Evaluation of broth microdilution antifungal susceptibility testing conditions for Trichophyton rubrum

Fifty clinical isolates of Trichophyton rubrum were selected to test with ketoconazole, fluconazole, itraconazole, griseofulvin, and terbinafine by following the National Committee for Clinical Laboratory Standards susceptibility testing guidelines for filamentous fungi (M38-A). In addition, other susceptibility testing conditions were evaluated: (i) three medium formulations including RPMI 1640 (standard medium), McVeigh & Morton (MVM), and Sabouraud dextrose broth (SDB); (ii) two incubation temperatures (28 and 35 degrees C); and (iii) three incubation periods (4, 7, and 10 days). The strains Candida parapsilosis (ATCC 22019), Candida krusei (ATCC 6258), T. rubrum (ATCC 40051), and Trichophyton mentagrophytes (ATCC 40004) were included as quality controls. All isolates produced clearly detectable growth only after 7 days of incubation. MICs were significantly independent of the incubation temperature (28 or 35 degrees C) (P < 0.05). Different incubation periods resulted in MICs which were consistently different for each medium when azoles and griseofulvin were tested (P < 0.05). MICs obtained from different media at the same incubation time for the same isolate were significantly different when azoles and griseofulvin were tested (P < 0.05). MICs were consistently higher (usually 1 to 2 dilutions) with RPMI than with MVM or SDB (P < 0.05). When terbinafine was tested, no parameter had any influence on MICs (P < 0.05). RPMI standard medium appears to be a suitable testing medium for determining the MICs for T. rubrum. MICs obtained at different incubation times need to be correlated with clinical outcome to demonstrate which time has better reliability.

Aminopeptidases and dipeptidyl-peptidases secreted by the dermatophyte Trichophyton rubrum

The nature of secreted aminopeptidases in Trichophyton rubrum was investigated by using a reverse genetic approach. T. rubrum genomic and cDNA libraries were screened with Aspergillus spp. and Saccharomyces cerevisiae aminopeptidase genes as the probes. Two leucine aminopeptidases, ruLap1 and ruLap2, and two dipeptidyl-peptidases, ruDppIV and ruDppV, were characterized and compared to orthologues secreted by Aspergillus fumigatus using a recombinant protein from Pichia pastoris. RuLap1 is a 33 kDa nonglycosylated protein, while ruLap2 is a 58-65 kDa glycoprotein. The hydrolytic activity of ruLap1, ruLap2 and A. fumigatus orthologues showed various preferences for different aminoacyl-7-amido-4-methylcoumarin substrates, and various sensitivities to inhibitors and cations. ruDppIV and ruDppV showed similar activities to A. fumigatus orthologues. In addition to endopeptidases, the four aminopeptidases ruLap1, ruLap2, ruDppIV and ruDppV were produced by T. rubrum in a medium containing keratin as the sole nitrogen source. Synergism between endo- and exopeptidases is likely to be essential for dermatophyte virulence, since these fungi grow only in keratinized tissues.

[Evaluation the antimycotic activity of itraconazole in human stratum corneum with vitro fungi cultivation]

OBJECTIVE

To establish a new model to evaluate the antifungal activity of antimycotics.

METHODS

Twenty-one healthy adult volunteers without clinically significant differences in demographic characteristics, hydration status of the skin, and sebum excretion were randomly divided into two groups: group 1 receiving 200 mg itraconazole bid for 1 week, and group 2 receiving itraconazole 200 mg qd for 1 weeks. Stratum corneum stripping was taken from the forearm skin at days 0, 1, 4, 7, 10, 14, 21, 28, and 35. Spores of selected fungi (Trichophyton rubrum, Trichophyton mentagrophytes, and Microsporum canis) were deposited and cultured on the center of the stratum corneum stripping. After 1-week culture the stratum corneum stripping was staining by PAS, and the area covered by dermatophyte was measured by corneofungimetry and computerized-assisted image analysis so as to calculate the inhibitory effect of the oral antifungal agents administered.

RESULTS

All three dermatophytes grew on the stratum corneum stripping, the area covered by the dermatophyte was dense before administration of antifungal agent, and decreased gradually after the administration of drug, and to the least on the seventh day (P < 0.01), however, the area covered by the dermatophyte began to increase since the tenth day, and reach the biggest on the thirty-fifth day. Itraconazole at two different dosages showed significant activity against these 3 dermatophytes without significant difference between the two groups (all P > 0.05).

