In vitro antifungal oral drug and drug-combination activity against onychomycosis causative dermatophytes

Treatment of onychomycosis in an era of antifungal resistance: Role for antifungal stewardship and topical antifungal agents

A growing body of literature has marked the emergence and spread of antifungal resistance among species of Trichophyton, the most prevalent cause of toenail and fingernail onychomycosis in the United States and Europe. We review published data on rates of oral antifungal resistance among Trichophyton species; causes of antifungal resistance and methods to counteract it; and in vitro data on the role of topical antifungals in the treatment of onychomycosis. Antifungal resistance among species of Trichophyton against terbinafine and itraconazole-the two most common oral treatments for onychomycosis and other superficial fungal infections caused by dermatophytes-has been detected around the globe. Fungal adaptations, patient characteristics (e.g., immunocompromised status; drug-drug interactions), and empirical diagnostic and treatment patterns may contribute to reduced antifungal efficacy and the development of antifungal resistance. Antifungal stewardship efforts aim to ensure proper antifungal use to limit antifungal resistance and improve clinical outcomes. In the treatment of onychomycosis, critical aspects of antifungal stewardship include proper identification of the fungal infection prior to initiation of treatment and improvements in physician and patient education. Topical ciclopirox, efinaconazole and tavaborole, delivered either alone or in combination with oral antifungals, have demonstrated efficacy in vitro against susceptible and/or resistant isolates of Trichophyton species, with low potential for development of antifungal resistance. Additional real-world long-term data are needed to monitor global rates of antifungal resistance and assess the efficacy of oral and topical antifungals, alone or in combination, in counteracting antifungal resistance in the treatment of onychomycosis.

An update on the myriad antifungal resistance mechanisms in dermatophytes and the place of experimental and existential therapeutic agents for Trichophyton complex implicated in tinea corporis and cruris

INTRODUCTION

There is an epidemic emergence of increased resistance in dermatophytes with to antifungal drugs with ergosterol1 (Erg1) and Erg11 mutations to terbinafine and azoles. Apart from mutations, mechanisms that predict clinical failure include efflux pumps, cellular kinases, heat shock proteins (Hsp), and biofilms. Apart from itraconazole and SUBATM (Super-Bioavailable) itraconazole, measures that can be used in terbinafine failure include efflux-pump inhibitors, Hsp inhibitors and judicious use of antifungal drugs (topical + systemic) combinations.

AREAS COVERED

A PubMed search was done for the relevant studies and reviews published in the last 22 years using keywords dermatophytes OR Trichophyton, anti-fungal, resistance, mechanism and fungal AND resistance mechanisms. Our aim was to look for literature on prevalent species and we specifically researched studies on Trichophyton genus. We have analyzed varied antifungal drug mechanisms and detailed varied experimental and approved drugs to treat recalcitrant dermatophytosis.

EXPERT OPINION

Apart from administering drugs with low minimum inhibitory concentration, combinations of oral and topical antifungals (based on synergy data) and new formulations of existing drugs are useful in recalcitrant cases. There is a need for research into resistance mechanism of the existent Trichophyton strains in therapeutic failures in tinea corporis & cruris instead of data derived from laboratory strains which may not mirror clinical failures.

A Carbohydrate-based Synthetic Approach to Diverse Structurally and Stereochemically Complex Chiral Polyheterocycles

Chiral polyheterocycles are one of the most frequently encountered scaffolds in natural products and in current drugs repertoire. A carbohydrate-based diversity oriented synthetic (DOS) approach has been employed for gaining access to many structurally diverse and stereochemically complex rigid polyheterocyclic molecules with multiple chiral hydroxyl groups to enhance aqueous solubility. Inexpensive chiral pool of D-Glucose has been judiciously exploited to get access of complex chiral polyheterocyclic structures using inexpensive, common achiral reagents and domino-Knoevenagel hetero-Diels-Alder (DKHDA) reaction as one of the key synthetic tools. Stereochemistry of newly generated stereocenters of polycyclic structures are unambiguously determined through NMR and X-ray crystallographic study. A chemoinformatic comparison (PCA and PMI) with 40 branded blockbuster drugs showed that newly generated polyheterocycles have good three-dimensional scaffold diversity and most of these pass the Lipinski filter of drug-likeness.

