Advances in dermatophytes and dermatophytosis

Potential of propolis antifungal activity for clinical applications

The high incidence of skin diseases of microbial origin along with the widespread increase of microbial resistance demand for therapeutic alternatives. Research on natural compounds has been opening new perspectives for the development of new therapies with health positive impacts. Propolis, a resinous mixture produced by honeybees from plant exudates, is widely used as a natural medicine since ancient times, mainly due to its antimicrobial properties. More recently, antioxidant, anti-tumor, anti-inflammatory, hepatoprotective and immunomodulatory activities were also reported for this natural product, highlighting its high potential pharmacological interest. In the present work, an extensive review of the main fungi causing skin diseases as well as the effects of natural compounds, particularly propolis, against such disease-causing microorganisms was organized and compiled in concise handy tables. This information allows to conclude that propolis is a highly effective antimicrobial agent suggesting that it could be used as an alternative skin treatment against pathogenic microorganisms and also as a cosmeceutic component or as a source of bioactive ingredients.

Low in vitro activity of sertaconazole against clinical isolates of dermatophyte

Background and Purpose:

Dermatophytes are a group of fungi specialized in invading humans and other vertebrate keratinized tissues. These fungi cause a variety of skin, nail, and hair disorders, called dermatophytosis (tinea). In some cases, drug resistance to antifungals necessitates special treatment. Among the antifungal agents, sertaconazole (i.e., a third-generation imidazole) has a broad-spectrum against dermatophyte species. Regarding this, the present study was conducted to investigate the antifungal susceptibility of dermatophytes obtained from patients with dermatophytosis in Mashhad located in northeastern Iran.

Materials and Methods:

A total of 75 clinical dermatophyte isolates, including Trichophyton mentagrophytes (n=21), T. interdigital (n=18), T. tonsurans (n=16), Epidermophyton floccosum (n=11), Microsporum canis (n=5), Nannizzia fulvum (n=2), T. benhamiae (n=1), and T. verrucosum (n=1), were evaluated against five antifungal agents of sertaconazole, itraconazole, clotrimazole, terbinafine, and griseofulvin based on the CLSI M38-A2 guideline.

Results:

According to the results, the minimum inhibitory concentration (MIC) ranges ofsertaconazole, terbinafine, griseofulvin, itraconazole, and clotrimazole were estimated at 0.125-16, 0.002-1, 0.5-4, 0.031-4, and 0.016-4 µg/ml, respectively, for dermatophyte species. In addition, the geometric mean (GM) values of the MIC of sertaconazole, terbinafine, griseofulvin, itraconazole, and clotrimazole were obtained as 3.39, 1, 1.44, 1.52, and 1.93, respectively.

Conclusion:

Among the tested antifungals, terbinafine and griseofulvin were the most effective agents against dermatophyte isolates. However, sertaconazole, a third-generation imidazole, did not show any significant effect. Furthermore, M. canis and E. floccosum showed the best response to the antifungal agents.

[A brief history of time: 1945-2008--studies, manuscripts, and publications]

I (the author), Tadahiko Matsumoto, who is a winner of the 2008 Japanese Society for Medical Mycology (JSMM) Award, was born in 1945 and graduated in 1969 from Kyushu University in Fukuoka, Japan with an M.D. degree. At the Department of Dermatology, Kyushu University I studied dermatology and medical mycology. In Tokyo (1970-1971) at the Department of Microbiology, National Institute of Hygienic Sciences I learned general mycology. During the period from 1981 to 1983 I further studied medical mycology at the Division of Mycotic Diseases (Director: Dr. Libero Ajello), Center for Infectious Diseases, Centers for Disease Control (CDC) in Atlanta, Georgia in the United States. During the period from 1991 to 2005 while working as Director of Dermatology of Toshiba Hospital in Tokyo I was affiliated with several medical schools as a clinical and adjunct professor. Being a unique physician-scientist eager to publish my manuscripts in highly-regarded mycology journals, my studies were accurately reported as to description, taxonomy, and identification. My articles were published in journals carefully chosen for my purposes. As I became better known, I was frequently invited to contribute review articles in leading journals and chapters in authoritative textbooks of dermatology, infectious diseases, and microbiology. I was also invited to be a member and/or chairperson of various symposia in international congresses and one of the lecturers in seminars. I have established many friendly personal relationships among scientists, and we are always ready to help each other whenever necessary.

Clinicopathologic presentations of dermatomycoses in cancer patients

Many of the skin fungal infections in cancer patients may look similar to those infections in non-cancer patients. However, in some cases, they become more extensive and even life threatening. Prolonged and severe neutropenia is the main risk factor for the dramatic issue of fungal infections. The dermatomycoses in cancer patients can be classified in four broad groups: primary superficial dermatophytoses, primary superficial yeast infections, opportunistic mold infections with distinct potential for dissemination and secondary cutaneous manifestations of fungaemia. Occasionally, more than one fungus are found inside a given skin lesion. A special condition is represented by the mycotic colonization of mucosal squamous cell carcinomas. Angio-invasion by fungi accounts for the frequency of disseminated infections prevailing in immunocompromised cancer patients. In case of skin involvement, the dermatologist may assist by recognizing subtle semiological signs and performing biopsies for swift histological examination, molecular biology and/or culture.