CONCLUSION

The ex vivo growth environment of dermatophyte on human stratum corneum is very similar to that of human milieu interne. Itraconazole displays a high antidermatophyte activity in human stratum corneum. Corneofungimetric bioassay is a new method between in vitro trial and in vivo effect.

A novel mycological analysis valuable for evaluating therapeutic efficacy of antimycotics against experimental dermatophytosis in guinea pigs

Although antimycotic effects are mainly evaluated with regard to whether or not the fungi grow from a specimen obtained from the drug-treated skin, the potential for discrepancies in skin specimens in which the fungi are grown has not been evaluated, in the experimental tinea model. In this study, to evaluate the therapeutic effectiveness of antimycotic agents against fungal skin infection, a novel form of mycological assessment, which focuses on the size of colonies grown from skin specimens was examined and developed. When microconidia of Trichophyton mentagrophytes were inoculated onto a Sabouraud dextrose agar (SDA) plate and incubated at 27 degrees C for 5 days, a linear relationship was observed between the growth area of mycelia and the logarithm of the quantity of microconidia. This relationship between the growth area and the logarithm of the number of T. mentagrophytes microconidia did not change with the addition of skin homogenate and/or keratin powder. Next, the number of fungi in skin blocks attendant upon experimental, cutaneous infection in guinea pigs was evaluated and analyzed via a calibration curve, determined based on a microconidium suspension of T. mentagrophytes. Estimates of severity of dermatophytic infection in experimental animals were parallel to, but more reliable than, results obtained via the conventional mycological method (fungus-positive skin ratio of treated skin) in culture studies of infected dermal tissues. This new analytical method may also be applicable to the in vivo assessment of the therapeutic effect against dermatophytosis experimentally produced in guinea pigs.

Antifungal effect of 5-aminolevulinic acid PDT in Trichophyton rubrum

In the present investigation, we have shown for the first time that the onychomycosis-inducing dermatophyte Trichophyton rubrum was able to metabolize 5-aminolevulinic acid (ALA) to protoporphyrin IX (PpIX) in liquid culture medium. We have established and optimized the culture conditions and could show the typical PpIX-induced red fluorescence which was evaluated qualitatively by Wood's light examination and fluorescent microscopic analysis. The optimum concentration of ALA was in the range of 1-10 mmol l(-1). If used in higher concentrations, ALA leads to a significantly reduced growth rate and absence of PpIX formation due to highly acidic conditions. The first observation of red fluorescence was detected between 10 and 14 days poststimulation with ALA, increasing thereafter. Fluorescent microscopic examinations demonstrated that formation of PpIX was restricted to selected parts of the fungal mycelium. Repeated application of ALA in order to achieve the highest formation of PpIX in T. rubrum failed, probably due to the sustained low pH values. ALA treatment and irradiation of T. rubrum clearly demonstrated the growth-inhibiting effect of ALA PDT, either leading to reduced numbers of colonies or reduced diameters of single fungal colonies. Summarizing our results, ALA PDT might be a promising approach in the reduction of T. rubrum colonization in onychomycosis.

Low-voltage direct current as a fungicidal agent for treating onychomycosis

Onychomycosis, most commonly caused by two species of dermatophyte fungi--Trichophyton rubrum and Trichophyton mentagrophytes--is primarily treated with regimens of topical and systemic antifungal medications. This study was undertaken to evaluate in vitro the efficacy of low-voltage direct current as an antifungal agent for treating onychomycosis. Agar plate cultures of T rubrum and T mentagrophytes were subjected to low-voltage direct current electrostimulation, and antifungal effects were observed as zones in the agar around the electrodes lacking fungal growth. Zones devoid of fungal growth were observed for T rubrum and T mentagrophytes around anodes and cathodes in a dose-dependent manner in the current range of 500 microA to 3 mA. Low-voltage direct current electrostimulation has great clinical potential for the treatment of onychomycosis and perhaps other superficial maladies of fungal etiology.

