Evaluation of Albicans ID2 and Biggy agar for the isolation and direct identification of vaginal yeast isolates

KDC, Crespilho AM. SENSIBILIDADE DO LAMINOCULTIVO DERMATOBAC® PARA O DIAGNÓSTICO DA ENDOMETRITE FÚNGICA EM ÉGUAS

Resumo Dentre os diferentes fatores etiológicos, a endometrite fúngica representa uma causa frequente de infertilidade na égua. Nesse sentido, dois experimentos foram realizados para avaliar a sensibilidade do Dermatobac®, sistema originalmente desenvolvido para o isolamento de fungos de interesse em Medicina Humana. No Experimento 1, cepas padrão de Candida (n=4) e Aspergyllus (n=1) foram semeadas assepticamente e em duplicata no sistema Dermatobac®, acompanhando-se o crescimento fúngico a cada 24 horas por 7 dias. Para o Experimento 2, foram selecionadas 34 éguas, submetidas à colheita de material uterino para o plaqueamento em Dermatobac® e realização de esfregaços para pesquisa direta de fungos (Controle). No Experimento 1, foi possível a observação macroscópica de todas as cepas de Candida e Aspergyllus a partir de 24 horas do início do cultivo microbiológico. No Experimento 2, foi constatada a presença de leveduras nas lâminas citológicas de cinco animais (14,71%), resultados também confirmados na semeadura em Dermatobac® (sensibilidade de 100%). Foram observados cinco casos falso-positivos caracterizados pelo crescimento microbiológico em sistema Dermatobac® não confirmados através da citologia endometrial, resultados que determinaram a especificidade de 85%. No entanto, todos os casos falso-positivos foram atribuídos a microrganismos contaminantes que apresentaram morfologia diferenciada e tempo de crescimento superior (P<0,05) ao apresentado pelos principais agentes etiológicos das endometrites fúngicas equinas. Conclui-se que o sistema Dermatobac® é eficiente para o diagnóstico macroscópico da endometrite fúngica em equinos, gerando informações visuais a partir de 24 horas de cultivo.

ECM17-dependent methionine/cysteine biosynthesis contributes to biofilm formation in Candida albicans

Candida albicans has become the fourth leading pathogen of nosocomial bloodstream infections largely due to biofilm formation on implanted medical devices. Previous microarray data indicated that almost all genes in methionine (Met)/cysteine (Cys) biosynthesis pathway were up-regulated during biofilm formation, especially during the adherence period. In this work, we studied the role of Met/Cys biosynthesis pathway by disrupting ECM17, a gene encoding sulfite reductase in C. albicans. It was found that the ecm17Δ/Δ mutant failed to catalyze the biochemical reaction from sulfite to H(2)S and hardly grew in media lacking Met and Cys. NaSH, the donor of H(2)S, dose-dependently improved the growth of ecm17Δ/Δ in media lacking a sulfur source. Sufficient Met/Cys supply inhibited the expression of ECM17 in a dose-dependent manner. These results validated the important role of ECM17 in Met/Cys biosynthesis. Interestingly, the ecm17Δ/Δ mutant showed diminished ability to form biofilm, attenuated adhesion on abiotic substrate and decreased filamentation on solid SLD medium, especially under conditions lacking Met/Cys. Further results indicated that ECM17 affected the expressions of ALS3, CSH1, HWP1 and ECE1, and that the cAMP-protein kinase A (PKA) pathway was associated with ECM17 and Met/Cys biosynthesis pathway. These results provide new insights into the role of Met/Cys biosynthesis pathway in regulating cAMP-PKA pathway and benefiting biofilm formation.

Evaluation of fluorescence in situ hybridisation (FISH) for the identification of Candida albicans in comparison with three phenotypic methods

Severe Candida infections are increasing and are associated with considerable morbidity and mortality. Rapid and accurate differentiation of Candida albicans from non-C. albicans species is essential for therapeutic decisions. We therefore developed a fluorescence in situ hybridisation (FISH) assay comprising previously described probes and a newly designed specific C. albicans probe/competitor probe combination. The FISH probes were first evaluated using 99 selected fungal strains covering 31 species, and a specificity between 96% and 100% and a sensitivity of 100%. The FISH assay was then applied to 110 clinical isolates in parallel with API32C, the chromogenic Candida ID agar, and determination of filamentous colony morphology. All tests produced highly reliable results. However, the Candida ID agar misidentified Candida dubliniensis as C. albicans. Determination of filamentous colony morphology allowed 100% reliable identification of C. albicans, but took 48 h. FISH allowed identification of clinical C. albicans isolates within 3 h with a sensitivity and specificity of 100%. FISH was additionally applied to 48 blood cultures showing yeasts in the Gram stain and correctly identified all 33 cases of C. albicans.