In vitro antifungal combination of terbinafine with itraconazole against isolates of Trichophyton spp

Terbinafine is used as first-line therapy for dermatophytosis, but the incidence of terbinafine-resistance is increasing. Combination of terbinafine with itraconazole was tested by checkerboard based on the EUCAST methodology for antifungal susceptibility testing against 9 terbinafine-susceptible and 7 terbinafine-resistant clinical isolates of Trichophyton spp. from India. Synergistic interactions were observed for 4/9 of the susceptible isolates with fractional inhibitory concentration index (FICI) values of 0.3125 to 0.5 and for 4/7 of the resistant isolates with FICI values of 0.032 to 0.3125.

Antifungal Combinations in Dermatophytes

Dermatophytes are the most common cause of fungal infections worldwide, affecting millions of people annually. The emergence of resistance among dermatophytes along with the availability of antifungal susceptibility procedures suitable for testing antifungal agents against this group of fungi make the combinatorial approach particularly interesting to be investigated. Therefore, we reviewed the scientific literature concerning the antifungal combinations against dermatophytes. A literature search on the subject performed in PubMed yielded 68 publications: 37 articles referring to in vitro studies and 31 articles referring to case reports or clinical studies. In vitro studies involved over 400 clinical isolates of dermatophytes (69% Trichophyton spp., 29% Microsporum spp., and 2% Epidermophyton floccosum). Combinations included two antifungal agents or an antifungal agent plus another chemical compound including plant extracts or essential oils, calcineurin inhibitors, peptides, disinfectant agents, and others. In general, drug combinations yielded variable results spanning from synergism to indifference. Antagonism was rarely seen. In over 700 patients with documented dermatophyte infections, an antifungal combination approach could be evaluated. The most frequent combination included a systemic antifungal agent administered orally (i.e., terbinafine, griseofulvin, or azole-mainly itraconazole) plus a topical medication (i.e., azole, terbinafine, ciclopirox, amorolfine) for several weeks. Clinical results indicate that association of antifungal agents is effective, and it might be useful to accelerate the clinical and microbiological healing of a superficial infection. Antifungal combinations in dermatophytes have gained considerable scientific interest over the years and, in consideration of the interesting results available so far, it is desirable to continue the research in this field.

Checkerboard Analysis To Evaluate Synergistic Combinations of Existing Antifungal Drugs and Propylene Glycol Monocaprylate in Isolates from Recalcitrant Tinea Corporis and Cruris Patients Harboring Squalene Epoxidase Gene Mutation

Recalcitrant dermatophytic infections of the glabrous skin (tinea corporis/cruris/faciei) pose a huge challenge to health care systems. Combinations of oral and topical drugs may potentially improve cure rates, but the same has never been objectively assessed for this condition in laboratory or clinical studies. The present study was undertaken with the aim of identifying synergistic combinations of oral and topical antifungals by testing clinical isolates obtained from patients with recalcitrant tinea corporis/cruris. Forty-two patients with tinea corporis/cruris who had failed oral antifungals or had relapsed within 4 weeks of apparent clinical cure were recruited. Twenty-one isolates were identified by sequencing (all belonging to the Trichophyton mentagrophytes/T. interdigitale species complex) and subjected to antifungal susceptibility testing (AFST) and squalene epoxidase (SQLE) gene mutation analysis. Finally, five isolates, four with underlying SQLE gene mutations and one wild-type strain, were chosen for checkerboard studies using various combinations of antifungal agents. Most isolates (n = 16) showed high MICs of terbinafine (TRB) (0.5 to >16 μg/ml), with SQLE gene mutations being present in all isolates with MICs of ≥0.5 μg/ml. Synergistic interactions were noted with combinations of itraconazole with luliconazole, TRB, and ketoconazole and propylene glycol monocaprylate (PGMC) with luliconazole and with the triple combination of PGMC with luliconazole and ketoconazole. In vitro synergistic interactions provide a sound scientific basis for the possible clinical use of antifungal combinations. Hence, these synergistic combinations may be tested for clinical utility in the wake of rising resistance among dermatophytic infections of the glabrous skin.

The effects of secreted aspartyl proteinase inhibitor ritonavir on azoles-resistant strains of Candida albicans as well as regulatory role of SAP2 and ERG11

BACKGROUND

Candida albicans, the main human fungal pathogen, can cause fungal infection and seriously affect people's health and life. This study aimed to investigate the effects of ritonavir (RIT) on C. albicans and the correlation between SAP2 as well as ERG11 and drug resistance.