Morphological evidences for onion-induced growth inhibition of Trichophyton rubrum and Trichophyton mentagrophytes

The antifungal activity of onion (Allium cepa L.) on two important dermatophytes, Trichophyton rubrum and Trichophyton mentagrophytes, with special reference to morphological aspects was studied. Growth of both fungi was found to be strongly inhibited by aqueous onion extract (AOE) as a dose-dependent manner. The extract showed fungicidal effect for both fungi at concentrations >3.12% (v/v). The fungus T. mentagrophytes was more affected by the onion as compared to T. rubrum at all concentrations used. Morphological effects of onion exposure were examined in correlation with fungal growth. Corresponding to the growth inhibition, light and electron microscopy observations revealed morphological anomalies in hyphal compartments. The results demonstrated that AOE targets the cell membrane of the fungi as breaking down of both inner and outer membranes with consequent extrution of materials into the surrounding medium. Cytoplasmic membranes and other membranous structures of organelles, such as nuclei and mitochondria, were also disrupted. In correlation to the fungal growth, morphological alterations occurred to a less content for T. rubrum compared with T. mentagrophytes. The hyphae of T. rubrum were found to be mainly affected by converting to resistant forms, i.e., chlamidospores as a consequence of phenotype switching response to AOE. Plasmolysis accompanied by an almost complete depletion and disorganization of cytoplasmic structures were found to be the final event which led to cell death. Ultrastructural evidences obtained from this study strongly support that morphological changes of T. rubrum and T. mentagrophytes caused by AOE are associated with its fungistatic and fungicidal activities. With respect to the morphological results and the preliminary data on fungal biochemistry, a mechanism of action by interacting of AOE with thiol (-SH) groups present in essential compartments of the fungal cells was postulated.

Case reports: tinea corporis in a 13-year-old German girl due to Trichophyton schoenleinii. Fallbericht. Tinea corporis in einem 13jahrigen Madchen verursacht durch Trichophyton schoenleinii

We report the first case of a tinea corporis with partly profound lesions in a 13-year-old girl on her arms, legs and trunk due to Trichophyton schoenleinii but without any lesion on scalp and hair. Moreover, this is the first case of an infection with Trichophyton schoenleinii in Germany since more than 40 years. The diagnosis was confirmed by microscopy of mycological specimens. Other causes of the skin symptoms could be excluded (atopic dermatitis, bacterial or other fungal infection). Clinical and epidemiological aspects of this anthropophile dermatophyte are briefly reviewed.

Bullous tinea pedis in two children. Bullose Tinea pedis bei zwei Kindern

Tinea pedis is a dermatophytic infection with a high prevalence in adults and also occasionally observed in children. We report here two cases of bullous tinea pedis, one due to Trichophyton rubrum in a 6-year-old child and the second due to T. interdigitale in a 10-year-old child. We suggest that, despite the low prevalence of this infection in childhood, a potassium hydroxide test and a culture for fungi should always be performed when a child is examined for an inflammatory eruption of the feet.

Dermatophytes in the rural area of Duzce, Turkey

A total of 227 subjects (112 were male and 115 female), who were residents of the rural region of Duzce, were examined for dermatomycosis. A total of 120 samples (47 nail fragments, 73 skin scales) were collected from 81 patients for mycological analysis on the basis of the results of clinical evaluation. All specimens collected were analysed by direct microscopy and culture. Positive results were detected in the cultures of 53 (44.1%) of the 120 samples. About 46 (86.7%) samples also presented positive results in direct microscopy. In the cases of seven samples positive results were found in culture and negative results with direct microscopy. Both culture and direct microscopy presented negative results in 67 (55.8%) samples. The most frequently isolated aetiological agents were 33 Trichophyton rubrum (62.2%), and nine T. mentagrophytes (16.9%). In conclusion, traditional and religious habits such as cohabitation and performing ritual ablutions may affect the prevalence of dermatophyte infections. The performance of ritual ablutions is not in itself a risk factor for acquiring dermatophyte infection; rather it is not drying the extremities after ablutions, that is the main risk factor for this group. Tinea capitis was not found in any of the subjects in spite of the fact that it is one of the most common infectious conditions in children. This is the first paper to report the prevalence of fungal infections in Duzce, a western Black Sea region of Turkey.

