Isolates Of Trichophyton Rubrum Research Articles

Antifungal susceptibility and genetic similarity of sequential isolates of Trichophyton rubrum from an immunocompetent patient with chronic dermatophytosis.

Chronic cutaneous dermatophytoses caused by Trichophyton rubrum are common in immunocompromised patients. In immunocompetent indivuals, the disease is more often associated with onychomycosis and tinea pedis. The aim of this study was to perform antifungal susceptibility tests and genetic analysis of sequential isolates of T. rubrum from an immunocompetent patient with chronic dermatophytosis. Antifungal susceptibility tests against griseofulvin, ketoconazole, itraconazole and fluconazole were performed with sequential isolates of T. rubrum. Genetic relationship among the isolates was analysed by the random amplification of polymorphic DNA (RAPD) method. The results revealed that treatment failure was not related to the development of drug resistance, as all of the sequential T. rubrum isolates were sensitive to antifungals tested in vitro. The RAPD data demonstrated that this disease was caused by identical isolates, with no genetic differences among them, representing a single T. rubrum strain. Treatment failure and chronicity of infection do not seem to be related to antifungal resistance.

Anti-Dermatophytic Activity of Some Indian Medicinal Plants

Objective: Anti-dermatophytic activities of 23 South Indian medicinal plant materials have been studied using five isolates of Trichophyton rubrum and four isolates of Trichophyton mentagrophytes obtained from the patients of Raja Muthiah Medical College & Hospital, India and compared. Materials and methods: Water and ethanol extracts were prepared and their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined. Results and conclusion: Ethanol extracts of plants exhibited more activity than water extracts. Among 23 plants garlic showed least MIC & MFC. In addition, ethanolic extracts of 11 plants showed less than 11.5 mg/ml MFC against T. rubrum and 9 plants showed less than 11.5 mg/ml MFC against T. mentagrophytes .

Biochemical characterization of terbinafine-resistantTrichophytonrubrumisolates

We investigated the biochemical basis for resistance in six sequential clinical isolates of Trichophyton rubrum, from the same patient, which exhibited high-level primary resistance to terbinafine. Cellular ergosterol biosynthesis was measured by incorporation of [14C]acetate, and microsomal squalene epoxidase was assayed by conversion of [3H]squalene to squalene epoxide and lanosterol. Direct comparison was made with a terbinafine-susceptible reference strain of T. rubrum in which squalene epoxidase was previously studied. Resistant isolates displayed normal cellular ergosterol biosynthesis, although slight accumulation of radiolabeled squalene suggested reduced squalene epoxidase activity. Ergosterol biosynthesis in the resistant isolates was only inhibited by terbinafine concentrations above 1 microg/ml (IC50 5 microg/ml). In the reference strain, ergosterol biosynthesis was eliminated by terbinafine at 0.03 microg/ml in accordance with historical data. There was no significant difference in sensitivity between the six resistant isolates. Squalene epoxidase from resistant strains was three orders of magnitude less sensitive than normal enzyme to terbinafine (IC50 of 30 micromol/l and 19 n mol/l respectively). The epoxidase in the resistant strains was also unresponsive to tolnaftate. Resistance to terbinafine in these T. rubrum isolates appears to be due to alterations in the squalene epoxidase gene or a factor essential for its activity.

Phenotypic characterization of Trichophyton rubrum isolates from two geographic locations in Brazil.

To characterize possible Trichophyton rubrum phenotypes, which circulate in two Brazilian localities, we tested 53 isolates of this dermatophyte for their ability to assimilate several carbon sources, for keratinase, proteinase, phospholipase, lipase and desoxiribonuclease (DNase) secretions, and for their susceptibility to the antifungals fluconazole, ketoconazole and itraconazole. For each method, the isolates were submitted to similarity analysis and the methods were evaluated for their discriminatory indexes. None of the isolates were capable of assimilating arabinose, dulcitol, lactose, melibiose, ribose and xylose, while all of the isolates assimilated maltose, sucrose and sorbitol. However, adonitol, cellobiose, dextrin, erythritol, fructose, galactose, inulin, mannitol, mannose, raffinose, rhamnose and trehalose were assimilated by some isolates but not by others. All isolates secreted keratinase and DNase, while none secreted phospholipase. Proteinase and lipase were secreted only by some isolates. All but four isolates were resistant to fluconazole, most of them were sensitive to ketoconazole and all were sensitive to itraconazole. Carbohydrate assimilation was the method that presented the highest discriminatory index, and also the method that displayed the largest number of biotypes. Taken together, these data suggest that significant phenotypic variations exist among T. rubrum isolates. They seem to occur independently from their geographic origins.