Candida albicans or Candida dubliniensis?

Candida albicans is increasing as an opportunistic pathogen causing candidemia and candidiasis worldwide. In addition, other non-albicans Candida species are now also associated with pertinent infections. These include the closely related C. dubliniensis, which shares many phenotypic similarities with C. albicans. These similarities pose problems in the identification of isolates and have previously led to misidentification of these species. As a result, several identification techniques based on phenotypic and genotypic characteristics have been developed to differentiate between these Candida species. This review will focus on the similarities and differences between these two Candida species highlighting different identification methods and their advantages and disadvantages.

Performance of Chromogenic Candida agar and CHROMagar Candida in recovery and presumptive identification of monofungal and polyfungal vaginal isolates

Chromogenic Candida agar (OCCA) is a novel medium facilitating isolation and identification of Candida albicans, C. tropicalis, and C. krusei, as well as indicating polyfungal population in clinical samples. We compare the performance of OCCA, to CHROMagar Candida (CAC) and Sabouraud chloramphenicol agar (SCA). Vaginal swab samples from 392 women were simultaneously inoculated onto three study media. A total of 161 (41.1%) were found to be positive for fungi of which 140 (87%) were monofungal, and 21 (13%) polyfungal. One-hundred and fifty-seven samples (97.5%) were positive on CAC, 156 (96.9%) on OCCA, 148 (91.9%) on SCA and 144 (89.4%) samples were positive on all three media. The yeasts were identified by conventional methods including germ tube test, microscopic morphology on cornmeal-Tween 80 agar, and the commercial API 20C AUX. The 182 isolates were C. albicans (n = 104), C. glabrata (n = 51), C. krusei (n = 7), C. tropicalis (n = 5), C. famata (n = 3), C. kefyr (n = 3), C. zeylanoides (n = 3), C. colliculosa (n = 2), and other species of Candida (n = 4). Among the 21 polyfungal populations, 20 (95.2%) were detected in OCCA, 14 (66.7%) in CAC, and 13 (61.9%) in CAC and OCCA (P <0.05). Most polyfungal populations (47.6%) yielded C. albicans + C. glabrata. The efficiency of both chromogenic media for C. albicans was >or=92.9% at 72 h. OCCA is more efficient and reliable for rapidly identifying C. albicans and polyfungal populations than CAC. However, CAC is more efficient for identifying C. krusei and C. tropicalis. A chromogenic agar with a higher isolation rate of yeasts and better detection of polyfungal populations than SCA, is suggested as a medium of first choice when available.

Evaluation of CHROM-Pal medium for the isolation and direct identification of Candida dubliniensis in primary cultures from the oral cavity

Candida albicans is the species most frequently isolated from oral specimens, but the recovery of other Candida species such as Candida dubliniensis is increasing. Differentiation of C. dubliniensis from C. albicans requires special tests and both species are misidentified in some studies. CHROM-Pal (CH-P) is a novel chromogenic medium used in our laboratory for differentiation between C. albicans and C. dubliniensis on the basis of colony colour and morphology, and chlamydospore production. The performance of CH-P and CHROMagar Candida (CAC) was compared for primary isolation and presumptive identification of yeasts from oral specimens from human immunodeficiency virus (HIV)-infected and uninfected individuals. The identification of Candida species on both media was compared with two reference identification methods (API ID 32 C and multiplex PCR). A total of 137/205 oral swabs (66.8 %) plated onto CH-P and CAC media were positive by culture and resulted in the growth of 171 isolates of Candida species on CH-P, whilst only 159 isolates grew on CAC. C. albicans was the most frequently isolated species in both groups of patients, followed by Candida parapsilosis in the HIV-negative group, and by C. dubliniensis in the HIV-infected group. The other Candida species isolated were Candida guilliermondii, Candida glabrata, Candida krusei, Candida tropicalis, Candida famata, Candida rugosa, Candida kefyr, Candida pelliculosa and Candida pulcherrima. The sensitivity and specificity for identifying C. albicans, C. krusei, C. tropicalis and C. dubliniensis on CH-P were over 98.5 %, always equal to or higher than those obtained when CAC was used. CH-P is a simple reliable medium for primary isolation and presumptive identification of yeast isolates from oral samples. The ability of CH-P to discriminate between C. dubliniensis and C. albicans was significantly higher (P <0.05) than that of CAC.