the sample 97487 showed a higher pathogenicity when compared with 97040 (Kaplan–Meier test, P = 0.008). Strains with continuous fringe morphotypes were also associated with Candida sp. virulence in vivo.