In Vitro additive effect on griseofulvin and terbinafine combinations against multidrug-resistant dermatophytes

Griseofulvin (GF) and terbinafine (TF) are commonly used drugs to treat dermatophytosis, a fungal infection of the skin. Today there is an increase in drug resistance to these antifungals which highlight the need for alternative synergistic therapies. Minimum Inhibitory Concentration (MIC) of GF and TF were determined against fungi clinical isolates from local hospitals with values ranging 0.03−2.0 µg mL-1 and 0.24−4.0 µg mL-1, respectively. A checkboard test was used to determine the combination of GF:TF which could induce an additive effect against the fungi isolates Multidrug-resistant isolates showed susceptibility after treatment with 16:2 µg mL-1 GF:TF. An MTT assay further verified that GF and TF combinations have greater additive effect against pathological and multidrug-resistant isolates than antifungals alone. Herein we disclose GF:TF combinations that could constitute as a possible new anti-dermatophyte therapy

Antifungal activity terbinafine, griseofulvin and saponins extracted from Chenopodium quinoa aganst multi-resistant isolates of dermatophytes

As dermatofitoses ou micoses cutâneas são infecções causadas por dermatófitos, fungos que apresentam características morfológicas e fisiológicas especializadas. Apesar dos avanços na terapia antifúngica, a incidência de micoses cutâneas tem aumentado. Entre as várias razões para isso, duas causas merecem destaque: o crescente número de indivíduos imunossuprimidos, e a crescente resistência aos antifúngicos. Além disso, resistência a múltiplos antifúngicos tem se revelado como um sério problema no setor da saúde pública. Assim, este trabalho teve como objetivo avaliar o potencial antifúngico de duas frações purificadas de saponinas de Chenopodium quinoa e analisar o potencial sinérgico in vitro da associação de griseofulvina (GF) e terbinafina (TF) contra 23 isolados de Microsporum canis, M. gypseum, Trichophyton mentagrophytes e T. rubrum. Os testes de susceptibilidade foram realizados segundo a CLSI (M38-A2), seguindo o método de microdiluição. Apesar de já existir relato de saponinas com atividade antifúngica, as duas frações purificadas das saponinas de quinoa testadas, FQ70 e FQ90, não demonstraram efeito inibitório sobre os fungos dermatófitos, mesmo quando combinadas com a GF e a TF. O sinergismo da GF com a TF baseia-se no fato de ambos antifúngicos apresentarem mecanismos de ação diferentes. O teste de susceptibilidade com isolados susceptíveis e resistentes, pelo método do checkerboard, mostrou que em 70% dos casos a combinação apresentou aditividade. Mais ainda, a associação de GF e TF foi capaz de reverter a multirresistência em dois isolados. Os dados do teste com MTT revelaram que o percentual de dano na hifa era maior para a combinação do que o observado com GF e TB isoladamente. A associação também provocou alterações evidentes na morfologia e na composição química do micélio, corroborando com as observações de dano celular in vitro. A análise por DSC e FT-IR indicam a ocorrência de interação molecular entre os dois antifúngicos. A formação de diferentes hábitos cristalinos, observada pela análise por MEV da mistura de ambos fármacos, tende a confirmar essa hipótese, sem descartar o surgimento de formas polimórficas.Dermatophytoses, also called cutaneous mycoses, are infections caused by dermatophytes, fungi that have specialized morphological and physiological characteristics. In despite of the advances in the current antifungal therapy, the incidence of cutaneous mycoses has increased in past years. There are many reasons for this, but two causes deserve attention: the growing number of immunocompromised individuals, and resistance to antifungal agents. Furthermore, resistance to multiple antifungals has been considered as the major problem in the public health sector. This study aimed to evaluate the antifungal potential of two purified fractions of saponins of Chenopodium quinoa and the in vitro potential synergism of griseofulvin (GF) and terbinafine (TF) against 23 isolates dermatophytes of the genera Microsporum canis, M. gypseum Trichophyton mentagrophytes and T. rubrum. Susceptibility tests were performed according to the CLSI Norm M38-A2, following the method of broth microdilution. Though already exists reports about the antifungal activity of saponins, the two saponins of purified factions from quinoa, and FQ70 FQ90, tested showed no inhibitory effect on dermatophyte fungi, even when combined with GF and TF. The synergistic potential GF and TF was postulated considering that both antifungal drugs act by different mechanisms of action. The test of susceptibility in susceptible and resistant isolates by the checkerboard method revealed an additive effect in that 70% of the isolates. Noteworthy, the GF-TF association was able to reverse the multi-drug-resistance in two isolates. In that case, data from the MTT test evidenced that percentage of damage of hyphae induced by the GF-TF association was greater than that observed in monotherapy. Moreover, it also caused significant alterations in the morphology and chemical composition of the mycelium. The analysis of the freeze-dried mixture of GF and FT by DSC and FT-IR allowed the detection of a manifest molecular interaction between the two antifungals. The formation of different crystal habits observed by SEM analysis of the mixture of both drugs tends to endorse this hypothesis, but, without confirming the occurrence of genuine polymorphic forms