Some remarks concerning Trichophyton proliferans

We have had the opportunity to study an dermatophyte isolated from the face of a woman, as a result of a fall on the ground. We identified the strain as Trichophyton proliferans whose characteristics, together with a review of the works published about this dermatophyte, lead us to believe that we are dealing with an independent species and not a synonym of T. mentagrophytes var. erinacei.

Rapid method for differentiation of Trichophyton rubrum, Trichophyton mentagrophytes, and related dermatophyte species

Bromocresol purple-milk solids-glucose medium, proposed by Fischer and Kane in 1971 (Mycopathol. Mycol. Appl. 43:169-180, 1971) as an aid in the rapid determination of Trichophyton rubrum and Trichophyton mentagrophytes, was evaluated across a wide range of isolates to determine its accuracy and efficacy in the clinical laboratory. Results showed that it facilitated accurate determination of typical and atypical isolates of both species and also permitted the rapid identification of other closely related and similar species. Identification of all dermatophyte species tested was possible within 7 to 10 days. Occult contamination of isolates by antibiotic-resistant bacteria did not hinder identification.

Dermatophyte-hormone relationships: characterization of progesterone-binding specificity and growth inhibition in the genera Trichophyton and Microsporum

We reported previously that Trichophyton mentagrophytes contains a cytoplasmic macromolecule which specifically binds progesterone. Progesterone is also an effective inhibitor of growth of the fungus. We report here studies which characterize more fully the specific binding properties and the functional responses of T. mentagrophytes and taxonomically related fungi to a series of mammalian steroid hormones. Scatchard analysis of [3H]progesterone binding in both the + and - mating types of Arthroderma benhamiae and in Microsporum canis revealed a single class of binding sites with approximately the same affinity as that in T. mentagrophytes (Kd, 1 X 10(-7) to 2 X 10(-7) M). Trichophyton rubrum had a protein with a higher binding affinity (Kd, 1.6 X 10(-8) M). Characterization of the [3H]progesterone-binding sites in T. mentagrophytes showed the binder to be a protein which was destroyed by trypsin and heating to 56 degrees C. Previous examination of the steroid-binding specificity in T. mentagrophytes had demonstrated that deoxycorticosterone (DOC) and dihydrotestosterone (DHT) were effective competitors for [3H]progesterone binding. Expansion of this study to include other competitors revealed that R5020 (a synthetic progestin), androstenedione, and dehydroepiandosterone possessed relative binding affinities which were 20, 11, and 9% of that of progesterone, respectively. Other ligands tested were less effective. Competition studies for the binder in M. canis resulted in similar findings: DOC and DHT were effective competitors for [3H]progesterone binding. The growth of A. benhamiae + and -, M. canis, and T. rubrum were all inhibited by progesterone in a dose-responsive manner, with 50% inhibition achieved at concentrations of 9.8 x 10(-6), 1.2 x 10(-5), 1.5 x 10(-5), and 2.7 x 10(-6) M. respectively,.

Macroconidial development and germination in Trichophyton mentagrophytes

Trichophyton Mentagrophytes was investigated for macroconidial development with particular emphasis on the conidial ageing by light and scanning electron microscopy. Macroconidial germination was also studied under various conditions. Sabouraud glucose agar supplemented with 3% NaCl was used to enhance production of macroconidia. After a long-term cultivation macroconidial compartments changed to spherical thick-walled structure. Some 12-month-old macroconidia were still capable of germination. A wide range of temperature (15-37 degrees C), and inoculum of less than 1 X 10(5) conidia per ml of rich media were appropriate for macroconidial germination. The germination process of macroconidia was highly tolerant to NaCl. A small fraction of the conidia were able to germinate even in distilled water without activation. Effect of freeze-thaw or ultraviolet irradiation on macroconidial germination was determined.

