In vitro activity of voriconazole against dermatophytes, Scopulariopsis brevicaulis and other opportunistic fungi as agents of onychomycosis

Onychomycosis due to Fusarium species in different continents, literature review on diagnosis and treatment

Fusarium species are an emerging cause of onychomycosis, and the number of cases has dramatically increased in recent decades worldwide. This review presents an overview of the onychomycosis cases caused by Fusarium species and diagnosis and treatment that have been reported in the literature. The most common causative agent of onychomycosis is F. solani species complex, which accounts for 11.68% of the cases of Fusarium onychomycosis, followed by the F. oxysporum species complex (164 out of 1669), which is accounted for 9.83% of the total. F. fujikuroi species complex (42 out of 1669) and F. dimerum species complex (7 out of 1669) are responsible for 2.52% and 0.42 cases, respectively. Fusarium nail infections were reported in patients aged range 1-98, accounting for 5.55% (1669 out of 30082) of all cases. Asia has the highest species diversity of Fusarium onychomycosis (31.51%). South America accounts for 21.09%, and the most common causative agent is F. solani (19.32%), followed by F. oxysporum species complex (15.63%). Europe accounts for 4.90% of cases caused by F. oxysporum, followed by F. solani. Africa accounts for 23.87% of the cases due to the F. solani species complex, followed by F. oxysporum and F. fujikuroi. Distal and lateral subungual onychomycosis was the most common clinical symptom accounting for 58.7% (135 out of 230) of the cases. Data analysis relieved that terbinafine and itraconazole are active treatments for Fusarium onychomycosis. For a definitive diagnosis, combining of direct examination, culture and sequencing of the elongation factor of translation 1α are recommended. Accurate identification of the causative agents of onychomycosis due to Fusarium species and antifungal susceptibility testing is essential in patient management.

Dermatophytosis caused by Nannizzia nana (Microsporum nanum): a comprehensive review on a novel pathogen

Keratinophilic fungi are mostly soil-inhabiting organisms with occasional infections in humans and animals. Even though most dermatophytes are host-adapted, cross-species infections are common by zoophilic and geophilic dermatophytes. N. nana is considered an etiological agent of ringworm in pigs but has also been isolated from other animals, including humans. However, it also possesses many characteristics of geophilic dermatophytes including the ability to grow in soil. N. nana produces characteristic pear-shaped macroconidia and usually exhibits an ectothrix pattern of hair infection. It has been isolated from dermatitis lesions as well as from soil. N. nana infections in pigs are not of much concern as far as economy or health is concerned. But it has been associated with onychomycosis and gonathritis in humans, which are significant in human medicine. The shift in the predominance of dermatophytes in humans and the ability to evolve into a potential tinea pathogen necessitates more understanding of the physiology and genetics of N. nana. In this review, we have attempted a detailed analysis of the studies about N. nana, emphasizing growth and cultural characters, physiology, isolation, infection in humans and animals, molecular characterization and antifungal susceptibility.

Antifungal susceptibility testing of dermatophytes: Development and evaluation of an optimised broth microdilution method

BACKGROUND

Dermatophytosis is one of the most common infections affecting 3%-17% of the population. Resistance to antifungals so far was not of concern in the therapeutic management. However, recent reports of terbinafine-resistant strains in several countries are worrisome making antifungal susceptibility testing inevitable.

OBJECTIVES

We aimed to develop and evaluate an optimised broth microdilution assay for antifungal drug susceptibility testing of dermatophytes.

METHODS

We first studied the effect of different inocula, incubation temperatures and incubation times to establish an optimised assay. Subsequently, we tested 79 clinical strains of 11 dermatophyte species with 13 antifungals.

RESULTS

We found inoculating with 0.5-5 × 10⁴ colony forming units (CFU) and incubating at 29°C ± 1°C for 4 days to be appropriate. Terbinafine was the most active antifungal agent with minimum inhibitory concentration (MIC) values ≤ 0.06 µg/mL, expect for one resistant T mentagrophytes strain, which was isolated from an Indian patient. Also, a majority of MICs of other antifungals that are commonly used to treat dermatophytosis were low, except those of fluconazole. Fluconazole MICs do not correlate with the good efficacy in the clinical management.

