Diferenciação entre Candida albicans e Candida dubliniensis usando caldo Sabouraud hipertônico e ágar Tabaco

INTRODUCTION: Opportunistic fungal infections in immunocompromised hosts are caused by Candida species, and the majority of such infections are due to Candida albicans. However, the emerging pathogen Candida dubliniensis demonstrates several phenotypic characteristics in common with C. albicans, such as production of germ tubes and chlamydospores, calling attention to the development of stable resistance to fluconazole in vitro. The aim of this study was to evaluate the performance of biochemistry identification in the differentiating between C. albicans and C. dubliniensis, by phenotyping of yeast identified as C. albicans. METHODS: Seventy-nine isolates identified as C. albicans by the API system ID 32C were grown on Sabouraud dextrose agar at 30°C for 24-48h and then inoculated on hypertonic Sabouraud broth and tobacco agar. RESULTS: Our results showed that 17 (21.5%) isolates were growth-inhibited on hypertonic Sabouraud broth, a phenotypic trait inconsistent with C. albicans in this medium. However, the results observed on tobacco agar showed that only 9 (11.4%) of the growth-inhibited isolates produced characteristic colonies of C. dubliniensis (rough colonies, yellowish-brown with abundant fragments of hyphae and chlamydospores). CONCLUSIONS: The results suggest that this method is a simple tool for screening C. albicans and non-albicans yeast and for verification of automated identification.INTRODUÇÃO: Infecções fúngicas oportunistas em hospedeiros imunocomprometidos são causadas por espécies de Candida, cuja maioria das infecções se deve a Candida albicans. Entretanto, o patógeno emergente Candida dubliniensis demonstra várias características fenotípicas em comum com C. albicans, tais como produção de tubo germinativo e clamidósporos, solicitando atenção por desenvolver resistência in vitro estável ao fluconazol. O objetivo do presente estudo foi avaliar a performance da identificação bioquímica na diferenciação entre C. albicans e Candida dubliniensis, analisando fenotipicamente leveduras previamente identificadas como C. albicans. MÉTODOS: Setenta e oito isolados identificados como C. albicans pelo sistema API ID 32C foram cultivados em ágar Sabouraud dextrose a 30°C por 24-48h e em seguida inoculados em caldo hipertônico Sabouraud e agar tabaco. RESULTADOS: Nossos resultados mostraram que 17 (21,5%) isolados tiveram o crescimento inibido no caldo hipertônico Sabouraud, característica fenotípica inconsistente para C. albicans neste meio de cultura. Entretanto, os resultados observados em ágar tabaco mostraram que somente 9 (11,4%) dos isolados inibidos produziram colônias características de C. dubliniensis (colônias rugosas, marrom-amarelada com fragmentos de hifas e abundantes clamidósporos). CONCLUSÕES: Os resultados obtidos sugerem que este é um instrumento simples para triagem entre leveduras de C. albicans e não-albicans, bem como confirmação de identificação automatizada

Differentiation between Candida albicans and Candida dubliniensis using hypertonic Sabouraud broth and tobacco agar

INTRODUCTION: Opportunistic fungal infections in immunocompromised hosts are caused by Candida species, and the majority of such infections are due to Candida albicans. However, the emerging pathogen Candida dubliniensis demonstrates several phenotypic characteristics in common with C. albicans, such as production of germ tubes and chlamydospores, calling attention to the development of stable resistance to fluconazole in vitro. The aim of this study was to evaluate the performance of biochemistry identification in the differentiating between C. albicans and C. dubliniensis, by phenotyping of yeast identified as C. albicans. METHODS: Seventy-nine isolates identified as C. albicans by the API system ID 32C were grown on Sabouraud dextrose agar at 30°C for 24-48h and then inoculated on hypertonic Sabouraud broth and tobacco agar. RESULTS: Our results showed that 17 (21.5%) isolates were growth-inhibited on hypertonic Sabouraud broth, a phenotypic trait inconsistent with C. albicans in this medium. However, the results observed on tobacco agar showed that only 9 (11.4%) of the growth-inhibited isolates produced characteristic colonies of C. dubliniensis (rough colonies, yellowish-brown with abundant fragments of hyphae and chlamydospores). CONCLUSIONS: The results suggest that this method is a simple tool for screening C. albicans and non-albicans yeast and for verification of automated identification