Studies on antifungal agents. 17. Effects of the C-5-substitution on the in vitro activity of novel 3,5-substituted isoxazolidines

A number of novel 5-(substituted thiomethyl)-3-phenyl-3-(1H-imidazol-1-ylmethyl)-2- methylisoxazolidine derivatives were prepared and evaluated in vitro for antifungal activity in solid agar cultures against Trichophyton rubrum, Aspergillus fumigatus and Candida albicans. The effect of the 5-(substituted thiomethyl) group on the degree and scope of activity was studied and compared to that of the corresponding 5-phenoxymethyl and 5-[(substituted phenyl)thio(or amino)methyl] derivatives.

Improved procedures for differentiating Microsporum persicolor from Trichophyton mentagrophytes

Microsporum persicolor, a zoophilic dermatophyte species, is seldom recorded causing human infections in North America. Its identification has been enhanced as a direct result of the development of improved techniques for its characterization. Identifying characteristics include induction of rough-walled macroconidia on sodium chloride-amended medium, absence of good growth at 37 degrees C, and absence of a pH change during growth on casein glucose medium. In contrast, Trichophyton mentagrophytes, a species commonly confused with M. persicolor, has smooth-walled macroconidia, grows well at 37 degrees C, and produces an alkaline reaction on casein glucose medium.

Mating behaviour of Keratinomyces ceretanicus with Arthroderma uncinatum

Keratinomyces ceretanicus was described as a new taxon distinct from Trichophyton ajelloi. Because of the morphological similarity between the two species, their mating behaviour was studied. The optimum temperature for growth of K. ceretanicus was found to be 25 degrees C rather than 17 degrees C. The type culture produced moderate numbers of microconidia on potato glucose agar after 2 weeks at 25 degrees C and a large number of smooth, thick-walled, cylindro-fusiform, 7-to 12-celled macroconidia. On Sabouraud glucose agar containing chloramphenicol and cycloheximide growth was partially but not completely inhibited. When crossed on a soil-hair medium, K. ceretanicus produced fertile gymnothecia typical of Arthroderma uncinatum with 10 (-) mating type isolates of A. uncinatum. As a result, it is concluded that K. ceretanicus is a facultative synonym of T. ajelloi.

Experimental tinea pedis induced by non-abrasive inoculation of Trichophyton mentagrophytes arthrospores on the plantar part of a guinea pig foot

Arthrospores of Trichophyton mentagrophytes were inoculated on to the plantar part of a guinea pig foot by a newly devised non-abrasive method. Anthropophilic and zoophilic isolates required inocula of 280 and 80 arthrospores to infect 50% of inoculated feet, but much larger inocula (5 X 10(4)) were used to establish infection consistently in all feet. Anthropophilic isolate NTM-105 invaded only the upper two-thirds of the horny layer and induced no inflammatory responses. On the other hand, zoophilic isolate SM-110 invaded the whole horny layer and provoked strong inflammatory responses and clinical manifestations. Although the histological features and modes of fungal spreading in the guinea pig skin were quite different between anthropophilic and zoophilic isolate infections, infecting fungi were always recognized in the stratum corneum of all inoculated feet throughout the observation period longer than 6 months. Thus, two types of persistent infections with T. mentagrophytes were established as a guinea pig model of tinea pedis.

Fungicidal activity of human neutrophils and monocytes on dermatophyte fungi, Trichophyton quinckeanum and Trichophyton rubrum

Human peripheral polymorphonuclear neutrophils exhibited potent cytotoxic activity against the dermatophyte fungi Tricophyton quinckeanum and T. rubrum as assessed by inhibition of fungal replication in Sabouraud's agar. Monocytes also showed cytotoxic activity, but this was less pronounced than that of neutrophils, while lymphocytes had no toxic effect. Cytotoxicity showed a linear relationship to the target cell:effector cell ratio, with significant killing detected at a ratio of one neutrophil to one fungal cell. Fungal killing was optimal at incubation times of 2-24 hr for T. rubrum and 2-48 hr for T. quinckeanum. Thereafter, neutrophils were unable to prevent fungal replication while remaining viable. cytotoxicity was markedly reduced by sodium azide, an agent that inhibits haem enzymes, and by catalase, but not by heat-inactivated catalase or superoxide dismutase. The fungicidal activity of neutrophils and monocytes was greatly increased by stimulation with phorbol myristate acetate (PMA) or with concanavalin A (Con A) compounds known to stimulate the secretion of lysosomal enzymes and the production of highly reactive oxygen intermediates. The cytotoxic activity of monocytes to T. quinckeanum, but not to T. rubrum, was also increased by Con A treatment. Neutrophil and monocyte phagocytosis of dermatophytes was demonstrated by electron microscopy studies. Disrupted T. quinckeanum and T. rubrum germlings were identified in the cytoplasm of the phagocytic cells, and similarly disruption of hyphae surrounded, but not engulfed, by neutrophils was also observed. These studies suggest that phagocytosis and/or oxidative products of the respiratory burst of neutrophils and monocytes may be implicated in the killing of dermatophytes in vivo.