Developments in fungal taxonomy

Fungal infections, especially those caused by opportunistic species, have become substantially more common in recent decades. Numerous species cause human infections, and several new human pathogens are discovered yearly. This situation has created an increasing interest in fungal taxonomy and has led to the development of new methods and approaches to fungal biosystematics which have promoted important practical advances in identification procedures. However, the significance of some data provided by the new approaches is still unclear, and results drawn from such studies may even increase nomenclatural confusion. Analyses of rRNA and rDNA sequences constitute an important complement of the morphological criteria needed to allow clinical fungi to be more easily identified and placed on a single phylogenetic tree. Most of the pathogenic fungi so far described belong to the kingdom Fungi; two belong to the kingdom Chromista. Within the Fungi, they are distributed in three phyla and in 15 orders (Pneumocystidales, Saccharomycetales, Dothideales, Sordariales, Onygenales, Eurotiales, Hypocreales, Ophiostomatales, Microascales, Tremellales, Poriales, Stereales, Agaricales, Schizophyllales, and Ustilaginales).

Morphological study of Trichophyton rubrum: ultrastructural findings after treatment with 4-amino-3-methyl-1-phenylpyrazolo-(3,4-c)isothiazole

The antifungal activity of 4-amino-3-methyl-1-phenylpyrazolo-(3,4-c)isothiazole was studied on Trichophyton rubrum. The compound, at concentrations between 20 and 10 microg ml(-1), induces a remarkable reduction in the growth and causes deep morphogenetic anomalies. The ultrastructural modifications have demonstrated that the compound targets the cell membrane of the fungus, breaking down not only the endomembrane system, but also the 'outer' membrane, with consequent extrusion of materials in the medium. The results suggests a mechanism of action similar to other azoles clinically utilized.

Ultrastructure of the ascospore formation of Arthroderma simii

Ascospore formation of Arthroderma simii was observed using electron microscopy. Using scanning electron microscopy, many round asci were observed inside the gymnothecia obtained by 4 weeks of incubation after mating. Ascospores were produced inside the asci, then discoid-shaped mature ascospores were observed through the degenerate and disrupted ascus cell wall. Disseminated ascospores were observed outside the gymnothecium 7 weeks after inoculation. Using transmission electron microscopy, the enveloping membrane system of two unit membranes invaginated and delimited the cytoplasm. The inner membranes were found to have changed into ascospore plasma membranes, whereas the outer membranes and intercisternal space were changed into ascus cell wall. The subcellular events of ascospore formation were found to be essentially similar to those of other dermatophytes.

Effect of glucose and thiamine concentrations on the formation of macroconidia in dermatophytes. Occurrence of dysgonic Microsporum canis strains in Athens, Greece

Data collected from multiple trials with 110 fresh and preserved clinical isolates of Trichophyton mentagrophytes var. mentagrophytes, T. violaceum, T. rubrum, T. verrucosum, Microsporum canis and Epidermophyton floccosum revealed that production of macroconidia depends on glucose and thiamine concentrations in the medium. Optimal macroconidia production was obtained at the critical concentrations of 5 g l-1 glucose and 0.6 g l-1 thiamine when the two compounds were used in combination. The same conditions also encouraged macroconidia production in aconidial strains of T. verrucosum. Cutaneous inoculation in immunocompetent laboratory rabbits further enhanced the macroconidia producing capacity of the tested strains. Emphasis was placed on the occurrence of dysgonic/atypical strains of M. canis, which readily reverted to their typical phenotypes after growth on medium supplemented with 0.6 g l-1 thiamine, a process greatly augmented after cutaneous animal inoculation. It was verified that selective exogenous factors affect macroconidial production and that the dysgonic group of M. canis constitutes an epidemiologically significant group in the Greater Athens area. This is the first report of the occurrence of such M. canis strains from Greece.

Dermatophytes: gross and microscopic

Dermatophytes, members of the anamorphic genera Epidermophyton, Microsporum, and Trichophyton, are capable of invading keratinous tissue, causing cutaneous infection referred to as dermatophytosis. These species may be anthropophilic, zoophilic, or geophilic based on host preference and natural habitat. These groupings are epidemiologically significant. This article provides a description of the genera and species of the dermatophytes--gross and microscopic--and the tests that may be necessary to confirm their identification.

The dermatophytes

The etiologic agents of the dermatophytoses (ringworm) are classified in three anamorphic (asexual or imperfect) genera, Epidermophyton, Microsporum, and Trichophyton. Species capable of reproducing sexually belong in the teleomorphic genus, Arthroderma, of the Ascomycota. On the basis of primary habitat association, they may be grouped as geophilic (soil associated), zoophilic, and anthropophilic. Adaptation to growth on humans by most geophilic species resulted in diminished loss of sporulation, sexuality, and other soil-associated characteristics. The dermatophytes have the ability to invade keratinized tissue (skin, hair, and nails) but are usually restricted to the nonliving cornified layer of the epidermis because of their inability to penetrate viable tissue of an immunocompetent host. However, invasion does elicit a host response ranging from mild to severe. Acid proteinases, elastase, keratinases, and other proteinases reportedly act as virulence factors. The development of cell-mediated immunity correlated with delayed hypersensitivity and an inflammatory response is associated with clinical cure, whereas the lack of or a defective cell-mediated immunity predisposes the host to chronic or recurrent dermatophyte infection. Chronic dermatophytosis is mostly caused by Trichophyton rubrum, and there is some evidence that mannan produced by this fungus suppresses or diminishes the inflammatory response. Since dermatophytes cause a communicable disease, modes of transmission and control are discussed as well as a survey of recent trends in therapy. Collection of specimens, culture media, and tests for identification are also presented. Genetic studies have led to an understanding of incompatibility mechanisms, pleomorphism and variation, resistance to griseofulvin, and virulence. Molecular biology has contributed to our knowledge of the taxonomy and phylogenetic relationships of dermatophytes.