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

Abstract

As shown by recent research, most of the clinically relevant fungi, including dermatophytes, form biofilms in vitro and in vivo, which may exhibit antimicrobial tolerance that favour recurrent infections. 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. 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. The planktonic growth of all strains was inhibited, with MIC values ranging from 0.00195 to 0.1225 μg/mL for VRC, 0.00195 to 0.25 μg/mL for ITC and <0.0039 to 4 μg/mL for GRI, while a 50-fold increase in the MIC was required to significantly reduce the metabolic activity (P < .05) of dermatophyte biofilms. 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.

2-Hydroxychalcone as a Potent Compound and Photosensitizer Against Dermatophyte Biofilms

“…Some studies conducted by our group have already demonstrated the anti-biofilm activity of chalcones against fungal species such as C. gattii ( Palanco et al., 2017 ) and H. capsulatum ( Melo et al., 2017 ). Studies have been carried out to assess the anti-biofilm action of conventional drugs for treating dermatophytoses such as TRB, FLZ ( Costa-Orlandi et al., 2020 ), itraconazole, voriconazole, griseofulvin ( Brilhante et al., 2018 ), econazole ( Toukabri et al., 2018 ), and formulations of piroctone-based shampoos ( Santos; Dias-Souza, 2017 ). However, in most cases, 50 times the MIC is required to observe any biofilm inhibition ( Brilhante et al., 2018 ).…”

“…Studies have been carried out to assess the anti-biofilm action of conventional drugs for treating dermatophytoses such as TRB, FLZ ( Costa-Orlandi et al., 2020 ), itraconazole, voriconazole, griseofulvin ( Brilhante et al., 2018 ), econazole ( Toukabri et al., 2018 ), and formulations of piroctone-based shampoos ( Santos; Dias-Souza, 2017 ). However, in most cases, 50 times the MIC is required to observe any biofilm inhibition ( Brilhante et al., 2018 ). Planktonic forms (10 6 cells/mL) are more sensitive to drugs when compared to biofilms, confirming that these communities show increased resistance to conventional antifungals.…”

Occurrence of dermatophytosis in dogs from Thrissur, Kerala

“…Prevalence of dermatophytosis was more in dogs and cats (78.7 per cent) than in domestic livestock (33 per cent) in western parts of India (Murmu et al, 2015). In dogs, prevalence of dermatophytosis ranged from four percent to 10 per cent while higher prevalence had been reported in Turkey (Brilhante et al, 2018). Contaminated environment, inanimate objects, animals with subclinical or clinical infections, and animals that were mechanical carriers of the spores on their hair coat acted as reservoirs of infection for both people and animals (Moriello et al, 2017).…”

Immunopathogenesis of Dermatophytoses and Factors Leading to Recalcitrant Infections

“…Although many dermatophyte strains have been shown to form biofilms under experimental conditions and on ex-vivo nail tissue, their existence on the skin in tinea corporis/cruris has not yet been demonstrated. [ 31 ]…”