ABSTRACT
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.
Subject(s)
Agar , Candida/classification , Culture Media/chemistry , Hypertonic Solutions , Nicotiana , Candida/growth & development , Candida albicans/classification , Candida albicans/growth & development , Humans , Mycological Typing Techniques/methods , Phenotype , Species SpecificityABSTRACT
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.
Subject(s)
Humans , Agar , Candida/classification , Culture Media/chemistry , Hypertonic Solutions , Nicotiana , Candida albicans/classification , Candida albicans/growth & development , Candida/growth & development , Mycological Typing Techniques/methods , Phenotype , Species SpecificityABSTRACT
A criptococose é uma infecção fúngica oportunista causada por leveduras do gênero Cryptococcus, principalmente Cryptococcus neoformans e Cryptococcus gattii. Devido ao tropismo pelo sistema nervoso central, a principal manifestação clínica da doença é a meningite criptocócica, que acomete com maior gravidade indivíduos com síndrome da imunodeficiência adquirida. O interesse em aspectos fenotípicos, tais como diâmetro de cápsula, hidrólise de ureia, atividade fenoloxidase, vem aumentando por constituírem a virulência do fungo. O objetivo do presente estudo foi quimiotipar as espécies de Cryptococcus recuperados de 15 casos de meningite criptocócica, caracterizando-os quanto aos aspectos fenotípicos. Sendo assim, leveduras anteriormente identificadas como C. neoformans (n = 15) pelo sistema semiautomatizado API ID 32C, e armazenadas na micoteca do Laboratório de Micologia da Seção de Bacteriologia e Micologia do Instituto Evandro Chagas, foram quimiotipadas em meio canavanina-glicina-azul de bromotimol, e avaliadas quanto ao crescimento a 37o C, sensibilidade à cicloheximida, hidrólise da ureia e atividade da fenoloxidase. A partir da semeadura em meio canavanina-glicina-azul de bromotimol, observamos que 47 por cento (7/15) das leveduras eram Cryptococcus gattii e 53 por cento (8/15) eram Cryptococcus neoformans. Apenas um isolado (1/15; 6,7 por cento) foi capaz de crescer a 37o C, sendo que todos foram sensíveis à cicloheximida, bem como produziram hidrólise da ureia. A atividade da fenoloxidase foi observada em todos os isolados estudados, ocorrendo em até 72 h após a incubação. Neste estudo, o isolamento de Cryptococcus neoformans em casos de meningite criptocócica em Belém, Estado do Pará, Brasil, foi mais frequente. Tanto Cryptococcus neoformans como Cryptococcus gattii apresentaram características fenotípicas típicas, assumindo-se que em nossa região ocorrem isolados virulentos.
Cryptococcosis is an opportunistic fungal infection that is caused by yeasts of the genus Cryptococcus, mainly Cryptococcus neoformans and Cryptococcus gattii. Due to their tropism for the central nervous system, the main clinical manifestation of the disease is cryptococcal meningitis, which most severely affects individuals with acquired immunodeficiency syndrome. There is increasing interest in some of the phenotypic aspects of these yeasts, such as capsule diameter, urea hydrolysis, and phenoloxidase activity, because they determine the virulence of the fungus. The objective of this study was to determine the chemotype of the Cryptococcus species that were recovered from 15 cases of cryptococcal meningitis and to characterize their phenotypic features. A group of yeasts that were previously identified as C. neoformans (n = 15) by the semi-automated system API ID 32C and stored in the fungal collection of the Laboratory of Mycology of the Bacteriology and Micology Section on the Instituto Evandro Chagas were chemotyped in canavanine glycine bromothymol blue medium and assessed for their growth at 37o C, cycloheximide sensitivity, urea hydrolysis ability, and phenoloxidase activity. Based on culture in canavanine glycine bromothymol blue medium, we observed that 47 per cent (7/15) of the yeasts were C. gattii and that 53 per cent (8/15) were C. neoformans. Only one isolate (1/15) was able to grow at 37o C; all isolates were sensitive to cycloheximide and could hydrolyze urea. Phenoloxidase activity was observed in all groups, occurring up to 72 h after incubation. In this study, cryptococcal meningitis cases in Belém, Pará State, Brazil, were more commonly caused by C. neoformans. Both C. neoformans and C. gattii exhibited typical phenotypic traits, and it was assumed that, virulent isolates occur in our region.