In vitro susceptibility testing of amorolfine in pathogenic fungi isolated from dermatomycosis patients in China. In vitro Empfindlichkeitsprufung mit Amorolfin an pathogenen Pilzen von Patienten mit Dermatomykosen in China

The antifungal susceptibility of isolates from Chinese dermatomycosis patients to amorolfine was investigated following National Committee for Clinical Laboratory Standards (NCCLS) protocols. In total, 383 isolates were tested, including 132 strains from tinea pedis, 148 strains from tinea corporis/cruris, and 103 strains from onychomycosis. The minimum inhibitory concentration (MIC) of amorolfine against dermatophytes ranged from 0.01 to 0.08 microg ml(-1). The MIC(50) and MIC(90) of amorolfine for Trichophyton rubrum were both equal to 0.04 micro ml(-1); for T. mentagrophytes these MICs were 0.04 microg ml(-1) and 0.08 microg ml(-1) respectively; and for Epidermophyton floccosum they were 0.02 microg ml(-1) and 0.04 microg ml(-1) respectively. The MIC range of amorolfine against Candida parapsilosis was 0.5-16 microg ml(-1). MIC(50) and MIC(90) for C. parapsilosis were 0.5 and 2 microg ml(-1). MIC ranges of amorolfine against Scopulariopsis spp. and Acremonium spp. were 0.5-4 and 2-8 microg ml(-1), respectively. Candida albicans, Fusarium solani and Aspergillus flavus required relatively higher concentrations of amorolfine to inhibit their growth (MIC 0.125-64 microg ml(-1), MIC(50) and MIC(90) were 4 and 64 microg ml(-1)). The results demonstrated that amorolfine is the only topical agent that has such a potent antifungal activity and a broad spectrum against a wide range of pathogenic fungi.

Trichoderma spp. Antagonism to the Dermatophyte Trichophyton Rubrum: Implications in Treatment of Onychomycosis

Onychomycosis--the dermatophytic invasion of the nail--is difficult to eradicate with drug treatment. The hyphae of the main invading pathogen, Trichophyton rubrum, are often interwoven with the nail plate, preventing effective anti-mycotic agents from reaching its growing tips. An alternative approach to treat onychomycosis may possibly be the application of a biological control agent against the pathogen. In analogy with the success of biocontrol of phytopathogenic fungi, we screened a series of commercially available Trichoderma strains for potential antagonism between Trichoderma and Trichophyton spp. A wide spectrum of antagonism capacity, ranging from effective overgrowth to no interaction was found, with Trichoderma virens NRRL 26672 being the most effective against the Trichophyton strains tested e.g. T. rubrum NCPF118. Furthermore, T. virens NRRL 26672 grown with T. rubrum NCPF118 hyphae as a carbon source, exhibited enhanced induced secretion of active extracellular chitinases and beta-glucosidases, affecting lysis and sporulation on T. rubrum NCPF118 hyphae. Growth of Trichod. virens NRRL 26672 in poor medium also resulted in secretion of antibiotics active in arresting the growth of T. rubrum NCPF118 inoculum. Our findings may open new directions for the treatment of onychomycosis, either in combination with known medications or as a new "natural" route.

Effects of modified sample collection technique on fungal culture yield: nail clipping/scraping versus microdrill

OBJECTIVE

Onychomycosis requires accurate diagnosis but fungal culture yield is frequently low by routine sampling techniques. The aim of this study was to investigate the utility of nail plate/subungual microdrilling as an alternative to conventional nail clipping/subungual scraping.

METHODS

Patients with clinical evidence of onychomycosis (n=46) were prospectively evaluated for fungal potassium hydroride (KOH) microscopy and culture comparing two sampling techniques: nail clipping versus microdrilling.

RESULTS

Fungal cultures were positive in 48% with 2 additional cases detected by combining both methods. KOH microscopy was positive in 17% cases. Specimen obtained via the microdrill technique gave consistent heavier fungal growth on culture media. Candida species were the most common isolates (82.7% of cases) and were negative on KOH microscopy in 95 % of culture proven cases. The microdrill technique yielded consistent heavier growth on culture media

CONCLUSION

Microdrill technique improves laboratory diagnosis and ultimately treatment of onychomycosis, particularly in patients with repeated KOH microscopy and culture failure despite strong clinical suspicion.