CONCLUSIONS

Our assay enables fast and reliable susceptibility testing of dermatophytes with a large panel of different antifungals. This helps to improve the therapeutic management of dermatophytosis by detecting resistant strains.

In vitro biofilms and antifungal susceptibility of dermatophyte and non-dermatophyte moulds involved in foot mycosis

Tinea pedis and onychomycosis are among the commonest fungal diseases in the world. Dermatophytes and, less frequently, non-dermatophyte moulds are aetiological agents of foot mycosis and are capable of forming biofilms. Fungal biofilm has demonstrated increasing drug resistance. This work aims to evaluate, in vitro, the ability to form biofilm and the susceptibility to antifungal drugs of sessile dermatophytes and non-dermatophyte moulds involved in foot mycosis. Thirty-six dermatophytes and non-dermatophyte moulds isolated from Tunisian patients with foot mycoses, and identified with MALDI-TOF have been tested. MICs of fluconazole, econazole, itraconazole, terbinafine and griseofulvin were carried out using CLSI broth microdilution method. The ability to form biofilm and antifungal activities of drugs against fungal biofilm formation has been quantified by Crystal Violet and Safranin Red staining. Biomass quantification revealed that all species studied were able to form biofilms in vitro after 72 hours. Fluconazole, econazole, itraconazole and terbinafine inhibited fungal growth with MIC values ranging from 0.031 to >64 μg mL^-1 . The best antifungal activity has been obtained with terbinafine against Fusarium solani. Econazole showed the highest activity against fungal biofilm formation. These findings can help clinicians to develop the appropriate therapy of foot mycosis.

In vitro susceptibilities of Neoscytalidium spp. sequence types to antifungal agents and antimicrobial photodynamic treatment with phenothiazinium photosensitizers

Neoscytalidium spp. are ascomycetous fungi consisting of pigmented and hyaline varieties both able to cause skin and nail infection. Their color-based identification is inaccurate and may compromise the outcome of the studies with these fungi. The aim of this study was to genotype 32 isolates morphologically identified as Neoscytalidiumdimidiatum or N. dimidiatum var. hyalinum by multilocus sequence typing (MLST), differentiate the two varieties by their sequence types, evaluate their susceptibility to seven commercial antifungal drugs [amphotericin B (AMB), voriconazole (VOR), terbinafine (TER), 5-flucytosine (5FC), ketoconazole (KET), fluconazole (FLU), and caspofungin (CAS)], and also to the antimicrobial photodynamic treatment (APDT) with the phenothiazinium photosensitizers (PS) methylene blue (MB), new methylene blue (NMBN), toluidine blue O (TBO) and the pentacyclic derivative S137. The efficacy of each PS was determined, initially, based on its minimal inhibitory concentration (MIC). Additionally, the APDT effects with each PS on the survival of ungerminated and germinated arthroconidia of both varieties were evaluated. Seven loci of Neoscytalidium spp. were sequenced on MLST revealing eight polymorphic sites and six sequence types (ST). All N. dimidiatum var. hyalinum isolates were clustered in a single ST. AMB, VOR and TER were the most effective antifungal agents against both varieties. The hyaline variety isolates were much less tolerant to the azoles than the isolates of the pigmented variety. APDT with S137 showed the lowest MIC for all the isolates of both varieties. APDT with all the PS killed both ungerminated and germinated arthroconidia of both varieties reducing the survival up to 5 logs. Isolates of the hyaline variety were also less tolerant to APDT. APDT with the four PS also increased the plasma membrane permeability of arthroconidia of both varieties but only NMBN and S137 caused peroxidation of the membrane lipids.

