Performance of Bacticard Candida compared with the germ tube test for the presumptive identification of Candida albicans.

Bacticard Candida was compared with the germ tube test for the rapid, presumptive identification of Candida albicans. This test kit detects the enzymatic activities l-proline aminopeptidase and beta-galactosaminidase in yeast colonies grown on culture media. Candida albicans produces both enzymes whereas other yeasts produce only one or neither of the enzymes. We evaluated 536 isolates including eight genera and 33 species of medically important yeasts, including 228 C. albicans and 36 C. dubliniensis. Both tests did not discriminate between C. albicans and C. dubliniensis isolates. The sensitivity and specificity for the Bacticard Candida test were 97.8 and 96.5%, respectively. Bacticard Candida and germ tube tests detected 246 (93.2%), and 256 (97%) C. albicans plus C. dubliniensis isolates. There were eight false-positive results with BactiCard Candida kit and four false-positive results with the germ tube test. Positive and negative predictive values for Bacticard Candida enzymatic test were 95.3 and 98.4%, respectively, while 97.4 and 98.1% for the germ tube test, its specificity being 98.1% and efficiency 97% (97.7% for germ tube). We have observed slightly lower values of sensitivity and specificity than those reported by others using the BactiCard test kit. Bacticard Candida provides a rapid and accurate alternative to the germ tube test for the presumptive identification of C. albicans.

[Evaluation of a new chromogenic medium (Candida ID) for the isolation and presumptive identification of Candida albicans and other medically important yeasts]. / Evaluación micológica de un nuevo medio de cultivo cromógeno (Candida ID) para el aislamiento e identificación presuntiva de Candida albicans y otras levaduras de interés médico.

Candidiasis is a frequent human infection caused mainly by Candida albicans. However, other species are emerging as important pathogens, as Candida glabrata, Candida parapsilosis, Candida tropicalis, Candida krusei or Candida guilliermondii. Rapid identification of clinical isolates could facilitate diagnosis and treatment. Candida ID (bioMerieux, Spain) is a new medium for the isolation and presumptive identification of yeasts: C. albicans grows as blue colonies, and C. tropicalis, C. guilliermondii, Candida kefyr and Candida lusitaniae as pink ones. The utility of Candida ID was evaluated with more than 700 clinical isolates and type culture collection strains from different genera including Candida, Cryptococcus, Saccharomyces, and Rhodotorula. Presumptive identification was confirmed by germ tube test, microscopic morphology and chlamydoconidia production on corn meal agar and carbohydrate assimilation on API-ATB ID 32C or Vitek (bioMerieux). Growth on Candida ID was rapid (18-24 h) for most of the yeast strains tested. Sensitivity and specificity of identification of C. albicans was significantly high (>98%), since a very low number of isolates were found to be false negative or false positive. A better result was obtained for species growing as pink colonies (>99.5%). Detection of different species of medical important yeasts was easy with Candida ID, as perfectly distinct colors and textures of colonies were observed on this medium. Candida ID allowed the discrimination between C. glabrata (creamy and smooth) and C. krusei (rough and white) colonies. Other species showed different colony textures and colours, white being the predominant colour. Candida ID was very useful for the presumptive identification C. albicans isolates.

[Evaluation of Chromalbicans Agar for presumptive identification of Candida albicans]. / Evaluación del medio Chromalbicans Agar para la identificación presuntiva de Candida albicans.

The utility of Chromalbicans Agar (Biolife Italiana, Milano, Italy) was evaluated with 723 clinical isolates and type culture collection strains from different genera including Candida, Cryptococcus, Pichia, Rhodotorula, Saccharomyces, Trichosporon y Zygosaccharomyces. Presumptive identification was confirmed by germ tube test and carbohydrate assimilation on API-ATB ID 32C (bioMerieux, France). Growth on Chromalbicans Agar was very useful for the presumptive identification of C. albicans isolates, and sensitivity and specificity values were significantly high (>97%), since a very low number of isolates were found to be false negative or false positive.

In vitro susceptibility of Candida dubliniensis to current and new antifungal agents.