Multiplication of an ancestral gene encoding secreted fungalysin preceded species differentiation in the dermatophytes Trichophyton and Microsporum

Dermatophytes are human and animal pathogenic fungi which cause cutaneous infections and grow exclusively in the stratum corneum, nails and hair. In a culture medium containing soy proteins as sole nitrogen source a substantial proteolytic activity was secreted by Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum canis. This proteolytic activity was 55-75 % inhibited by o-phenanthroline, attesting that metalloproteases were secreted by all three species. Using a consensus probe constructed on previously characterized genes encoding metalloproteases (MEP) of the M36 fungalysin family in Aspergillus fumigatus, Aspergillus oryzae and M. canis, a five-member MEP family was isolated from genomic libraries of T. rubrum, T. mentagrophytes and M. canis. A phylogenetic analysis of genomic and protein sequences revealed a robust tree consisting of five main clades, each of them including a MEP sequence type from each dermatophyte species. Each MEP type was remarkably conserved across species (72-97 % amino acid sequence identity). The tree topology clearly indicated that the multiplication of MEP genes in dermatophytes occurred prior to species divergence. In culture medium containing soy proteins as a sole nitrogen source secreted Meps accounted for 19-36 % of total secreted protein extracts; characterization of protein bands by proteolysis and mass spectrometry revealed that the three dermatophyte species secreted two Meps (Mep3 and Mep4) encoded by orthologous genes.

The pathogenesis of dermatophyte infections in human skin sections

AIM

A novel ex vivo model for the study of adherence and invasion of dermatophytes to the stratum corneum was developed.

MATERIALS AND METHODS

A skin of full epidermis thickness was infected by spores of Trichophyton mentagrophytes and examined after various periods of time by scanning and transmission electron microscopy.

RESULTS

After 12 h of inoculation a tenacious adherence between the spores and the stratum corneum was observed. There was a time dependent increase in the number of spores adhered to this surface. By 24 h, germination had commenced. The initial growth of germ tubes occurred extracellularly to the corneocytes. Three days after inoculation, the most prominent feature was proliferation of fungal hyphae and penetration of mycelium through the outer keratinocyte layer which is followed by invasion of the outer stratum corneum.

CONCLUSION

The model introduced in the present study may contribute to a better understanding of the nature of the interaction between dermatophytes and skin cells in dermatophytosis process.

Essential oil compounds fromAgastache rugosa as antifungal agents againstTrichophyton species

The antifungal activities of the essential oil from Agastache rugosa and its main component, estragole, combined with ketoconazole, one of the azole antibiotics commonly used to treat infections caused by Trichophyton species, were evaluated in this study. The combined effects were measured by the checkerboard microtiter and the disk diffusion tests, against T. erinacei, T. mentagrophytes, T. rubrum, T. schoenleinii and T. soudanense. Susceptibility of the five Trichophyton species to the oil alone, or ketoconazole alone, differed distinctly. The fractional inhibitory concentration indices (FICI) of ketoconazole combined with estragole or A. rugosa essential oil, against the tested Trichophyton species, were between 0.05 and 0.27, indicating synergistic effects. These drug combinations exhibited the most significant synergism against T. mentagrophytes, with FICIs of 0.05 and 0.09 for estragole and the essential oil fraction from A. rugosa, respectively. Isobolograms based on the data from checkerboard titer tests also indicated significant synergism between ketoconazole and the Agastache oil fraction or estragole, against the Trichophyton species evaluated. Trichophyton susceptibility to ketoconazole was significantly improved by combination with the Agastache rugosa oil fraction or its main component, estragole.

Onychomycosis caused by an isolate conforming to the description ofTrichophyton raubitschekii

Trichophyton raubitschekii is currently regarded as a synonymous name betokening a variant form of Trichophyton rubrum. Nonetheless, isolates conforming to this morphotaxonomic concept have morphological, physiological and clinical features very different from those of typical T. rubrum. Isolates are mainly obtained from subjects originating from certain tropical and subtropical countries, and are mainly obtained from upper body skin infections, rarely from onychomycosis. In this paper the authors report the first known Italian case of onychomycosis caused by such an isolate. The patient, a male student from Cameroon, had a typical fingernail tinea unguium, without any other sign of skin or nail infection. 'T. raubitschekii' was identified on morphological and physiological grounds by the following features: velvety colony surface, brownish pigment, abundant macroconidia and microconidia, and positive urease activity. Such isolates may prove very difficult to identify correctly, especially in areas like Italy where T. rubrum is normally seen only as isolates presenting a strongly differing phenotype.

Adult Tinea Capitis Due to Trichophyton Violaceum in China

Tinea capitis is rare in adults. We report a case of adult tinea capitis due to Trichophyton violaceum in China. The female patient was immunosuppressed with prednisone due to the underlying disease of vulgaris pemphigus and was treated successfully with terbinafine. We also reviewed published cases of adult tinea capitis in China and compared these data with the characteristics of published cases in other regions in the world.