Voriconazole-loaded nanostructured lipid carriers (NLC) for drug delivery in deeper regions of the nail plate

Voriconazole-loaded nanostructured lipid carriers (VOR-NLC) were developed and drug penetration evaluated in porcine hooves in vitro. Synergistic effect of urea (Ur), selected among other known chemical enhancers according to hoof hydration potential, was also evaluated. VOR-NLC presented a high encapsulation efficiency (74.52±2.13%), approximate mean diameter of 230nm and were positively charged (+27.32±2.74mV). Stability studies indicated they were stable under refrigeration (4±2°C) for up to 150days. SEM images revealed hooves treated with VOR-NLC and VOR-NLC-Ur suffered a disturbance on the surface depicting high roughness and porosity. Permeation data showed a substantial VOR amount retained in superficial hooves sections independent of the formulation used (2.42±0.26; 2.52±0.36 and 2.41±0.60μg/cm² for unloaded VOR, VOR-NLC and VOR-NLC-Ur, respectively, p>0.05). Still, successive extractions, revealed the amount of VOR retained in deeper regions was significantly higher when VOR-NLC or VOR-NLC-Ur was used (0.17±0.04, 0.47±0.14 and 0.36±0.07μg/cm² for unloaded VOR, VOR-NLC and VOR-NLC-Ur, respectively, p<0.05). Such results indicate NLC are promising formulations for the management of onychomycosis. Further studies in diseased nail plates are necessary.

In Vitro Antifungal Susceptibility Profiles of 12 Antifungal Drugs against 55 Trichophyton schoenleinii Isolates from Tinea Capitis Favosa Patients in Iran, Turkey, and China

Trichophyton schoenleinii is an anthropophilic dermatophyte mainly causing tinea favosa of the scalp in certain regions of the world, especially Africa and Asia. We investigated the in vitro susceptibilities of 55 T. schoenleinii isolates collected over the last 30 years from Iran, Turkey, and China to 12 antifungals using the CLSI broth microdilution method. Our results revealed that terbinafine and ketoconazole were the most potent antifungal agents among those tested, independently of the geographic regions where strains were isolated.

In vitro activities of a wide panel of antifungal drugs against various Scopulariopsis and Microascus species

The in vitro activities of 11 antifungal drugs against 68 Scopulariopsis and Microascus strains were investigated. Amphotericin B, 5-fluorocytosine, fluconazole, itraconazole, ketoconazole, miconazole, posaconazole, voriconazole, and ciclopirox showed no or poor antifungal effect. The best activities were exhibited by terbinafine and caspofungin, where the MIC and MEC (minimal effective concentration) ranges were 0.0313 to >16 μg/ml and 0.125 to 16 μg/ml, respectively. The MIC and MEC modes were both 1 µg/ml for terbinafine and caspofungin; the MIC50 and MEC50 were 1 µg/ml for both drugs, whereas the MIC90 and MEC90 were 4 µg/ml and 16 µg/ml, respectively.

Successful Treatment of Refractory Majocchi's Granuloma with Voriconazole and Review of Published Literature

Majocchi's granuloma (MG) is a rare deep skin dermatophyte infection that can occur either in immunocompetent or in immunocompromised individuals. Oral itraconazole or terbinafine is considered to be the first choice of treatment. We report an immunocompetent man with deep nodular form of MG, the form which is generally found in immunosuppressed individuals. Previous treatment with either oral itraconazole or terbinafine yielded no apparent improvement. After a series of examination, the man was diagnosed as having Trichophyton rubrum-induced MG mixed with bacterial infection as evidenced by growth of Klebsiella pneumoniae in tissue bacterial culture. The patient was treated with a combination of cefoselis and levofloxacin for bacterial clearance followed by voriconazole treatment. After approximately 4 months of voriconazole treatment, the lesions completely resolved. Alternative medicine (voriconazole) can be considered in case of refractory infections during MG treatment.