Cryptocandin, a potent antimycotic from the endophytic fungus Cryptosporiopsis cf. quercina.

A unique lipopeptide antimycotic, termed cryptocandin, is described from Cryptosporiopsis cf. quercina, an endophytic fungus. Cryptocandin, with a molecular mass of 1079 Da, contains equimolar amounts of 3,4-dihydroxyhomotyrosine, 4-hydroxyproline, threonine, glutamine, 3-hydroxy-4-hydroxymethylproline, 4,5-dihydroxyornithine and palmitic acid. Cryptocandin is chemically related to well-known antimycotics, the echinocandins and pneumocandins, which are produced by such fungi as Zalerion arboricola, Pezicula spp. and Aspergillus spp. Cryptocandin has minimal inhibitory concentration values of 0.03-0.07 microgram ml-1 against isolates of Candida albicans, Trichophyton mentagrophytes and Trichophyton rubrum. Cryptocandin is also active against a number of plant-pathogenic fungi including Sclerotinia sclerotiorum and Botrytis cinerea.

In vitro susceptibility ofTrichophyton rubrum isolates to griseofulvin and tioconazole. Induction and isolation of a resistant mutant to both antimycotic drugs

The in vitro susceptibility of three clinical Trichophyton rubrum isolates to griseofulvin and tioconazole, determined by the minimal inhibitory concentration (MIC), was 2 and 0.5 to 1.0 micrograms/ml, respectively. One mutant (gril) obtained after mutagenic treatment of one of these isolates was selected and showed simultaneous resistance to griseofulvin (MIC > 2000 micrograms/ml) and tioconazole (MIC = 1.0 microgram/ml). The clinical importance and the possibility of a multidrug resistance (MDR)-type mechanism being involved in this event is discussed.

The proteolytic activity of strains ofT. mentagrophytesandT. rubrumisolated from tinea pedis and tinea unguium infections

To understand the significance of proteolytic enzymes in the pathogenesis of dermatophyte infections, we have studied the expression of proteolytic activity in vitro. Cultures were extracted after 1, 2, 3, 4 and 5 weeks of growth and the proteolytic activity measured by a peptide release assay using human stratum corneum as a substrate. Maximum activity was noted at 3 weeks which corresponded to the dissolution of the stratum corneum particles. Isolates of Trichophyton mentagrophytes and Trichophyton rubrum from 42 patients with tinea pedis or tinea unguium were established on 2% glucose peptone plates. Using the peptide release assay it was found that after 3 weeks culture, T. mentagrophytes showed higher activity that T. rubrum in tinea pedis (2044 +/- 1067 micrograms protein released h-1 mg-1, n = 13 compared to 828 +/- 614 micrograms protein released h-1 mg-1, n = 13). In tinea unguium, the values at 3 weeks were generally lower. Trichophyton mentagrophytes activity was 837 +/- 121 micrograms protein released h-1 mg-1 (n = 3) compared to 470 +/- 271 micrograms protein released h-1 mg-1 (n = 13) for T. rubrum. Thus, as well as a variation in activity between the two species, there appears to be a variation in site in terms of expression of activity.

Susceptibility of Trichophyton rubrum to griseofulvin

Two hundred and seventy isolates of Trichophyton rubrum from 182 patients were subjected to susceptibility testing with griseofulvin according to Granade & Artis. A slight modification of the method concerning homogenization procedures gave better growth of controls in our investigation. In 245 cases an MIC could be determined. Among these isolates, seven strains from six patients presented MICs between 2 and 3 micrograms griseofulvin per ml, a value which, according to Artis et al., is to be considered as relatively resistant. The other isolates proved to be more susceptible to griseofulvin. Three of the patients showed no indication of therapeutic failure of griseofulvin treatment. The other three patients had onychomycoses of long standing and had been treated with griseofulvin previously with little or limited success. It is our conclusion that griseofulvin susceptibility testing is not a reliable instrument in explaining failure of griseofulvin therapy in Trichophyton rubrum mycoses.

In Vitro Susceptibility of Dermatophytes from Munich to Griseofulvin, Miconazole and Ketoconazole

Various recent clinical isolates of Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum canis and Epidermophyton floccosum from Munich were subjected to antimicrobial susceptibility testing using the microdilution method. Both azoles miconazole and ketoconazole were found to be more active than griseofulvin. Comparatively high inhibitory concentrations of griseofulvin were especially found with Tr. mentagrophytes. On the whole miconazole turned out to be even somewhat more effective than ketoconazole. Considering the minimum inhibitory concentrations found at least some of the strains tested might not be open to eradication in clinical terms with conventional treatment protocols.