RESULTS

Secreted aspartyl proteinases (Saps) activities and pathogenicity of C. albicans with different drug resistance were measured. M27-A4 broth microdilution method was used to analyze the drug sensitivity of RIT combined with fluconazole (FCA) on C. albicans. After that, SAP2 and ERG11 mutations were examined by polymerase chain reaction (PCR) and sequencing, and quantitative real-time PCR was utilized to determine the expression of the two genes. By analyzing pz values, the Saps activity of cross-resistant strains was the highest, followed by voriconazole (VRC)-resistant strains, FCA-resistant strains, itraconazole (ITR)-resistant strains, and sensitive strains. The pathogenicity of C. albicans in descending order was as follows: cross-resistant strains, VRC-resistant strains, ITR-resistant strains, FCA-resistant strains, and sensitive strains. With the increase of RIT concentrations, the Saps activity was gradually inhibited. Drug sensitivity results showed that there was no synergistic effect between RIT and FCA. Additionally, no gene mutation sites were found in SAP2 sequencing, and 17 synonymous mutations and 6 missense mutations occurred in ERG11 sequencing. Finally, the expression of SAP2 and ERG11 was significantly higher in the resistant strains compared with the sensitive strains, and there was a positive liner correlation between SAP2 and ERG11 messenger RNA expression (r = .6655, p < .001).

CONCLUSION

These findings may help to improve our understanding of azole-resistant mechanisms of C. albicans and provide a novel direction for clinical therapeutics of C. albicans infection.

Evaluation of activity and toxicity of combining clioquinol with ciclopirox and terbinafine in alternative models of dermatophytosis

Dermatophytosis is a superficial fungal infection that affects humans and is very common in small animals. The treatment using the most commonly used antifungals is failing, and new therapeutic alternatives are required to combat the resistance of these fungal infections. Previous studies by the group have shown that clioquinol is an important therapeutic alternative in the treatment of dermatophytosis. The object was to conduct studies of antidermatophytic activity and the irritant potential from the double and triple combinations of clioquinol, terbinafine and ciclopirox in ex vivo and in vivo alternative models. To evaluate the irritant potential of antifungal combinations, the alternative HET-CAM method (chicken egg test chorioallantoic membrane) was used. Ex vivo models were used to assess the effectiveness of antifungal combinations, using pig hooves and veterinary fur. Any possible tissue damage was to assess through in histopathology of swine ears. HET-CAM results showed that all combinations can be classified as non-irritating, corroborated by the results of the histopathological evaluation of the pig's ear skin. Only the double combinations managed to remove 100% of the colony-forming units (CFU) formed on the pig's hooves. The clioquinol + terbinafine combination and the triple combination were more effective than clioquinol + ciclopirox in eradicating the preformed biofilm in fur of veterinary origin. These results show the potential of formulations of clioquinol in combination with antifungals for use in humans and in the veterinary field to combat dermatophytosis, as an important alternative therapy, for use in the near future.

In Vitro Combination Effect of Topical and Oral Anti-Onychomycosis Drugs on Trichophyton rubrum and Trichophyton interdigitale

To evaluate the combination effects of anti-onychomycosis drugs, the minimum inhibitory concentrations of topical (efinaconazole, luliconazole, and tavaborole) and oral (itraconazole and terbinafine) drugs for Trichophyton rubrum and Trichophyton interdigitale (8 each, with a total of 16 strains) were determined using the microdilution checkerboard technique based on the Clinical and Laboratory Standard Institute guidelines. No antagonism was observed between the topical and oral drugs against all the tested strains. Efinaconazole with terbinafine exerted a synergistic effect on 43.8% of the strains tested (7/16 strains) and efinaconazole with itraconazole on 12.5% (2/16 strains). Conversely, luliconazole showed no synergistic effect with terbinafine but was synergistically effective with itraconazole against 31.3% of the strains (5/16 strains). Tavaborole showed no synergistic effect with terbinafine and was synergistically effective with itraconazole against 18.8% of the strains (3/16 strains). The results suggest that a combination of topical and oral drugs could be a potential clinical option for onychomycosis treatment, and overall, the efinaconazole and oral drug combination would be the most advantageous among the tested combinations.

Aspirin and verapamil increase the sensitivity of Candida albicans to caspofungin under planktonic and biofilm conditions

OBJECTIVES

This study aimed to investigate the effects of caspofungin (CAS) combined with aspirin (ASP) or verapamil (VPL) on the sensitivity of Candida albicans under planktonic and biofilm conditions.

