Fluconazole and amphotericin-B resistance are associated with increased catalase and superoxide dismutase activity in Candida albicans and Candida dubliniensis

Introduction Candida dubliniensis, a new species of Candida that has been recovered from several sites in healthy people, has been associated with recurrent episodes of oral candidiasis in AIDS and HIV-positive patients. This species is closely related to C. albicans. The enzymatic activity of C. dubliniensis in response to oxidative stress is of interest for the development of drugs to combat C. dubliniensis. Methods Fluconazole- and amphotericin B-resistant strains were generated as described by Fekete-Forgács et al. (2000). Superoxide dismutase (SOD) and catalase assays were performed as described by McCord and Fridovich (1969) and Aebi (1984), respectively. Results We demonstrated that superoxide dismutase (SOD) and catalase activities were significantly higher (p<0.05) in the fluconazole- and amphotericin B-resistant strains of C. dubliniensis and C. albicans than in the sensitive strains. The catalase and SOD activities were also significantly (p<0.01) higher in the sensitive and resistant C. albicans strains than in the respective C. dubliniensis strains. Conclusions These data suggest that C. albicans is better protected from oxidative stress than C. dubliniensis and that fluconazole, like amphotericin B, can induce oxidative stress in Candida; oxidative stress induces an adaptive response that results in a coordinated increase in catalase and SOD activities. .

Candida dubliniensis does not show phospholipase activity: true or false? / Candida dubliniensis não evidencia atividade fosfolipásica: verdadeiro ou falso?

INTRODUCTION: The phospholipase activity in Candida albicans and Candida dubliniensis isolated from oral candidiasis cases were studied. METHODS: The phospholipase activity was evaluated in egg yolk agar. RESULTS: All the C. albicans isolates (n = 48) showed phospholipase activity (mean Pz = 0.66). However, none of the C. dubliniensis isolates (n = 24) showed this activity. CONCLUSIONS: The authors discuss whether these findings are a true characteristic of C. dubliniensis or a consequence of the methodology employed, which includes the possibility that NaCl may have inhibited the enzymatic activity of C. dubliniensis.

INTRODUÇÃO: Avaliou-se a atividade fosfolipásica em Candida albicans e Candida dubliniensis isoladas de casos de candidíase oral. MÉTODOS: A atividade de fosfolipase foi avaliada em ágar gema de ovo. RESULTADOS: Todos os isolados de C. albicans (nº = 48) evidenciaram atividade fosfolipásica (média Pz = 0.66). Todavia, nenhum isolado de C. dubliniensis (nº= 24) demonstrou esta atividade. CONCLUSÕES: Os autores discutem se estes achados são uma característica verdadeira de C. dubliniensis ou uma conseqüência da metodologia empregada, a qual inclui a possibilidade de que o NaCl seja inibidor da atividade enzimática de C. dubliniensis.

Enzymatic and hemolytic activities of Candida dubliniensis strains

Candida dubliniensis is an opportunistic yeast that has been recovered from several body sites in many populations; it is most often recovered from the oral cavities of human immunodeficiency virus-infected patients. Although extensive studies on epidemiology and phylogeny of C. dubliniensis have been performed, little is known about virulence factors such as exoenzymatic and hemolytic activities. In this study we compared proteinase, hyaluronidase, chondroitin sulphatase and hemolytic activities in 18 C. dubliniensis and 30 C. albicans strains isolated from AIDS patients. C. albicans isolates produced higher amounts of proteinase than C. dubliniensis (p < 0.05). All the tested C. dubliniensis strains expressed hyaluronidase and chondroitin sulphatase activities, but none of them were significantly different from those observed with C. albicans (p > 0.05). Hemolytic activity was affected by CaCl2; when this component was absent, we did not notice any significant difference between C. albicans and C. dubliniensis hemolytic activities. On the contrary, when we added 2.5 g percent CaCl2, the hemolytic activity was reduced on C. dubliniensis and stimulated on C. albicans tested strains (p < 0.05).

