Terbinafine susceptibility patterns for onychomycosis-causative dermatophytes and Scopulariopsis brevicaulis

Antifungals: From Pharmacokinetics to Clinical Practice

The use of antifungal drugs started in the 1950s with polyenes nystatin, natamycin and amphotericin B-deoxycholate (AmB). Until the present day, AmB has been considered to be a hallmark in the treatment of invasive systemic fungal infections. Nevertheless, the success and the use of AmB were associated with severe adverse effects which stimulated the development of new antifungal drugs such as azoles, pyrimidine antimetabolite, mitotic inhibitors, allylamines and echinochandins. However, all of these drugs presented one or more limitations associated with adverse reactions, administration route and more recently the development of resistance. To worsen this scenario, there has been an increase in fungal infections, especially in invasive systemic fungal infections that are particularly difficult to diagnose and treat. In 2022, the World Health Organization (WHO) published the first fungal priority pathogens list, alerting people to the increased incidence of invasive systemic fungal infections and to the associated risk of mortality/morbidity. The report also emphasized the need to rationally use existing drugs and develop new drugs. In this review, we performed an overview of the history of antifungals and their classification, mechanism of action, pharmacokinetic/pharmacodynamic (PK/PD) characteristics and clinical applications. In parallel, we also addressed the contribution of fungi biology and genetics to the development of resistance to antifungal drugs. Considering that drug effectiveness also depends on the mammalian host, we provide an overview on the roles of therapeutic drug monitoring and pharmacogenomics as means to improve the outcome, prevent/reduce antifungal toxicity and prevent the emergence of antifungal resistance. Finally, we present the new antifungals and their main characteristics.

Efficacy of antifungal agents against fungal spores: An in vitro study using microplate laser nephelometry and an artificially infected 3D skin model

Dermal fungal infections seem to have increased over recent years. There is further a shift from anthropophilic dermatophytes to a growing prevalence of zoophilic species and the emergence of resistant strains. New antifungals are needed to combat these fungi and their resting spores. This study aimed to investigate the sporicidal effects of sertaconazole nitrate using microplate laser nephelometry against the microconidia of Trichophyton, chlamydospores of Epidermophyton, blastospores of Candida, and conidia of the mold Scopulariopsis brevicaulis. The results obtained were compared with those from ciclopirox olamine and terbinafine. The sporicidal activity was further determined using infected three-dimensional full skin models to determine the antifungal effects in the presence of human cells. Sertaconazole nitrate inhibited the growth of dermatophytes, molds, and yeasts. Ciclopirox olamine also had good antifungal activity, although higher concentrations were needed compared to sertaconazole nitrate. Terbinafine was highly effective against most dermatophytes, but higher concentrations were required to kill the resistant strain Trichophyton indotineae. Sertaconazole nitrate, ciclopirox olamine, and terbinafine had no negative effects on full skin models. Sertaconazole nitrate reduced the growth of fungal and yeast spores over 72 h. Ciclopirox olamine and terbinafine also inhibited the growth of dermatophytes and molds but had significantly lower effects on the yeast. Sertaconazole nitrate might have advantages over the commonly used antifungals ciclopirox olamine and terbinafine in combating resting spores, which persist in the tissues, and thus in the therapy of recurring dermatomycoses.

Non-dermatophyte fungi in onychomycosis-Epidemiology and consequences for clinical practice

Onychomycoses are difficult-to-treat fungal infections with a high recurrence rate that relates to the anatomic and pathophysiological conditions in the nail organ and the required extended duration of treatment. Clinical-epidemiological studies demonstrated that non-dermatophyte molds and yeasts are the primary causative agents in 20%-30% of onychomycoses. Mixed infections with dermatophytes are observed as well. Therefore, the causative agents should be determined by fungal culture and the antifungal treatment regimen should reliably cover non-dermatophytes, if appropriate. Systemic-topical combination therapy involving a broad-spectrum, locally applied antifungal may increase the mycological and clinical cure rates compared to monotherapy with systemic drugs.

Current knowledge on the etiology and epidemiology of Scopulariopsis infections

Scopulariopsis is a common fungus in the environment, characterized by its intrinsic resistance to the available antifungal drugs. Around 70 cases of infection by this fungus have been described in the literature. Pulmonary and disseminated infections are the most common and their treatment is difficult; therefore, very diverse approaches have been taken, with varied results. A successful outcome has been reported in only a few cases, generally attributed to a multitreatment strategy combining medical and surgical procedures that ultimately led to the resection of the infected tissue if possible, identification of the mould, and an aggressive long-term antifungal therapy. Although most of the infections are caused by Scopulariopsis brevicaulis, a few other species have also been linked to these cases, although molecular evidence has not been proven for all of them. On this basis, more knowledge on the epidemiology, presentation, diagnosis, treatment, and prognosis of these unusual infections would improve their management. This review aims to compile the current data on Scopulariopsis infections.