METHODS

A total of 39 C. albicans clinical strains were used to construct biofilms. Sensitivity to ASP or VPL combined with CAS was analysed by broth microdilution. MIC₅₀ values were obtained and the fractional inhibitory concentration index (FICI) was calculated. Subsequently, C. albicans ZY22 was selected for time-growth curve analysis and strains ZY15 and ZY22 were used for time-kill curve analysis.

RESULTS

Under planktonic condition the MIC₅₀ of CAS was 0.0313-8 μg/mL following treatment with CAS alone, whereas it decreased to 0.0313-4 μg/mL following CAS combined with ASP or VPL. Under biofilm condition the MIC₅₀ of CAS was 0.125-16 μg/mL following treatment with CAS alone, whereas it decreased to 0.0625-16 μg/mL or 0.0625-8 μg/mL following CAS combined with ASP or VPL. FICI results showed synergistic interactions between CAS and ASP under planktonic and biofilm conditions in 17 and 16 strains, respectively. However, synergistic interactions between CAS and VPL under planktonic and biofilm conditions were observed in 19 and 23 strains, respectively. Additionally, 8000 μg/mL ASP or 8 μg/mL VPL combined with CAS had better inhibitory effects on C. albicans.

CONCLUSION

ASP and VPL may be a sensitiser for CAS, and the antifungal effects of CAS may be sensitised by 8000 μg/mL ASP or 8 μg/mL VPL against C. albicans under planktonic and biofilm conditions.

Antifungal activity of phytotherapeutic preparation of Baccharis species from argentine Puna against clinically relevant fungi

ETHNOPHARMACOLOGICAL RELEVANCE

B. boliviensis and B. tola are used in traditional medicine in the Argentine Puna to treat skin and soft tissue infections and inflammatory processes in humans and animals.

AIM OF THE STUDY

To assess the potential of phytotherapeutic preparations of Baccharis species as antifungal agents against clinically relevant fungi and to determine the chemical composition of the extracts.

MATERIAL AND METHODS

Phytotherapeutic preparations of B. boliviensis and B. tola collected in Argentine Puna were evaluated as an antifungal agent against clinically relevant fungi (yeast, non-dermatophytes, and dermatophytes) isolated of patients from a local Hospital, and reference strains, using macrodilution and microdilution assays. The bioactivity was supported by UHPLC-OT-MS metabolome fingerprinting.

RESULTS

The results revealed that the plant preparations were active against most of evaluated fungal strains; B. boliviensis was more active than B. tola. Dermatophyte fungi strains were the most sensitive isolates. The phytotherapeutic preparation showed Minimal Inhibitory Concentration (MIC) values between 25 and 400 μg GAE/mL and Minimum Fungicidal Concentration (MFC) values between 50 and 400 μg GAE/mL. Regarding the phytochemical analysis, total phenolic and total flavonoid contents of hydroalcoholic preparation of B. boliviensis were greater than those of the B. tola extract. Both Baccharis species showed similar chromatographic patterns, fifty-two compounds were identified based on UHPLC-OT-MS including several terpenoids, flavonoids and phenolic acids that have been identified in this two endemic South American Baccharis species for the first time. Several identified compounds present antifungal properties, the presence of these compounds support the bioactivity of the Baccharis extracts.

CONCLUSIONS

In this work the traditional use of both Baccharis species as an antimicrobial against commercial products resistant fungal strains was validate, principally against dermatophytes fungi such as T. rubrum, T. mentagrophytes, M. canis, and M. gypseum. These results indicate that the hydroalcoholic preparations could be used for the treatment of fungal infectious.

The Tetrazole VT-1161 Is a Potent Inhibitor of Trichophyton rubrum through Its Inhibition of T. rubrum CYP51

