In vitro activity of voriconazole against dermatophytes, Scopulariopsis brevicaulis and other opportunistic fungi as agents of onychomycosis.

Using a reference microdilution method, we studied the antifungal susceptibility to voriconazole and fluconazole of 304 clinical isolates from four species of onychomycosis-causing dermatophytes, 196 isolates of dermatophytes not related to nail infection as well as Scopulariopsis brevicaulis, Fusarium spp. and Scytalidium dimidiatum. Results showed a high antifungal activity of voriconazole against dermatophytes (geometric mean minimal inhibitory concentration (MIC)=1.14 microg/mL; MIC for 50% of the organisms (MIC(50))=0.062 miccrog/mL; MIC for 90% of the organisms (MIC(90))=0.25 microg/mL). For S. brevicaulis, the in vitro activity of voriconazole was considerably lower (geometric mean MIC=8.52 microg/mL; MIC(50) and MIC(90)=16 microg/mL). Although voriconazole is not among the drugs recommended for the management of onychomycosis, it can be a useful alternative for recalcitrant infections.

[In vitro resistance to fluconazole and itraconazole in clinical isolates of Candida spp and Cryptococcus neoformans]. / Resistencia in vitro al fluconazol e itraconazol en aislamientos clínicos de Candida spp y Cryptococcus neoformans.

An in vitro susceptibility testing of 181 strains of six species of Candida and 21 strains of Cryptococcus neoformans was carried out in order to investigate the resistance to new antifungal drugs. We have studied clinical isolates from 200 different patients of Hospital del Mar (Barcelona) and Hospital La Inmaculada (Almería). An agar diffusion method (NeoSensitabs, Rosco, Taastrup, Denmark), was employed with fluconazole, itraconazole, and reference drugs amphotericin B, flucytosine, tioconazole and ketoconazole. A high level of susceptibility was found for amphotericin B in C. neoformans strains while 19% of them were resistant to flucytosine. All the strains of C. neoformans and Candida guilliermondii were susceptible to the new azoles derivatives and also Candida parapsilosis and Candida albicans had a great susceptibility to this antifungals. A greater level of resistance was found for Candida krusei, Candida tropicalis and Candida glabrata to fluconazole, itraconazole and ketoconazole, but resistance to fluconazole and itraconazole is not always linked because ten resistant strains for fluconazole were susceptible to itraconazole, and two other resistant to itraconazole were susceptible to fluconazole.

Multicenter evaluation of Neo-Sensitabs, a standardized diffusion method for yeast susceptibility testing.

The agar diffusion method Neo-Sensitabs for sensitivity testing, was evaluated with 33 reference strains by fourteen laboratories. Tablets with 5-fluorocytosine, amphotericin B, nystatin, fluconazole, itraconazole, ketoconazole and tioconazole were used on Shadomy modified medium. These tests classify each strain as susceptible, intermediate or resistant to all tested antifungals by measuring the inhibition zone diameters. Intra and interlaboratory reproducibility was studied. Neo-Sensitabs sensitivity for fungi was easy to perform and reliable method with a reproducibility of 97.1% and superior to other commercialized methods, being specially interesting for antifungal susceptibility in vitro testing of triazole derivatives fluconazole and itraconazole.

Biofilm formation by five species of Candida on three clinical materials.

Most recalcitrant infections are associated with colonization and microbial biofilm development. These biofilms are difficult to eliminate by the immune response mechanisms and the current antimicrobial. Fungi can form biofilms on biomaterials commonly used in clinical practice (intravascular catheters, dentures, heart valves, implanted devices, contact lenses and other devices) and are associated with infections. A variety of in vitro models using different substrates/devices have been described. These models have been used to investigate the effect of different variables, including flow, growth time, nutrients and physiological conditions on fungal biofilm formation, morphology and architecture. The purpose of our study is to analyze biofilm formation capacity by 84 strains of Candida spp. (23C. albicans, 23C. parapsilosis, 16C. tropicalis, 17C. glabrata and 5C. krusei) on three materials used in medical devices and its quantification using a method based on viable cell count. Under the conditions of our study, all assayed Candida strains have been able to form biofilms. All species showed greater biofilm formation capacity on Teflon™, with the exception of C. glabrata which displayed higher biofilm formation capacity on PVC. Biofilm formation by Candida spp. varies depending on the type of material on which it grows and on the species and strain of Candida. The method we propose could be of great use to deepen scientific knowledge on this subject of remarkable clinical significance, considering the absence of standard biofilm formation and quantification techniques on the catheters and the level of difficulty associated to those available.

Antifungal activity of posaconazole against Candida spp. and non-Candida clinical yeasts isolates.

The in vitro antifungal activity of posaconazole was tested against 315 yeast clinical isolates and 11 ATCC reference strains by means an agar diffusion method (Neosensitabs, Rosco,Denmark) based in CLSI M44-A2 document. Posaconazole activity was excellent against Cryptococcus and Rhodotorula species studied and showed very good activity against most species of Candida tested. A total of 13 clinical isolates (4.1%) were resistant: Candida albicans (n=5), Candida glabrata (n=5), Candida tropicalis (n=1), Geotrichum australiensis (n=1) and Geotrichum capitatum (n=1). Our results suggest posaconazole is an effective antifungal agent against the most clinically important yeasts species (92.7% of susceptibility). Agar diffusion method provides good conditions for the posaconazole susceptibility study in the routine laboratory.

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.

Diagnostic value of serum antibody and antigen detection in heroin addicts with systemic candidiasis.

The diagnostic value of antibody detection by indirect hemagglutination (IHA), indirect immunofluorescence (IFA), and counterimmunoelectrophoresis (CIE) and of Candida albicans mannan antigen detection by latex agglutination was studied in 36 cases of systemic candidiasis in heroin addicts. The IHA and IFA techniques were highly sensitive (97% and 91%, respectively), but their specificity was low (60% and 50%). When a titer of greater than or equal to 1:2,560 was used as a criterion for IHA positivity, the specificity of the test rose to 87%, with sensitivity at 75%. CIE had a high degree of specificity (96%) but a low degree of sensitivity (58%). A good correlation was found between clinical evolution of infection and serologic data. Two of 12 patients who could be followed for 9-16 months had a rise in antibody titer detected either by IFA or by IHA and CIE. These two patients had a persistent chondrocostal tumor and C. albicans endocarditis, respectively. All of the other patients, who were cured, had a decrease in titer detected by IHA and IFA and had negative CIE results at the end of follow-up. Serum mannan antigen was not found in any case. The detection of antibody to C. albicans may be useful for diagnosis and follow-up of such patients.