Anti-fungal potential of ozone against some dermatophytes

Dermatophytes are classified in three genera, Epidermophyton, Microsporum and Trichophyton. They have the capacity to invade keratinized tissue to produce a cutaneous infection known as dermatophytoses. This investigation was performed to study the effect of gaseous ozone and ozonized oil on three specific properties of six different dermatophytes. These properties included sporulation, mycelia leakage of sugar and nutrients and the activity of their hydrolytic enzymes. Generally, ozonized oil was found to be more efficacious than gaseous ozone. Microsporum gypseum and Microsporum canis were the most susceptible, while Trichophyton interdigitale and T. mentagrophytes were relatively resistant. The study revealed a steady decline in spore production of M. gypseum and M. canis on application of ozonated oil. An increase in leakage of electrolytes and sugar was noticed after treatment with ozonized oil in the case of M. gypseum, M. canis, T. interdigitale, T. mentagrophytes and T. rubrum. The results also revealed loss in urease, amylase, alkaline phosphatase, lipase and keratinase enzyme producing capacity of the investigated fungi.

Dermatophytes and other associated fungi in patients attending to some hospitals in Egypt

Dermatophytes are keratinophilic fungi that infect keratinized tissues causing diseases known as dermatophytoses. Dermatophytes are classified in three genera, Epidermophyton, Microsporum, and Trichophyton. This investigation was performed to study the prevalence of dermatomycosis among 640 patients being evaluated at the dermatology clinics at Kasr elainy, El-Husein and Said Galal hospitals in Cairo and Giza between January 2005 and December 2006. The patients were checked for various diseases. Tinea capitis was the most common clinical disease followed by tinea pedis and tinea corporis. Tinea cruris and tinea unguium were the least in occurrence. Tinea versicolor also was detected. The most susceptible persons were children below 10 years followed by those aged 31-40 years. Unicellular yeast was the most common etiological agent and T. tonsuranswas the second most frequent causative agent followed by M. canis.

In Vitro Triple Combination of Antifungal Drugs against Clinical Scopulariopsis and Microascus Species

Broth microdilution checkerboard techniques based on the methodology of the Clinical and Laboratory Standards Institute (CLSI) were employed to study the triple antifungal combination of caspofungin, posaconazole, and terbinafine against 27 clinical isolates of Scopulariopsis and Microascus species. Synergy was observed for 26 isolates, whereas antagonism was observed for Scopulariopsis candida in this study.

Characterization of the antimicrobial susceptibility of fungi responsible for onychomycosis in Spain

Due to the increase of choices relative to antifungals, there is a need to improve the standardization of in vitro methods used to determine the antifungal susceptibility of fungal pathogens. Our study evaluated the in vitro susceptibility of filamentous fungi isolated from patients with toenail onychomycosis against itraconazole, ciclopirox, eberconazole, fluconazole and terbinafine. The minimum inhibitory concentration (MIC) of these antifungal agents was determined with 100 isolates, including dermatophytes (70 strains) and non-dermatophyte molds (30 strains). The susceptibility of fungal isolates was measured by using a technique modified for dermatophytes (0.5 × 10(3)-0.5 × 10(4) conidia/ml as inocula) which followed the procedures described by the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antimicrobial Susceptibility Testing (AFST-EUCAST) and the Clinical and Laboratory Standard Institute (CLSI M38-A). MIC ranges were 0.016-8.0 μg/ml for itraconazole, ciclopirox and eberconazole, 0.063-32.0 μg/ml for fluonazole, and 0.004-2.0 μg/ml for terbinafine. In vitro susceptibility tests indicated that eberconazole has a broad antimicrobial profile, including dermatophytes, as well as other filamentous fungi. Terbinafine was active (0.016-0.250 μg/ml) against dermatophytes.

[Antifungal agents for onychomycoses]

Nail fungal infections are considered one of the major dermatological problems due to their high rate of therapeutic failure, management and treatment difficulties. Long-term treatments, inadequate therapies, mycological misdiagnosis and follow-up, secondary alterations of the nail, and resistant microorganisms, are some of the causes of these complications. Although the discovery of new antifungal agents has provided some effective molecules, none of the current available drugs are totally effective. It is important to continue researching in this field to provide new antifungal agents and combined therapies.