Prior to characterization of antifungal inhibitors that target CYP51, Trichophyton rubrum CYP51 was expressed in Escherichia coli, purified, and characterized. T. rubrum CYP51 bound lanosterol, obtusifoliol, and eburicol with similar affinities (dissociation constant [K_d ] values, 22.7, 20.3, and 20.9 μM, respectively) but displayed substrate specificity, insofar as only eburicol was demethylated in CYP51 reconstitution assays (turnover number, 1.55 min^-1; K_m value, 2 μM). The investigational agent VT-1161 bound tightly to T. rubrum CYP51 (K_d = 242 nM) with an affinity similar to that of clotrimazole, fluconazole, ketoconazole, and voriconazole (K_d values, 179, 173, 312, and 304 nM, respectively) and with an affinity lower than that of itraconazole (K_d = 53 nM). Determinations of 50% inhibitory concentrations (IC₅₀s) using 0.5 μM CYP51 showed that VT-1161 was a tight-binding inhibitor of T. rubrum CYP51 activity, yielding an IC₅₀ of 0.14 μM, whereas itraconazole, fluconazole, and ketoconazole had IC₅₀s of 0.26, 0.4, and 0.6 μM, respectively. When the activity of VT-1161 was tested against 34 clinical isolates, VT-1161 was a potent inhibitor of T. rubrum growth, with MIC₅₀, MIC₉₀, and geometric mean MIC values of ≤0.03, 0.06, and 0.033 μg ml^-1, respectively. With its selectivity versus human CYP51 and drug-metabolizing cytochrome P450s having already been established, VT-1161 should prove to be safe and effective in combating T. rubrum infections in patients.

In vitro activity of new azoles luliconazole and lanoconazole compared with ten other antifungal drugs against clinical dermatophyte isolates

In vitro susceptibilities of 100 clinical dermatophyte isolates belonging to five species from Iran toward lanoconazole and luliconazole were compared with ten other antifungal agents including econazole, itraconazole, miconazole, fluconazole, griseofulvin, butenafine, terbinafine, caspofungin, anidulafungin and tolnaftate. MIC and MEC values were analyzed according to CLSI M38-A2 document. The isolates were previously identified to the species level using PCR-RFLP on ITS rDNA region. The range of luliconazole and lanoconazole minimum inhibitory concentrations (MICs) was 0.016-0.032 and 0.063-1 μg/ml, respectively for dermatophyte species. Luliconazole and lanoconazole revealed potent activity against all dermatophyte isolates. Anidulafungin, caspofungin, and luliconazole showed the best activity with the lowest geometric mean 0.01, 0.016, and 0.018 μg/ml, respectively, followed by tolnaftate (0.06 μg/ml), terbinafine (0.07 μg/ml), itraconazole (0.183 μg/ml), butenafine (0.188 μg/ml), econazole (0.20 μg/ml), lanoconazole (0.24 μg/ml), griseofulvin (1.28 μg/ml), miconazole (2.34 μg/ml) and fluconazole (15.34 μg/ml). The current study demonstrated luliconazole and lanoconazole displayed excellent activity against all dermatophyte isolates, although the majority of dermatophyte isolates showed low susceptibility to griseofulvin and very low to miconazole, and fluconazole.

Trichophyton rubrum is inhibited by free and nanoparticle encapsulated curcumin by induction of nitrosative stress after photodynamic activation

Antimicrobial photodynamic inhibition (aPI) utilizes radical stress generated from the excitation of a photosensitizer (PS) with light to destroy pathogens. Its use against Trichophyton rubrum, a dermatophytic fungus with increasing incidence and resistance, has not been well characterized. Our aim was to evaluate the mechanism of action of aPI against T. rubrum using curcumin as the PS in both free and nanoparticle (curc-np) form. Nanocarriers stabilize curcumin and allow for enhanced solubility and PS delivery. Curcumin aPI, at optimal conditions of 10 μg/mL of PS with 10 J/cm² of blue light (417 ± 5 nm), completely inhibited fungal growth (p<0.0001) via induction of reactive oxygen (ROS) and nitrogen species (RNS), which was associated with fungal death by apoptosis. Interestingly, only scavengers of RNS impeded aPI efficacy, suggesting that curcumin acts potently via a nitrosative pathway. The curc-np induced greater NO^• expression and enhanced apoptosis of fungal cells, highlighting curc-np aPI as a potential treatment for T. rubrum skin infections.

