Evaluation of antifungal susceptibility of dermatophytes of the genus Microsporum / Avaliação da suscetibilidade a antifungicos de dermatofitos do genero Microsporum

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Dermatophytes of the genus Microsporum preferentially invade skin and hair, being M.canis and M.gypseum the most prevalent species in our routine. Topics and systemic antifungal agents are indicated for the treatment of theses dermatophytoses, which is considered more difficult when compared to other genera of keratinofilic fungi. By the way, the determination of in vitro antifungal susceptibility of these organisms is interesting as a guide of empiric therapy, evaluation of therapeutic failures and to evaluate new antifungal agents. However, dermatophytes were not included in the CLSI document (M38-A, 2002). The studies available until now, using fungi conidia, present divergent results due to the lack of standartization and the large number of pre-analytical variables involved. In addiction, once the hyphae forms predominate in infected tissues, there are controversies about if the conidial form would be adequate for the tests. There are few articles in the literature about dynamical evaluation of fungi growth and their growth inhibition rate in contact with antifungal agents, but none with dermatophytes. This study proposed the determination of conditions for broth microdilution susceptibility test and the standardization of dynamical growth evaluation by the BCT® system for six strains of Microsporum sp, determining respectively MIC and MFC and the inhibition rate after application of ciclopirox olamine, terbinafine and griseofulvin. The results pointed: potato dextrose agar as the best culture medium for conidium production, inoculum concentration of 1x 103 conidia/ml, incubation for 7 days at 28ºC and test enpoint at 100% of growth inhibition for broth microdilution test. The MIC results ranged from 1,0 to16,0 µg/ml for ciclopirox olamine, 0,005 to 0,004 µg/ml for terbinafine and 2,5 to 20,0 µg/ml for griseofulvin. On the automatizated system BioCell-Tracer®, the tests were realized with: PLL concentration of 0,05%; inocula of ? 1x106 conídia/ml in 5?l; incubation at 30ºC for 72 to 96hand also 30ºC as the test temperature, 3 hours and 30 minutes as total time of experiment. All strains showed growth inhibition rate above 85% on drug exposure phase against the antifungal agents evaluated, in MIC obtained by both microdilution method and, at least, one dilution below

ASSUNTO(S)

antifungicos dermatophytes dermatofitos antifungal teste de suscetibilidade susceptibility tests

ACESSO AO ARTIGO

Documentos Relacionados