Comparison of in vitro activity of five antifungal agents against dermatophytes, using the agar dilution and broth microdilution methods

Abstract

The purpose of this study was to compare the agar dilution and broth microdilution methods for determining the minimum inhibitory concentration (MIC) of fluconazole, itraconazole, ketoconazole, griseofulvin and terbinafine for 60 dermatophyte samples belonging to the species Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum canis. The percentage agreement between the two methods, for all the isolates with < 2 dilutions that were tested was 91.6% for ketoconazole and griseofulvin, 88.3% for itraconazole, 81.6% for terbinafine and 73.3% for fluconazole. One hundred percent agreement was obtained for Trichophyton mentagrophytes isolates evaluated with ketoconazole and griseofulvin. Thus, until a reference method for testing the in vitro susceptibility of dermatophytes is standardized, the similarity of the results between the two methods means that the agar dilution method may be useful for susceptibility testing on these filamentous fungi. Key-words:In vitro susceptibility. Agar dilution. Broth microdilution. Dermatophytes. RESUMOO propósito do presente trabalho foi comparar os métodos de diluição em ágar e diluição em caldo para a determinação de concentração inibitória mínima de fluconazol, itraconazol, cetoconazol, griseofulvina e terbinafina para 60 amostras de dermatófitos pertencentes às espécies, Trichophyton rubrum, Trichophyton. mentagrophytes e Microsporum canis. A porcentagem de acordo entre os dois métodos para todos os isolados testados considerando-se valores < 2 diluições, foram de 91,6% para cetoconazol e para griseofulvina, de 88,3% para itraconazol, de 81,6% para terbinafina e de 73,3% para fluconazol. Uma concordância de 100% foi obtido para isolados de Trichophyton mentagrophytes avaliados com cetoconazol e griseofulvina. Desta forma, até que um método de referência seja padronizado para testar a suscetibilidade in vitro para os dermatófitos, os resultados semelhantes encontrados para os dois métodos fazem com que o método de diluição em ágar possa ser útil no teste de suscetibilidade para estes fungos filamentosos. Palavras-chaves:Suscetibilidade in vitro. Diluição em ágar. Microdiluição em caldo. Dermatófitos.

Population differentiation, antifungal susceptibility, and host range of Trichophyton mentagrophytes isolates causing recalcitrant infections in humans and animals

“…Similarly, recent reports in literature have revealed that the trend of increasing MIC values for terbinafine in the T. mentagrophytes isolates is observed over the years. In the years 2009 to 2012, the MIC 50 for this drug was determined in the range of 0.06–0.125 μg/ml [ 87 – 90 ], and in 2018, this value increased up to 1 μg/ml [ 27 ]. Clinical evidence of relapse and incomplete mycological cure after standard oral terbinafine therapy, i.e.…”

Antifungal drug susceptibility testing of dermatophytes: Laboratory findings to clinical implications

“…[44] But, studies are available comparing disc diffusion with broth microdilution methods. [6061] Niewerth et al , in 1998, compared two methods of antifungal susceptibility testing to test four different species against five topical antifungal agents (griseofulvin, itraconazole, sertaconazole, terbinafine, and ciclopirox olamine) and found discrepancy in the result obtained from these two methods. The agar dilution method yielded higher MIC value than the broth dilution method.…”

Evaluation of Antifungal Effect of Silver Nanoparticles Against Microsporum canis, Trichophyton mentagrophytes and Microsporum gypseum

“…When the control plate was covered completely with fungal growth, the MIC was read. The MIC was determined as the lowest AgNPs and GR concentration that inhibited visible growth (21,22). The experiments were replicated three times.…”