In vitro susceptibility of dermatomycoses agents to six antifungal drugs and evaluation by fractional inhibitory concentration index of combined effects of amorolfine and itraconazole in dermatophytes

To investigate the antifungal drug susceptibility of fungi responsible for dermatomycoses, minimum inhibition concentration (MIC) tests were performed in 44 strains of dermatophytes, including Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton verrucosum, Trichophyton tonsurans, Microsporum canis, Microsporum gypseum and Epidermophyton floccosum, with six antifungal drugs (amorolfine, terbinafine, butenafine, ketoconazole, itraconazole and bifonazole) by broth microdilution assay according to Clinical Laboratory Standard Institute protocols. Six possible dermatomycosis-causing non-dermatophytic fungi were also tested. The two major causes of tinea, T. rubrum and T. mentagrophytes, showed significantly different sensitivities to ketoconazole and bifonazole. Clinically derived dermatophytes were sensitive to the six antifungal drugs tested. However, non-dermatophytes, especially Fusarium spp., tended to be resistant to these antifungal drugs. In Trichophyton spp., the MICs of non-azole drugs had narrower distributions than those of azoles. To evaluate the effects of antifungal drug combinations, the fractional inhibitory concentration index was calculated for the combination of amorolfine and itraconazole as representative external and internal drugs for dermatophytes. It was found that this combination had synergistic or additive effects on most dermatophytes, and had no antagonistic effects. The variation in susceptibility of clinically derived fungal isolates indicates that identification of causative fungi is indispensable for appropriately choosing effective antifungal drugs in the early stages of infection. The results of combination assay suggest that multiple drugs with different antifungal mechanisms against growth of dermatophytes should be used to treat refractory dermatomycoses, especially onychomycosis.

Onychomycosis caused by Scopulariopsis brevicaulis: report of two cases

Onychomycosis is usually caused by dermatophytes, but some nondermatophytic molds and yeasts are also associated with invasion of nails. Scopulariopsis brevicaulis is a nondermatophytic mold found in soil as a saprophyte. We report two cases of onychomycosis caused by S. brevicaulis in a 48-year-old male and a 79-year-old female. The two patients presented with a typical distal and lateral subungual onychomycosis. Direct microscopic examination of the potassium hydroxide preparation revealed fungal elements. From toenail lesions of the patients, brown colonies with powdery surface, which are a characteristic of S. brevicaulis, were cultured on two Sabouraud's dextrose agar plates. Three cultures taken from nail plates within a 2-week interval yielded similar findings. Numerous branched conidiophores with chains of rough walled, lemon-shaped conidia were observed in slide culture by light microscopy and scanning electron microscopy. The nucleotide sequences of the internal transcribed spacer for the two clinical isolates were identical to that of S. brevicaulis strain WM 04.498. To date, a total of 13 cases of S. brevicaulis onychomycosis including the two present cases have been reported in Korea. Mean age of the patients was 46.1 years, with a higher prevalence in males (69.2%). Toenail involvement was observed in all cases including a case involving both fingernail and toenail. The most frequent clinical presentation was distal and lateral subungual onychomycosis in 12 cases, while one case was proximal subungual onychomycosis.

An update on treatment of onychomycosis

Onychomycosis (OM) is a fungal infection of the nail plate or nail bed which is highly prevalent in the general population and also responsible for significant morbidity. The condition needs to be treated in view of the physical and emotional handicap it produces. The peculiarities of the nail apparatus in health and disease lead to difficulties in being able to successfully treat this condition. Hence, the very same antifungals which produce high cure rates in skin infections are rendered less efficacious in nail disease. Low cure rates and high relapse rates even with highly efficacious antifungals have lead to an increasing interest in exploring newer treatment options which can ensure drug penetration, drug persistence, mycological cure and effective prevention of relapse. The current review aims to summarize our current status of knowledge about the treatment options for OM. It also summarizes the newer areas of research especially with respect to devices related therapies; physical measures to enhance penetration through nail; and development and evaluation of synergistic combinations.

The susceptibility of dermatophytes to photodynamic treatment with special focus on Trichophyton rubrum

Owing to the accessibility of skin to light, many applications of photodynamic treatment (PDT) have been developed within dermatology. The recent increase of dermatological antimicrobial PDT investigations is related to the growing problem of bacterial and fungal resistance to antibiotics. This review focuses on the susceptibility of dermatophytic fungi, in particular Trichophyton rubrum, to PDT and shows its potential usefulness in treatment of clinical dermatophytoses. There are no data indicating significant differences in PDT susceptibility between various dermatophytes and it is unlikely that treatment problems of especially T. rubrum with current antimycotics would occur in case of PDT. Red light 5-aminolevulinic acid-mediated PDT is after repeated sessions successful in in vivo treatment of onychomycosis (fungal nail infection) caused by various dermatophytes. Regarding skin dermatophytoses, UVA-1 PDT with cationic porphyrins appears to be safe and efficient. Most effective toward T. rubrum ex vivo is 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) when combined with UVA-1 radiation or red light; this creates the possibility of efficiently treating nail infections and remaining spores in hair follicles. If the promising in vitro and ex vivo results could be transferred to clinical practice, then PDT has a good prospect to become a worthy alternative to established antifungal drugs.

