Testes de microdiluição em caldo e diluição em ágar para avaliação da suscetibilidade in vitro de dermatófitos
Data
2007-05-31
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Universidade Federal de Goiás
Resumo
Dermatophytes are keratinophilic fungi that colonize and invade the stratum
corneum of the skin, hair and nails causing the dermatophytosis. An increasing
number of antifungal agents has become available for the treatment of
dermatophytosis, however not all species have the same susceptibility pattern and
may occur relative or absolute resistance of some dermatophytes. The document
M38-A developed by Clinical and Laboratory Standards Institute (CLSI) for
determining the minimal inhibitory concentration (MIC) of different antifungal agents
against filamentous fungi, has not included the dermatophytes. The broth
microdilution method has been evaluated by various researchers, and some
parameters as inoculum size, temperature and duration of incubation and endpoint
determination has been investigated. In this study, the in vitro activity of fluconazole,
itraconazole, ketoconazole, griseofulvin and terbinafine against 60 dermatophyte
isolates, belong to three species, using the broth microdilution technique, with
modifications at temperature and incubation time was used. Additionally, the MIC
values obtained by broth microdilution method were compared with those obtained
by the agar dilution technique. The results obtained by broth microdilution method
showed that all isolates produced clearly detectable growth at 28oC and the MIC
values could be determined after 4 days of incubation for the isolates of Trichophyton
mentagrophytes and 5 days for T. rubrum and Microsporum canis isolates.
Itraconazole, ketoconazole and terbinafine had the lowest MIC values (0.03 μg/ml)
for 33.3%, 31.6% and 15% of the isolates, respectively. A good concordance was
observed between the agar dilution and broth microdilution methods. The levels of
agreement were 91.6% with ketoconazole and griseofulvin, 83.3% with itraconazole,
81.6% with terbinafine and 73.3% with fluconazole for all the tested isolates. In
summary, the results of this study suggest that an incubation time of 5 days and
temperature at 28oC used in broth microdilution and agar dilution methods can
contribute to define and to better interpret the MIC values. Beside, until a reference
method for testing the susceptibilities of dermatophytes is standardized, the similar
results with broth microdilution method become the agar dilution useful for testing the
susceptibility of these fungi.
Descrição
Citação
ARAUJO, Crystiane Rodrigues de. Evaluation of agar dilution and broth microdilution methods for antifungal testing to dermathophytes. 2007. 77 f. Dissertação (Mestrado em Medicina) - Universidade Federal de Goiás, Goiânia, 2007.