Relationship between Candida albicans producing proteinase (CAPP) and its environmental pH--comparison with a case of trichophyton mentagrophytes

Candida albicans produced a karatinolytic proteinase (KPase) or C. albicans producing proteinase (CAPP), a proposed new term for this enzyme, and Trichophyton mentagrophytes also produced KPase when cultivated in liquid medium containing human stratum corneum (HSC) as the nitrogen source, but were unable to do so when cultivated in sabouraud dextrose broth. Purified KPase from the culture supernatants of C. albicans had a molecular weight of 42,000 and an optimum pH at 4.0. The KPase was found to belong to the carboxyl proteinases group and its activity was strongly inhibited by pepstatin. Both fungi were able to grow by secreting KPase which digested HSC for nutrients. KPase from both fungi had high activity in each optimum pH, such as weakly acidic pH on C. albicans and neutral pH on T. mentagrophytes to adapt their surrounding environment by changing the environmental pH into their own optimum pH.

Progesterone binding and inhibition of growth in Trichophyton mentagrophytes

Specific binding of [3H]progesterone to cytosol of Trichophyton mentagrophytes was demonstrated. Scatchard analysis of [3H]progesterone binding showed a single class of binding sites with a dissociation constant of 9.5 X 10(-8) [corrected] +/- 2.4 X 10(-8) M (standard deviation) and a maximal binding capacity of 4,979 +/- 3,489 fmol/mg of cytosol protein. Deoxycorticosterone and dihydrotestosterone competitively inhibited binding by 50% at molar ratios of 10:1 and 20:1, respectively. Other steroid hormones that were tested had minimal activity, indicating binding specificity. Steroid hormone actions in T. mentagrophytes were examined in growth studies. Growth was assessed by determination of cellular ATP content. Progesterone inhibited growth in a dose-responsive manner, with a 50% inhibition concentration of 5.5 X 10(-6) M. Partial recovery from inhibition occurred after 24 to 48 h; inhibition could be enhanced by dividing the amount of added progesterone every 24 h. In the same rank order as was their relationship to each other and progesterone in binding studies, deoxycorticosterone and dihydrotestosterone were less effective inhibitors; other steroid hormones that were tested showed no consistent effect. We hypothesize that the binder described, acting as a hormone receptor, is the molecular site of action for the functional effect of the hormone. The functional effect may be related to the observed resistance of females to dermatophytosis.

[An outbreak of Trichophyton mentagrophytes infection in a rat breeding stock and its successful control]

An outbreak of dermatophytosis by Trichophyton mentagrophytes infection was observed in a breeding stock of the Wistar-Imamichi rat. Typical cutaneous lesions such as alopecia and hyperkeratosis due to the fungus were observed in 10% and 44% of adult females, and males respectively. No infection was seen in infant, even in those fostered by infected females. By 3 repeated cultivations of the hair, T. mentagrophytes was isolated from 107 (90.7%) of 118 rats clinically diagnosed as dermatophytosis. In order to maintain the original stock, the usual wholesale slaughter program was avoided and the following control measures were taken. After sacrificing all rats with the cutaneous lesions, the breeding colony was transferred temporarily to a separate animal room. The resulting vacant room was then disinfected 3 times with 10% formalin, followed by spraying with 3% sodium propionate solution 3 month later. The progenies from the non-infected mothers were dipped into 3% sodium propionate solution and transferred back into the disinfected animal room for re-colonization. Frequent sterilization of all equipment with iodophor, balsam and formalin was carried out. The room sterilized monthly with iodophor and 70% alcohol. Daily observation of all rats and monthly screening by culture test was done thereafter. As a result, no infection has been detected 4 month after recolonization, except for the 3 rats which were sacrificed immediately after detection. On the basis of the culture test and clinical observation, no infection was observed in the treated rat colony for the next five following years. Therefore, the effectiveness of these procedures of the eradication of T. mentagrophytes infection from a rat colony was shown to be quite reliable.