Comparison of the activities of four antifungal agents in an in vitro model of dermatophyte nail infection

Background:

Onychomycosis is a difficult condition to treat and cure rates are disappointing. Moreover fungicidal action of antifungal agents in NCCLS assays and their rapid accumulation in nails in vivo are not compatible with the duration of treatment.

Aims:

This study aimed to find the effectiveness of 4 different antifungal agents in an in vitro model with some similarities to in vivo conditions.

Materials and Methods:

Strains of Trichophyton rubrum I-III, Trichophyton mentagrophytes (usual form), Trichophyton mentagrophytes 73, Epidermophyton Flucosom, Microsporum Canis, and Trichophyton Schoenleini which were isolated from the nails of patients, were hired. Inocula suspensions were prepared from 7 to 14 day-old cultures of dermatophytes. Antifungal agents including fluconazole, ketoconazole, terbinafine, and griseofulvin were obtained as standard powders. For each antifungal agent, initial MIC was calculated by registering the optical density for 10 two-fold serially diluted forms which was incubated with diluted fungal suspensions with RPMI 1640. Human nail powder inoculated with different strains and incubated in RPMI 1640 and different concentrations of antifungal drugs for 4 weeks. Final MIC at different steps of 1, 2, 3 and 4 weeks were investigated.

Results:

The final MIC that resulted from the incubation of dermatophytes with nail powder was much more than the initial which was concluded from conventional MIC assay. Terbinafine had the lowest rate of initial and final MICs.

Conclusion:

The model described here may present more similar conditions to clinical fungal infections; therefore the results such as MIC may be more helpful for hiring the most effective antifungal agent.

Trichophyton rubrum and Trichophyton interdigitale: genetic diversity among species and strains by random amplified polymorphic DNA method

Onychomycosis is a common condition that represents up to 50% of all nail problems and 30% of all cases of dermatophytoses. Trichophyton rubrum and Trichophyton interdigitale are the most common agents involved in this condition. In cases of recurrent post-treatment onychomycosis, strain fingerprinting could reveal whether the original isolate is responsible, a new strain has been acquired or if multiple strains are involved. The aim of this study was to evaluate the efficacy of the RAPD method for species and strain differentiation of T. rubrum and T. interdigitale obtained from patients with subungeal distal-lateral onychomycosis. A set of 86 strains of onychomycosis causative dermatophytes were submitted to species differentiation and strain typing by RAPD method with two previously described primers. Both primers proved capable of strain differentiation when tested for each species. Nineteen molecular profiles were configured for T. rubrum isolates with primers 1 and 6. For T. mentagrophytes, ten molecular profiles were configured with primer 1 and twenty-one with primer 6. We found that T. interdigitale and T. rubrum species were grouped in different clusters when both primers were analyzed together. This study shows that these primers are valuable tools for strain differentiation with T. rubrum and T. intedigitale.

[Onychomycosis: clinical, epidemiological and mycological study in the municipality of São José do Rio Preto]

This was a clinical-epidemiological and mycological study on 184 patients at the university hospital: 200 samples, 142 positive samples, 98 yeasts and 68 filamentous fungi. Candida parapsilosis (47%) and Trichophyton rubrum (38%) were prevalent. They were 100% sensitive to ketoconazole and 99% sensitive to amphotericin B. The highest prevalences were among women (80%), adults (62%) and toes (84%).

Emerging therapeutic agents for onychomycosis

Onychomycosis is a frequent disorder that represents the most prevalent fungal infection, particularly among older individuals. Diverse fungi of the dermatophyte, non-dermatophyte mold and yeast families have been reported to be responsible for onychomycosis. The output from the pharmaceutical industry of new antifungals to treat onychomycosis has been limited over the last decade. Present treatment options include both oral and topical drugs, with oral therapies giving better outcomes. However, neither of these treatment options provides high cure rates that are durable. At present, azoles and allylamines are keeping the pivotal roles. New derivatives with a favorable risk-benefit ratio and new formulations of older azoles seem to be promising. Thus, ongoing drug development activities have focused on novel delivery technologies to facilitate incorporation of existing antifungal drugs inside the nail plate and the discovery of new active antifungals.