Comparison of the in vitro activities of newer triazoles and established antifungal agents against Trichophyton rubrum

One hundred eleven clinical Trichophyton rubrum isolates were tested against 7 antifungal agents. The geometric mean MICs of all isolates were, in increasing order: terbinafine, 0.03 mg/liter; voriconazole, 0.05 mg/liter; posaconazole, 0.11 mg/liter; isavuconazole, 0.13 mg/liter; itraconazole, 0.26 mg/liter; griseofulvin, 1.65 mg/liter; and fluconazole, 2.12 mg/liter.

Investigation of In Vitro Activity of Five Antifungal Drugs against Dermatophytes Species Isolated from Clinical Samples Using the E-Test Method

OBJECTIVE

Dermatomycosis is an infection with fungi related to the skin: glabrous skin, hair and/or nails. Oral treatment of fungal infections in dermatology has become a preferred modality for the management of these very common conditions. Although there are increasing numbers of antifungals available for treatment of dermatophytes, some cases and relapses have been unresponsive to treatment. The determination of fungus in-vitro antifungal susceptibility has been reported to be important for the ability to eradicate dermatophytes. It is necessary to perform antifungal susceptibility testing of dermatophytes. E-test (AB Biodisk, Sweden) is a rapid, easy-to-perform in-vitro antifungal susceptibility test. The aim of this study was to investigate the susceptibility of the different species of dermatophyte strains isolated clinical specimens to five antifungal agents using the E-test method.

MATERIALS AND METHODS

A total of 66 specimens were collected from the nails, feet, inguinal region, trunk and hands. These strains tested MIC endpoints of E-test for amphotericin B, fluconazole, itraconazole, caspofungin, and ketoconazole were read after 72, and 96 hours incubation for each strain on RPMI 1640 agar.

RESULTS

The dermatophytes tested included Trichophyton rubrum 43 (65.1%), Trichophyton mentagrophytes 7 (10.7%), Microsporum canis 5 (7.6%), Trichophyton tonsurans 5 (7.6%), Epidermophyton floccosum 4 (6.0%) and Trichophyton violaceum 2 (3.0%). The most active agent against all dermatophytes species was caspofungin with a minimal inhibitory concentration (MIC) range (μg/mL(-1)) (0.02-3, 0.032-4, 0.125-0.50, 0.032-2, 0.25-0.50, 0.125-0.50) and it raconazole with an MIC range (μg/mL(-1)) (0.038-1.5, 0.094-1.5, 1-32, 0.016-0.50, 0.25-0.50, 0.125-0.50). The least active agent was fluconazole with an MIC range (μg/mL(-1)) (0, 19-48, 2-256, 2-8, 256, 256, 8-24).

CONCLUSION

E-test seems to be an alternative method to MIC-determination of antifungal drugs for dermatophytes species, since it is a less-laborious methodology and results could be obtained faster.

Trichophyton tonsurans strains from Brazil: phenotypic heterogeneity, genetic homology, and detection of virulence genes

The objective of this study was to establish the phenotypical and molecular patterns of clinical isolates of Trichophyton tonsurans circulating in the state of Ceará, northeastern Brazil. For this purpose, 25 T. tonsurans strains isolated from independent cases of tinea capitis in children were phenotypically evaluated regarding their macro- and micro-morphological characteristics, vitamin requirements, urease production, and antifungal susceptibility. The molecular characterization was carried out with random amplified polymorphic DNA molecular markers and M13 fingerprinting. The presence of the genes CarbM14, Sub2, CER, URE, ASP, PBL, and LAC, which encode enzymes related to fungal virulence, was also evaluated. Finally, melanin production was assessed through specific staining. The data obtained demonstrated that these T. tonsurans strains have considerable phenotypical variation, although they showed a low degree of genetic polymorphism according to the markers used. The genes CarbM14, Sub2, CER, and URE were detected in all the analyzed strains. The gene LAC was also identified in all the strains, and melanin synthesis was phenotypically confirmed. The strains were susceptible to antifungals, especially itraconazole (GM = 0.06 μg/mL) and ketoconazole (GM = 0.24 μg/mL). Therefore, T. tonsurans strains can present great phenotypical heterogeneity, even in genetically similar isolates. Moreover, the presence of the LAC gene indicates the possible participation of melanin in the pathogenesis of these dermatophytes.