The mode of antifungal action of tolnaftate

The anti-dermatophyte agent tolnaftate was compared with the allylamine antifungal compounds naftifine and terbinafine. Tolnaftate was shown to inhibit sterol biosynthesis at the level of squalene epoxidation and squalene was shown to accumulate in dermatophytes grown in its presence. Biochemical studies in whole and broken cells supported this conclusion and showed that the compound was active against squalene epoxidation in broken C. albicans cells, but was much less potent against whole cells. These results suggested there was a barrier to penetration in these yeasts.

Variability of biochemical characteristics in strains of Trichophyton mentagrophytes

The characteristics of 23 strains of Trichophyton mentagrophytes isolated from clinical samples, were studied. Sabouraud agar was the most adequate medium to inhance at their utmost the different taxonomical features. Variability of enzymatic reactions in strains of T. mentagrophytes was observed.

Inhibition of hyphal development in Trichophyton mentagrophytes arthroconidia by ketoconazole and miconazole

In the presence of 0.5 mg/l ketoconazole and miconazole, arthroconidia from three isolates of Trichophyton mentagrophytes produced germ tubes, which continued to grow for 12 h before further elongation ceased. Lower concentrations reduced the rate of elongation, but did not halt the process. Higher concentrations had no greater effect than 0.5 mg/l. The inhibitory effect of ketoconazole was independent of time of addition of drug during the first six hours of germination. Ketoconazole inhibition was reversible after 12 h contact, whereas miconazole inhibition was not. Morphological effects of drug treatment were investigated by scanning electron microscopy. In the absence of imidazoles, hyphae were straight and regular; ketoconazole treated hyphae were short, irregular and branching; miconazole treatment produced extensive debris and spores forming within the hyphae were visible.

Effect of hydrocortisone on Trichophyton rubrum growth in human epidermal keratinocyte cultures

A large volume of evidence suggests that topical steroids intensify fungal infections. To verify this observation further, we inoculated Trichophyton rubrum into human epidermal keratinocyte cultures in the presence of hydrocortisone. Our results reveal that hydrocortisone does stimulate mycelium growth. However, it only occurs in the cultures containing human epidermal cells, and the stimulation is greater at a higher concentration of the drug (20 micrograms/ml) than a lower one (2 micrograms/ml).

Monitoring of filamentous fungal growth by in situ microspectrophotometry, fragmented mycelium absorbance density, and 14C incorporation: alternatives to mycelial dry weight

Monitoring of filamentous fungal growth by spectrophotometry is generally considered not feasible. This report describes the monitoring of growth of the filamentous fungi Trichophyton mentagrophytes, Rhizopus oryzae, and Sporothrix schenckii in broth by two new spectrophotometric methods and by 14C incorporation from [U-14C]glucose. Microcultures (200 microliter) were prepared in 96-well, flat-bottom microtiter trays, and macrocultures (4 ml) were prepared in glass vials proportionally scaled up from microcultures. Mycelium accumulation in microcultures was measured without terminating the cultures by in situ microspectrophotometry. Accumulation in macrocultures was monitored by uniformly fragmenting the mycelium with a Broeck tissue grinder and by measuring absorbance density in plastic cuvettes with a dual-beam spectrophotometer. Absorbance measurements were found to increase linearly with mycelial weight. In situ absorbance correlated with absorbance density of fragmented mycelium, indicating that both methods monitored growth equivalently. Both defined lag-, exponential-, and stationary-growth phases. Increases in 14C incorporation, absorbance, and mycelial dry weight were kinetically identical for macrocultures and microcultures of T. mentagrophytes. For R. oryzae and S. schenckii, with the exception of R. oryzae growing in microcultures, incorporation of 14C also defined lag, exponential, and stationary growth after selection of the appropriate isotope-specific activity. This incorporation correlated directly with absorbance. We conclude that in situ microspectrophotometry, fragmented mycelium absorbance density, and, to a lesser extent, 14C incorporation can be used to effectively monitor filamentous fungal growth.