Ascospore-derived isolate ofArthrodermabenhamiaewith morphology suggestive ofTrichophytonverrucosum

Sixty-one ascospores were isolated from an ascocarp produced by the mating of two Arthroderma benhamiae strains, RV 26678 and KMU4169, that differed in their mitochondrial DNA (mtDNA) restriction fragment length polymorphism (RFLP) patterns and in the sequences of their nuclear ribosomal internal transcribed spacer (ITS) regions. RV 26678 is a genetically typical A. benhamiae isolate, while KMU4169, though morphologically indistinguishable from A. benhamiae, is an isolate with a deviating ITS sequence and with a mtDNA RFLP profile identical to that of T. verrucosum. One of the 61 progeny ascospores formed a colony, KMU5-46, that was quite different from both parental isolates. KMU5-46 is a faviform colony morphologically similar to Trichophyton verrucosum, although its mtDNA RFLP patterns and ITS sequences were identical to those of A. benhamiae parental strain RV 26678. The morphological alteration manifested in KMU5-46, as well as this isolate's complete loss of sexual response, indicates the possibility that the asexual T. verrucosum and the sexual A. benhamiae are conspecific.

Arthroconidial formation in Trichophyton raubitschekii

Arthroconidia produced by dermatophytic fungi are considered to be the primary cause of skin and nail infections in humans and animals. Trichophyton rubrum is currently the most common cause of tinea pedis all over the world. The common form of T. rubrum produces a cottony colony in cultures that is characteristically low in conidia formation. The attempts to produce arthroconidia in T. rubrum have shown little success so far. Recently, Trichophyton raubitschekii, an anthropophilic dermatophyte prevalent in Asia, Africa, and the Mediterranean, has been recognized as a variant of T. rubrum. In cultures, T. raubitschekii is characterized by a granular colony form, and an abundance of both micro- and macroconidia. The present study reveals a predominance of arthroconidia in two T. raubitschekii cultures isolated from clinical materials. These isolates were able to maintain arthroconidiation in bimonthly subcultures throughout the entire course of this study. The growth parameters for in vitro cultivation of arthroconidia are described here. Arthroconidia prepared from T. raubitschekii cultures showed greater than 95% germination within 21 h of suspension in phosphate-buffered saline. The availability of arthroconidia in T. raubitschekii cultures appears to offer a practical means of characterizing infective cells in T. rubrum.

Achievement of complete mycological cure by topical antifungal agent NND-502 in guinea pig model of tinea pedis

We examined the therapeutic effect of a 1% cream preparation of NND-502, a novel topical antifungal agent, in a guinea pig tinea pedis model produced by infecting the plantar skin of guinea pigs with Trichophyton mentagrophytes. Animals developing tinea pedis were divided into two groups: an untreated control group and a treated group. In the latter group, after confirming infection had been established, the infected animals were topically treated with the NND-502 cream once daily for one week. The animals were reared in a clean environment free from exposure to exogenous dermatophytes. At one week (5 weeks post-infection), 6 weeks (10 weeks post-infection) and 16 weeks (20 weeks post-infection) after completion of the treatment, plantar skin samples were taken from a certain number of both groups of animals. The results demonstrated that all of the animals in the untreated control group and none of those in the treated group were culture-positive in this animal model of tinea pedis. The topical treatment with NND-502 achieved a mycological cure. Thus NND-502 can be considered a promising candidate as a new anti-dermatophytic agent for topical use.

Novel high energy intermediate analogues with triazasterol-related structures as inhibitors of ergosterol biosynthesis. III. Synthesis and antifungal activity of N4-alkyl-1,6,7,11b-tetrahydro-2H-pyrimido[4,3-a]isoquinolin-4-amine salts