Scopulariopsis, a poorly known opportunistic fungus: spectrum of species in clinical samples and in vitro responses to antifungal drugs

Ninety-nine isolates of clinical origin, tentatively identified as Scopulariopsis or Microascus, were morphologically and molecularly characterized by a combined analysis of the D1/D2 domains of the 28S rRNA gene and a fragment of the elongation factor 1-α gene (EF1-α) sequences. The most prevalent species was Scopulariopsis brevicaulis (49.4%), followed by Scopulariopsis gracilis (14.4%), Scopulariopsis brumptii (7.2%), Microascus cinereus (5.2%), the Scopulariopsis candida species complex (3.1%), and Microascus cirrosus (2.1%). The most common anatomic sites of isolation were the respiratory tract (61.6%), superficial tissue (19.2%), and deep tissue or fluid samples (19.2%). The antifungal susceptibilities of the isolates to eight drugs were tested in vitro, with all the drugs generally showing poor activity.

[New apects in the diagnosis and therapy of dermatomycoses]

Recent observations indicate that Arthroderma benhamiae can cause bullous tinea, that onychomycosis increasingly occurs in children and that molds can cause tinea-like lesions. If a mycotic infection is suspected, the pathogen needs to be identified. The first genetic assays for the detection of dermatophytes have successfully been tested under routine conditions. Using appropriate techniques, genetic diagnosis is faster and more sensitive than a culture. Laboratory standards that would facilitate widespread implementation of genetic identification of dermatophytes have not yet been established. For the identification of yeasts, MALDI-TOF has already been established in many laboratories. This method is being refined for the diagnosis of hyphomycetes too. Newer antimycotics that are approved for certain systemic mycoses such as the triazoles voriconazole and posaconazole and the echinocandines caspofungin, micafungin und anidulafungin may be considered for dermatomycoses that cannot be treated by other therapies. Thermotherapy and photodynamic therapy are additional options in particularly difficult cases.

New therapeutic options for onychomycosis

INTRODUCTION

Onychomycosis is a fungal infection of the nail apparatus that affects 10 - 30% of the global population. Current therapeutic options for onychomycosis have a low to moderate efficacy and result in a 20 - 25% rate of relapse and reinfection. New therapeutic options are needed to broaden the spectrum of treatment options and improve the efficacy of treatment.

AREAS COVERED

This review discusses the emerging pharmacotherapeutics; including topical reformulations of terbinafine, new azole molecules for systemic and topical administration, topical benzoxaboroles and topical polymer barriers. The paper also discusses device-based options, which may be designed to activate a drug or to improve drug delivery, such as photodynamic therapy and iontophoresis; laser device systems have also begun to receive regulatory approval for onychomycosis.

EXPERT OPINION

Device-based therapeutic options for onychomycosis are expanding more rapidly than pharmacotherapy. Systemic azoles are the only class of pharmacotherapy that has shown a comparable efficacy to systemic terbinafine; however terbinafine remains the gold standard. The most notable new topical drugs are tavaborole, efinaconazole and luliconazole, which belong to the benzoxaborole and azole classes of drugs. Photodynamic therapy, iontophoresis and laser therapy have shown positive initial results, but randomized controlled trials are necessary to determine the long-term success of these devices.