In vitro antifungal susceptibility patterns of dermatophyte strains causing tinea unguium

BACKGROUND

Dermatophytes are the major responsible organisms in onychomycosis. Although recent antifungal agents have high success rates in treating this condition, lack of clinical response may occur in 20%. Antifungal drug resistance may be one of the causes of treatment failure. The need for in vitro antifungal drug resistance in daily practice is still under discussion.

OBJECTIVE

We aimed to determine the in vitro susceptibility patterns of dermatophytes causing onychomycosis, against the traditionally available systemic antifungal agents terbinafine, itraconazole and fluconazole.

METHODS

In total, 100 otherwise healthy patients with suspected onychomycosis were included. Nail clippings were cultured on Sabouraud dexrose agar, mycobiotic agar and dermatophyte test medium. Antifungal susceptibility tests were carried out, mainly following The National Committee for Clinical and Laboratory Standards (M38-P) protocol standard for filamentous fungi. Different concentrations of terbinafine (0.008-8 microg/mL), itraconazole (0.015-16 microg/mL) and fluconazole (0.06-64 microg/mL) were tested. Minimum inhibitory concentration end-point determination was chosen as 100% growth inhibition for terbinafine and 80% for azoles.

RESULTS

Of the 100 nail samples, 43% grew dermatophytes. The main causative organism was Trichophyton rubrum (91%) followed by Trichophyton mentagrophytes (9%). Terbinafine had the lowest minimum inhibitory concentration (0.008 microg/mL) followed by itraconazole. Fluconazole showed the greatest variation in minimum inhibitory concentration (0.03-2 microg/mL) and had different susceptibility patterns for the two species.

CONCLUSIONS

Of the three antifungals tested, terbinafine had the most potent in vitro antifungal activity against dermatophytes. Antifungal susceptibility tests would be useful to screen antifungal-resistant dermatophyte strains.

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

Using a reference microdilution method, we studied the antifungal susceptibility to voriconazole and fluconazole of 304 clinical isolates from four species of onychomycosis-causing dermatophytes, 196 isolates of dermatophytes not related to nail infection as well as Scopulariopsis brevicaulis, Fusarium spp. and Scytalidium dimidiatum. Results showed a high antifungal activity of voriconazole against dermatophytes (geometric mean minimal inhibitory concentration (MIC)=1.14 microg/mL; MIC for 50% of the organisms (MIC(50))=0.062 miccrog/mL; MIC for 90% of the organisms (MIC(90))=0.25 microg/mL). For S. brevicaulis, the in vitro activity of voriconazole was considerably lower (geometric mean MIC=8.52 microg/mL; MIC(50) and MIC(90)=16 microg/mL). Although voriconazole is not among the drugs recommended for the management of onychomycosis, it can be a useful alternative for recalcitrant infections.

Molecular typing and antifungal susceptibility of Trichophyton rubrum isolates from patients with onychomycosis pre- and post-treatment

Forty sequential isolates of Trichophyton rubrum were obtained from patients suffering from onychomycosis at two time points, before and after antifungal oral therapy. Strain differentiation by specific amplification of the two tandemly repeated elements (TRS-1 and TRS-2) of the ribosomal DNA of T. rubrum was performed. In addition, susceptibility tests were executed by the microdilution method with nine antifungal drugs: ketoconazole, itraconazole, fluconazole, miconazole, clotrimazole, isoconazole, griseofulvin, cyclopiroxolamine and terbinafine. The combination of TRS-1 with TRS-2 PCR amplification patterns configured 11 T. rubrum genotypes and the three most prevalent (genotypes 1-I, 5-I and 2-I) accounted for 67.5% of the isolates. Seven isolates (35%) obtained before antifungal oral therapy exhibited genotype 1-I compared to the 11 (55%) obtained after the treatment. Twelve patients exhibited different strains before and after the antifungal therapy. With respect to in vitro susceptibility testing, terbinafine was the most potent agent, followed by itraconazole, clotrimazole, isoconazole, miconazole, cyclopiroxolamine, ketoconazole, griseofulvin and fluconazole. Furthermore, an increase in the minimum inhibitory concentrations (MIC) were observed for most of the azole agents when testing isolates obtained post-treatment from four patients. This increase in MIC occurred concomitantly with the major occurrence of genotype 1-I for isolates obtained after oral therapy. These data attempt to consider the relevance of in vivo drug resistance for onychomycosis caused by T. rubrum.