In vitro activity of azole derivatives and griseofulvin against planktonic and biofilm growth of clinical isolates of dermatophytes

Abstract

Background

As shown by recent researches, most of the clinically relevant fungi, including dermatophytes, form biofilms in vitro and in vivo, which may present antimicrobial tolerance favoring recurrent infections.

Objectives

The aim of this study was to determine the minimum inhibitory concentrations (MICs) of itraconazole (ITC), voriconazole (VCZ) and griseofulvin (GRI) against Trichophyton rubrum, Trichophyton tonsurans, Trichophyton mentagrophytes, Microsporum canis and Microsporum gypseum, in planktonic and biofilm growth.

Methods

For the planktonic form, susceptibility testing was performed according to the Clinical and Laboratory Standards Institute (CLSI), document M38-A2, while biofilm susceptibility was evaluated using the XTT colorimetric essay.

Results

The planktonic growth of all strains was inhibited by MIC values ranging from 0.00195-0.1225 μg/mL for VRC, 0.00195-0.25 μg/mL for ITC and <0.0039-4 μg/mL for GRI, while an increase of 50-fold the MIC was required to significantly reduce the metabolic activity (P<0.05) of dermatophyte biofilms.

Conclusions

In brief, the ability of dermatophytes to form biofilms may be a contributing factor for the recalcitrance of dermatophytoses or the dissemination of the disease

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