A series of N4-alkyl-1,6,7,11b-tetrahydro-2H-pyrimido[4,3-a]isoquinolinamine hydroiodides with triazasterol-related structures was designed and synthesized to mimic, as stable analogues, native high energy intermediates (HEI) of ergosterol biosynthesis. The title compounds can be regarded as 8,13,15-triaza-13,17-secosteroids with aromatic ring A bearing the positive charge in the guanidinium moiety. Hence, these compounds present structural similarities with corresponding carbocationic intermediates occurring during the enzyme catalyzed transformation of squalene into ergosterol. The N4-alkylaminopyrimidoisoquinolinium salts were prepared by reaction of respective S-methylthiotetrahydropyrimidoisoquinoline hydroiodides with octylamine, and appropriately methyl-branched alkyl- and alkenylamines. In order to prepare (3R)-6-isopropyl-3-methyl-6-hepten-1-amine several synthetic routes were investigated. The structures of all reported compounds were proved and completely assigned on the basis of homo- and heteronuclear correlated 1D and 2D NMR spectroscopy. The in vitro antifungal susceptibility tests of the title compounds with a standard panel of eight pathogenic fungi revealed especially against the used dermatophytes and yeasts with MICs in the range of 1-32 microg/ml moderate to good antimycotic effects. Depending on the nature of the N4-alkyl substituents structure-activity relationships were found with a maximum of antifungal efficacy of the N4-3,7-dimethyloctylaminopyrimidoisoquinolinium iodide.

Rylux BSU stimulates spore germination in Trichophyton mentagrophytes and Aspergillus fumigatus and increases the survival rate after UV-irradiation

Calcofluor-allied optical brightener Rylux BSU stimulated spore germination rate in Trichophyton mentagrophytes and Aspergillus fumigatus both if supplemented into Sabouraud glucose agar and if used for pretreatment of spore suspension prior to inoculation at low concentrations. Maximum stimulation of germination was obtained if 0.2% Rylux BSU was used for pretreatment in aqueous solution for 1 d prior to inoculation (130% in T. mentagrophytes and 150% in A. fumigatus, respectively). Pretreatment with 1% Rylux BSU provided strong protection against UV-irradiation and resulted in increased yields of cultural variants after UV-irradiation.

Inhibition of dermatophytes by optical brighteners

The aim of this study was to investigate a possible effect of optical brighteners on the growth of dermatophytes. Typical strains of Trichophyton rubrum, T. mentagrophytes, Microsporum canis and Epidermophyton floccosum were grown on agar plates containing two different brighteners of stilbenedisulfonic acid type in concentrations between 5 x 10(-5) and 1 x 10(-2) mol l-1 and their thallus diameters were compared with controls. In addition, hyphae grown with brighteners were compared with controls by fluorescence microscopy and by transmission electron microscopy. Both brighteners had a significant dose-dependent growth-suppressive effect on all dermatophytes tested, that was complete at a concentration of 10(-2) and 10(-3) mol l-1, respectively. Fluorescence microscopy of hyphae showed a pronounced fluorescence of the septal areas and a less-intense staining of the outer cell walls. Electron microscopy revealed a marked thickening and blurred contours of the cell walls grown with brighteners. These new observations relate very well to an interference of optical brighteners with the formation of normal chitin fibrils as described previously. Optical brighteners of stilbenedisulfonic acid type may be rewarding objects for the development of new antifungal agents.

A novel method using micropig stratum corneum in vitro for the evaluation of anti-Trichophyton mentagrophytes activity

Antifungal susceptibility testing under conditions close to clinical status is expected to provide more helpful information than that obtained by a conventional microdilution method. For this purpose, we developed a novel method to evaluate anti-Trichophyton mentagrophytes activity of antifungal agents in vitro by using disks of micropig stratum corneum epidermis (SCE). Basal agar medium containing K2HPO4, MgSO4, CaCl2 and three kinds of antibiotics. Bifonazole (BFZ), lanoconazole (LCZ) or terbinafine (TBF) was added to the basal agar medium to give serially doubling dilutions ranging from 0.0006 to 10 microg/ml. Five-hundred-microl portions of the agar media thus prepared were solidified in wells of flat-bottomed plates. SCE disks (6 mm in diameter) were placed on surfaces of the agar medium and 10(4) conidia of T. mentagrophytes were inoculated on each SCE disk. There was very good correlation between the initial concentration of the antifungal agents added to the basal agar medium (microg/ml) and the concentration of the agents impregnated into the SCE disks (microg/g) (r2>0.99). The minimum inhibitory concentration (MIC) values of BFZ, LCZ and TBF were respectively 26-, 10- and 78-times higher than those measured by the standard microdilution method. From the correlation between the concentration of the agents in the basal medium and that in the SCE disks, the above MIC values corresponded to the concentrations in SCE disks (microg/g), 832.95 for BFZ, 1.42 for LCZ and 8.87 for TBF. This novel method of antidermatophytic susceptibility testing using SCE would be useful as an in vitro screening of proper antimycotics for topical treatment of dermatophytosis.