Polymorphism in mitochondrial DNA of several Trichophyton rubrum isolates from clinical specimens

Mitochondrial DNA from six isolates of Trichophyton rubrum (a fungal pathogen of humans) was isolated, purified and digested by restriction endonucleases HindIII, HaeIII, AluI and EcoR1. The isolates could be classified into two groups according to their characteristic fragment patterns. Electron microscopy indicated that T. rubrum mitochondrial DNA are circular molecules of different lengths, 26.85 μm and 21.60 μm respectively, according to the group.

In vitro activity of ME1401, a new antifungal agent.

The in vitro antifungal activity of ME1401, a potential topical antifungal agent, was compared with that of haloprogin, clotrimazole, miconazole, tolnaftate, and ciclopirox olamine by using an agar dilution procedure. ME1401 showed a broad antifungal spectrum and inhibited all of the 428 strains of 52 species of pathogenic yeasts and filamentous fungi tested at concentrations ranging from 0.01 to 12.5 micrograms/ml. In general, the activity of ME1401 was comparable or superior to that of clotrimazole and was greater than that of haloprogin and the other reference drugs under the conditions used. Only tolnaftate was superior to ME1401 in its activity against clinical isolates of Trichophyton rubrum. ME1401 showed no cross-resistance with any of the reference drugs and exhibited potent fungicidal activity.

Dermatophytes identified at the australian national reference laboratory in medical mycology 1966-1982

Over a 17 yr period from 1966 to 1982, 4354 dermatophytes were identified at the Australian National Reference Laboratory in Medical Mycology. The most frequently identified species was Trichophyton rubrum, accounting for 35.3% of identifications, followed by Trichophyton mentagrophytes (26.5%), Trichophyton tonsurans (12.8%), Epidermophyton floccosum (10.7%) and Microsporum canis (8.4%). Specimens taken from the feet were the most common source of the Trichophyton rubrum isolates, followed by specimens from the groin. The highest incidence of T. rubrum and other Trichophyton infections was found in males in the age group 21-30 yr. Microsporum species were most commonly isolated from children aged 10 yr or less. In 1.5% of specimens, more than one fungal species was isolated. In most of these instances a yeast (predominantly Candida species) was found in addition to a Trichophyton species.

Comparison of the in vitro antifungal activities of ketoconazole and griseofulvin against clinical isolates of Dermatophytes.

Ketoconazole, a new imidazole derivative, and griseofulvin, are the two most valuable oral antimycotics for oral administration in the treatment of dermatophytosis. The antifungal properties of ketoconazole were compared in vitro with those of griseofulvin using a liquid microculture method and 68 clinical isolates of dermatophytes. Both drugs showed minimal inhibitory concentration (MIC) values of ≤5μg/ml for all isolates of Trichophyton rubrum. The MIC values of griseofulvin for 90% of Trichophyton mentagrophytes isolates ranged from 0.5 to 3μg/ml; the MIC values of ketoconazole for Trichophyton mentagrophytes ranged from 0.5 to 5μg/ml or greater. Microsporum species were 2.3-6.3 times more susceptible to griseofulvin than to ketoconazole; Epidermophyton floccosum was uniquely susceptible to both drugs.

Griseofulvin-Resistant Dermatophytosis Correlates With In Vitro Resistance

The unsuccessful treatment of dermatophytosis with griseofulvin is common. The mechanism is not known but may involve infection with a griseofulvin-resistant dermatophyte. The mean minimal inhibitory concentration (MIC) value of griseofulvin for Trichophyton rubrum isolates obtained from griseofulvin unresponsive patients was substantially larger than the mean MIC value for responsive control isolates. This difference indicates that therapeutic failure does correlate with the relative in vitro resistance. An MIC of 3.0 microgram/mL or greater was determined to indicate relative griseofulvin resistance. We conclude that the MIC determination for griseofulvin can be used to determine the appropriateness of griseofulvin therapy.

Range of variation among isolates of Trichophyton rubrum.

An investigation was made of the morphologic stability of the anthropophilic dermatophyte, Trichophyton rubrum, a causative organism of chronic mycoses of the skin. Seven distinct strains were delineated and described with differing morphological stabilities ranging from highly sporulating, pigmented forms to downy isolates. Stability was confirmed by single microconidiospore cultures.