Mycoversilin, a new antifungal antibiotic. III. Mechanism of action on a filamentous fungus Trichophyton rubrum

Mycoversilin is active against filamentous fungi, being specifically inhibitory to Trichophyton rubrum, minimum inhibitory concentration being 15 micrograms/ml. Mycoversilin inhibits sporulation to the extent of 28.5% even at the growth inhibitory concentration whereas inhibition of spore germination requires higher concentration. It has no effect on radial growth. Further it shows no action either on the release of UV absorbing materials or on the respiration of T. rubrum. However, the antibiotic inhibits in vivo synthesis of protein fairly strongly, DNA moderately and RNA slightly at the minimum inhibitory concentration. Cell-free protein synthesis is also strongly inhibited, the site of action being the inhibition of leucyl-tRNA formation by the antibiotic which has no action on leucine activation.

The sensitivity of mycelium, arthrospores and microconidia of Trichophyton mentagrophytes to imidazoles determined by in-vitro tests

With mycelium, arthrospores and microconidia of trichophyton mentagrophytes as inocula, a variety of in-vitro tests were used to assess the antifungal activity of the imidazoles; miconazole, clotrimazole, ketoconazole, econazole and tioconazole. For mycelial sensitivity, an agar plus method, a microtitre method using fragmented mycelial suspension and a turbidometric method were employed to determine fungistatic effects while a mycelial plug method indicated fungicidal activity. Spore susceptibility was determined by broth dilution and agar dilution methods for fungistatic action, while fungicidal activity was determined by measurement of rate of kill. The results obtained were affected to varying degrees by the test procedure, temperature and time of incubation, medium, pH and solvent. The spore forms were not more resistant than mycelium to the fungistatic effects of the imidazoles. There was little to choose between the various imidazoles in respect to their performance in these tests, with the exception of ketoconazole, which consistently gave higher MICs.

Fungistatic mechanism of human transferrin for Rhizopus oryzae and Trichophyton mentagrophytes: alternative to simple iron deprivation

Human serum, human transferrin (TF), and the iron chelator 1,10-phenanthroline (OP) produce iron-reversible fungistatic activity which has been attributed to simple iron deprivation. In this study, the influence of the size of the inoculum on the inhibitory activity of serum, TF, and OP prepared with the same iron-binding capacity (2.5 micrograms/ml) for Rhizopus oryzae and Trichophyton mentagrophytes was examined. Inhibition was monitored in liquid microcultures maintained at 37 degrees C and pH 7.4 to 7.5 by measuring the change in absorbance density. Increasing the number of spores in the inoculum disrupted the fungistatic activity of serum and TF, but not that of OP. The dilution at which OP lost fungistatic activity was not affected by the number of spores in the inoculum and was the same for both fungi. The dilution at which TF and serum lost fungistatic activity was dependent upon both the quantity of the inoculum and the species of fungus. The number of viable spores, rather than the total number of spores in the inoculum, was determined to be important in overcoming the inhibition of fungal growth by serum and TF. The fungistatic activity of serum and TF could be diminished by the preexposure of the serum to viable but nongrowing spores. Direct and indirect fluorescence studies indicated that both T. mentagrophytes and R. oryzae absorbed TF. Glucose uptake by R. oryzae was inhibited by a 4-h exposure to 5.0 to 0.15 mg of apotransferrin per ml. These results suggest that the fungistatic activity of TF for R. oryzae and T. mentagrophytes may not be attributable to simple iron deprivation and raise the possibility of a requirement for a direct interaction.