C. dubliniensis é uma levedura oportunista que, embora já tenha sido isolada de vários sítios anatômicos é, com maior frequência, encontrada na boca de pacientes infectados pelo HIV. Embora tenham sido realizados numerosos estudos sobre a epidemiologia e filogenia, seus fatores de virulência como atividade exoenzimática e atividade hemolítica, são, ainda, pouco conhecidos. Neste estudo comparou-se a atividade in vitro de proteinase, hialuronidase, condroitin sulfatase e atividade hemolítica de 18 cultivos de C. dubliniensis com 30 cultivos de C. albicans, todos isolados de pacientes com SIDA. Foi evidenciada maior atividade de proteinase em C. albicans em relação a C. dubliniensis (p < 0,05). Todos os isolados de C. dubliniensis evidenciaram atividade de hialuronidase e condroitin-sulfatase de forma similar ao observado com C. albicans (p > 0,05). Constatou-se que a atividade hemolítica foi influenciada pelo CaCl2; em sua ausência não foram observadas diferenças na atividade hemolítica das duas espécies; todavia, ao se agregar 2,5 por cento de CaCl2, a atividade hemolítica de C. dubliniensis foi reduzida enquanto a de C. albicans, estimulada (p < 0,05).

Comparison among tomato juice agar with other three media for differentiation of Candida dubliniensis from Candida albicans

O presente estudo teve como objetivo comparar o ágar suco de tomate, um tradicional meio utilizado para observação de ascósporos em leveduras, com o ágar semente de niger, ágar caseína e ágar semente de girassol, na diferenciação fenotípica entre C. albicans e C. dubliniensis. Após 48 h de incubação a 30 ºC, os 26 isolados de C. dublinienis (100%) evidenciaram a formação de clamidoconídios igualmente em todos os meios comparados. Entretanto, quando semeados com C. albicans, a formação de clamidoconídios foi raramente observada, resultando nos seguintes percentuais de ausência destas estruturas: ágar suco de tomate (92,47%), ágar niger (96,7%), ágar caseína (91,39%), ágar semente de girassol (96,7%). Estes resultados permitem-nos sugerir a utilização do ágar suco de tomate como mais um meio que, já no primo-isolamento, é capaz de, presuntivamente, diferenciar C. albicans de C. dubliniensis.

Utilizacão do ágar suco de tomate (ágar V8) na identificacão presuntiva de Candida dubliniensis / Utilization of tomato juice agar (V8 agar) in the presumptive identification of Candida dubliniensis

Avaliou-se a capacidade do ágar suco de tomate (ágar V8) em diferenciar Candida dubliniensis de Candida albicans com base na producão de clamidoconídios. Noventa e três isolados de Candida albicans e vinte e seis de Candida dubliniensis foram incluídos; 100 por cento de Candida dubliniensis formaram clamidoconídios e 92,5 por cento de Candida albicans não evidenciaram estas estruturas. Estes resultados permitem sugerir este meio como recurso alternativo na identificacão presuntiva de Candida dubliniensis.

Different culture media applied to the study of Cryptococcus neoformans susceptibility to amphotericin B and fluconazole

This study compared the performance of three culture media used for the determination of minimal inhibitory concentration (MIC) of amphotericin B and fluconazole against 48 Cryptococcus neoformans strains. For amphotericin B the media employed were RPMI 1640 medium, as indicated by NCCLS as reference, Yeast Nitrogen Base (YNB) as proposed by Ghannoum et al. (YNB-1), Antibiotic medium 3 (AM3) indicated by others, and YNB as proposed by us (YNB-2). In YNB-1, amphotericin B showed broader MIC ranges, varying from 0.125 µg/ml to 1.0 µg/ml; in RPMI 1640 medium and YNB-2 the MICs were similar and in AM3 the MIC ranges were narrower. The same pattern was observed for MIC 90 (per cent). For fluconazole the media employed were RPMI 1640 and YNB-1. The MIC ranges were broader and elevated when YNB-1 was employed. MIC 50 (per cent) were 2.0 µg/ml in RPMI 1640 medium and 4.0 µg/ml in YNB-1. Our results indicate that RPMI 1640 supplemented with (2 per cent) glucose allowed a good growth at 48h; YNB as recommended by Ghannoum et al. provided a broader MIC range, AM3 provided a narrow MIC range for amphotericin B, and YNB-2 was very similar to RPMI 1640 medium.