Antifungal activity of bis-azasqualenes, inhibitors of oxidosqualene cyclase

The antifungal activity and in vitro toxicity toward animal cells of two inhibitors of oxidosqualene cyclase, squalene bis-diethylamine (SBD) and squalene bis-diethylmethylammonium iodide (SBDI) were studied. Minimum inhibitory concentration (MIC) against dermatophytes and other fungi involved in cutaneous and systemic infections (12 isolates from seven species) were determined by the broth microdilution method based on the reference documents M38-A and M27-A2 of Clinical and Laboratory Standards Institute (CLSI). Both compounds exerted fungistatic activities, although with different action. SBDI was the more active compound and displayed low MIC values (in the 3.12-12.5 μg ml(-1) range) against Microsporum canis, Trichophyton mentagrophytes and one isolate of Scopulariopsis brevicaulis, while SBD showed MIC values against these species in the 3.12-25 μg ml(-1) range. Toxicity was tested on Madin-Darby canine kidney (MDCK) epithelial cells and human microvascular endothelial cells (HMEC). SBDI proved the less toxic compound: it inhibited M. canis, T. mentagrophytes and S. brevicaulis at concentrations below those found toxic for MDCK cells. HMEC were the more sensitive cells.

Scopulariopsis brevicaulis infection of prosthetic valve resembling aspergilloma on histopathology

Fungal prosthetic valve endocarditis is an infrequent but serious complication of valve replacement surgery. Approximately 75% of patients are affected with Candida species. Scopulariopsis species affecting prosthetic valve is rarely reported in the literature.

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.

New triazoles and echinocandins: mode of action, in vitro activity and mechanisms of resistance

Different types of mycoses, especially invasive mycoses caused by yeasts and molds, are a growing problem in healthcare. The most notable explanation for this increase is a rise in the number of immunocompromised patients owing to advances in transplantation, the emergence of AIDS and a rise in the number of invasive surgical procedures. Despite advances in medical practice, some therapeutic problems remain. In addition, intrinsic or acquired antifungal resistance may pose a serious problem to antifungal therapy. A new generation of triazole agents (voriconazole, posaconazole, isavuconazole, ravuconazole and albaconazole) and the recent class of the echinocandins (caspofungin, micafungin and anidulafungin) have become available, and represent an alternative to conventional antifungals for serious fungal infection management. Currently, only two of the recent triazole generation (voriconazole and posaconazole) and all three echinocandins are available for clinical use. More precisely, voriconazole and posaconazole are indicated for the treatment of invasive fungal infections and the echinocandins for the treatment of specific candidiasis. Voriconazole and posaconazole have a very broad spectrum of antifungal activity that includes Candida species, and filamentous and dimorphic fungi. Their activity extends to both fluconazole- and itraconazole-resistant strains of Candida. A major difference between posaconazole and voriconazole is that posaconazole has activity against Zygomycetes including Mucor spp., Rhizopus spp. and Cunninghamella spp., and voriconazole has no activity against this class of fungi. Ravuconazole, isavuconazole and albaconazole have shown very potent in vitro activity against species of Candida, Cryptococcus and Aspergillus, and they are currently in various stages of development. All three echinocandin agents, caspofungin, micafungin and anidulafungin, are similar in their spectrum of activity. Echinocandins do not possess in vitro activity against important basidiomycetes, including Cryptococcus, Rhodotorula and Trichosporon. This review attempts to deliver the most up-to-date knowledge on the mode of action and mechanisms of resistance to triazoles and echinocandins in fungal pathogens. In addition, the in vitro activity data available on triazoles and echinocandins are reported.

[In vitro antifungal activity of voriconazole: New data after the first years of clinical experience]

Voriconazole has been developed to meet the increasing need for new and useful antifungal agents for the treatment of invasive mycoses. This review describes the spectrum of voriconazole antifungal activity based on data from in vitro studies published during the last three years. This survey demonstrates that voriconazole has a broad antifungal spectrum against the most common fungal pathogens being its action fungistatic for Candida and fungicidal for Aspergillus and other filamentous fungi. Overall, more than 95% of all Candida isolates tested are susceptible to voriconazole and less than 3% are resistant. Similar or even better activity rates have been described for Aspergillus, Cryptococcus and most of yeasts and moulds of medical importance. We also discuss the limitations related to the azole cross-resistance observed in some Candida glabrata isolates, the poor activity of voriconazole against Scedosporium prolificans, its activity against fungal biofilms and the great potential usefulness of combination of voriconazole with other antifungal drugs.