In vitro activities of antifungal agents alone and in combination against fluconazole-susceptible and -resistant strains of Candida dubliniensis

In the present study we used two groups of Candida dubliniensis strains: one containing fluconazole-susceptible clinical isolates and another containing fluconazole-resistant laboratory derivative from the former to examine the changes on susceptibility accompanying the development of resistance to fluconazole. Our findings confirmed the ability of C. dubliniensis isolates to become resistant to fluconazole and indicated that this resistance was crossed with ketoconazole, itraconazole, ravuconazole and terbinafine. We also tested combinations of terbinafine, amphotericin B, itraconazole and voriconazole against both groups of isolates in a checkerboard assay. Surprisingly, most combinations evidenced indifferent interactions, and the best synergism appeared when terbinafine and itraconazole were combined against the fluconazole-resistant group.

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.

Reavaliação da suscetibilidade de Candida à anfotericina B: estudo comparativo com isolados de três hospitais do estado do Rio Grande do Sul / Reevaluation of Candida susceptibility to amphotericin B: comparative study using isolates from three hospitals in the state of Rio Grande do Sul

Comparou-se a suscetibilidade à anfotericina B de Candida spp isoladas de candidemias, sendo: 41 do Hospital Universitário de Santa Maria, 56 do Hospital de Clínicas de Porto Alegre e 47 da Santa Casa, Complexo Hospitalar de Porto Alegre. Os testes foram baseados no documento M27-A2 do Clinical Laboratory Standards Institute. Todavia, foram empregadas 20 concentrações de anfotericina B, variáveis entre 0,1 e 2µg/ml. Os testes foram realizados nos meios RPMI 1640 com glicose, antibiotic medium 3 e yeast nitrogen base dextrosado. O caldo antibiotic medium 3 gerou amplas faixas de concentrações inibitórias mínimas e concentrações fungicidas mínimas quando comparado aos demais. As variações de suscetibilidade entre os hospitais foram melhor detectadas no antibiotic médium 3; os isolados do Hospital Universitário de Santa Maria evidenciaram menor sensibilidade do que os da Santa Casa, Complexo Hospitalar de Porto Alegre (p < 0,05). As causas das variações de suscetibilidade não foram avaliadas mas apontam para a necessidade de vigilância da suscetibilidade a anfotericina B.

Susceptibility to amphotericin B was compared between isolates of Candida spp that were obtained from candidemia cases as follows: 41 from Hospital Universitário de Santa Maria, 56 from Hospital de Clínicas, Porto Alegre, and 47 from the Santa Casa hospital complex, Porto Alegre. The tests were based on the document M27-A2 from the Clinical Laboratory Standards Institute, but with 20 concentrations of amphotericin B ranging from 0.1 to 2mg/ml. The tests were carried out using RPMI 1640 medium with glucose, antibiotic medium 3 and yeast nitrogen base-dextrose. The antibiotic medium 3 broth generated wide ranges of minimum inhibitory concentrations and minimum fungicidal concentrations in relation to the other agents. The variations in susceptibility between the hospitals were best detected in antibiotic medium 3. The isolates from Hospital Universitário de Santa Maria showed lower susceptibility than did those from the Santa Casa hospital complex, Porto Alegre (p < 0.05). The causes of the susceptibility variations were not assessed but they indicate the need for surveillance regarding the susceptibility to amphotericin B.

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).