BACKGROUND: Candida dubliniensis is a recently described Candida species closely related to Candida albicans, which has been associated with oral candidiasis in HIV-infected patients. Fluconazole-resistant strains of C. dubliniensis are easily obtained in vitro and this fact could be a complication if this resistance develops during treatment with this drug. METHODS: In the present study, the in vitro antifungal susceptibilities of 36 C. dubliniensis clinical isolates and culture strains to current and new antifungal agents, such as amphotericin B (AMB), amphotericin B lipid complex (ABLC), amphotericin B colloidal dispersion (ABCD), 5-fluorocytosine (5FC), fluconazole (FLC), itraconazole (ITC), ketoconazole (KTC), liposomal amphoteri- cin B (LAMB), liposomal nystatin (LNYT), LY303366 (LY), SCH56592 (SCH), and voriconazole (VRC), were determined according to the National Committee for Clinical Laboratory Standards M27-A broth microdilution method for yeasts. RESULTS: Most isolates of C. dubliniensis were susceptible to both new and current antifungal drugs, with 75.9% isolates susceptible to KTC, 86.2% to FLC and to ITC, and approximately 100% to the other antifungal agents tested. The cross-resistance phenotypes are detailed. Four isolates were resistant (MIC > or =64 microg/ml) to FLC. These 4 isolates were also resistant to KTC, and 3 of them were also resistant to ITC (MIC > or =1 microg/ml for both agents). However, these isolates were highly susceptible to 5FC and all polyene formulations (AMB, ABLC, ABCD, LAMB, and LNYT), triazole (SCH and VRC) and echinocandin (LY) antifungal agents. CONCLUSION: The new liposomal and lipidic formulations of AMB, LNYT, and the new triazoles and echinocandins may provide new alternatives to FLC for the treatment of infections by C. dubliniensis.

[Utility of random amplified polymorphic DNA in the discrimination between Candida albicans and Candida dubliniensis]. / Utilidad de la amplificación aleatoria de ADN en la diferenciación de Candida albicans y Candida dubliniensis.

Candida dubliniensisis a recently described species closely related to Candida albicans. Since the discrimination between both species by conventional mycological methods is not easy, many researchers have been trying DNA-related techniques in order to identify C. dubliniensis correctly. In this study, we propose the use of the random amplification of polymorphic DNA (RAPD) with a commercialized short primer which discriminates between both species. This oligonucleotide, AB1-12, allowed also separating C. albicans isolates into four different genotypes. These genotypes were different from the unique genotype observed in C. dubliniensis.

[In vitro activity of a liposomal nystatin formulation (Nyotran) against Cryptococcus neoformans]. / Actividad in vitro de una formulación liposómica de nistatina (Nyotran) frente a Cryptococcus neoformans.

The in vitro antifungal activity of a new liposomal nystatin formulation (NISTL, Nyotran, Aronex Ltd., EE.UU.) was evaluated by a microdilution method with RPMI based on the M27A document of the National Committee for Clinical Laboratory Standards (NCCLS) against 22 isolates of Cryptococcus neoformans. This antifungal activity was compared with those of other seven antifungal agents, such as nystatin (NIST), amphotericin B deoxycholate, liposomal amphotericin B, amphotericin B lipid complex, amphotericin B colloidal dispersion, fluconazole, and itraconazole. NISTL was more active in vitrothan NIST, showing MIC values 2-3 fold smaller in 90% of the isolates. The results obtained suggest that this new formulation would be very helpful for the treatment of cryptococcosis.

[Determination of the in vitro antifungal susceptibility of clinically important yeasts using the Sensititre system]. / Determinación mediante el sistema Sensititre de la sensibilidad in vitro a los antifúngicos de levaduras de interés médico.

Using Sensititre (AccuMed, USA) we studied the in vitro antifungal activity of amphotericin B, fluconazole, itraconazole, ketoconazole and 5-fluorocytosine against 250 clinical yeast isolates taken from different hospitals, including Candida (151 C. albicans, 15 C. krusei, 14 C. parapsilosis, 11 C. tropicalis, 10 C. glabrata, 4 C. guilliermondii, 3 C. rugosa, 2 C. viswanathii, 2 C. famata and 2 C. kefyr), Cryptococcus (32 C. neoformans and 1 C. laurentii), Trichosporon (2 isolates) and Rhodotorula rubra (1 isolate). All the strains were susceptible to amphotericin B and showed an MIC <1 mg/l. The susceptibility of C. albicans (MIC(90) <256 mg/l), C. krusei (MIC(90) <64 mg/l), C. glabrata (MIC(90) <64 mg/l) and C. neoformans (MIC(90) 32 mg/l) to fluconazole was lower (14% isolates being resistant and 16.8% susceptible depending on the dose). The largest number of strains resistant to itraconazole was observed in C. albicans and C. glabrata (17.2% resistant and 24% susceptible and susceptible depending on the dose, respectively). Ketoconazole and 5-fluorocytosine were not effective in vitro against 12.8% and 2%, respectively, of all the isolates studied. Nine C. krusei and seven C. neoformans (12.9%) showed dose-dependent susceptibility to 5-fluorocytosine.