Generating and Testing Molecular Hypotheses in the Dermatophytes

Abstract

4Dermatophytes are the most common cause of fungal infections worldwide, impacting millions of individuals annually. In the United States alone, this translates into an economic impact on the health care system estimated to exceed $400 million a year for treatment alone (8,46). A recent survey conducted in 16 European countries has shown that more than one-third (35 to 40%) of the 90,000 participants were suffering with a fungal foot disease, mainly caused by dermatophytes (4). In a recent study, 22 to 50% of children in a U.S. day care center exhibited symptoms of dermatophytic scalp infections (2). Despite the prominence of dermatophyte infections and their resulting socioeconomic consequences, the research and medical communities lack a sophisticated understanding of these organisms' biology. Consequently, effective preventatives and therapeutics are lacking. These deficiencies are in large part due to the lack of genetic tools available for the study of these fungi and their host specificities. Several research efforts are now poised to produce genomic and molecular resources that will enable the molecular characterization of dermatophytes. These resources will soon be available for use by the larger research community to address many questions about the biology and pathogenesis of dermatophytes. This review will elaborate on the current status of these resources and their importance to the study of the dermatophytes. DERMATOPHYTE BIOLOGY AND DISEASEDisease. Tinea is a fungal infection of the skin, hair, or nails (reviewed in reference 34). The phrase is made specific by the addition of another term referring to a specific body location. Thus, the term "tinea pedis" refers to a fungal infection of the feet. Other tinea infections include tinea capitis (scalp or head), tinea corporis (body or trunk), and tinea unguium (nails, also known as onychomycosis). These terms do not indicate the infecting organism but the type of infection and the body location. Tinea infections are usually localized to the surface and are rarely systemic or disseminated.Fungal infections can be asymptomatic, they can be acute and severe, associated with inflammation, or they can be chronic (most common) (34). Tinea pedis usually occurs in the toe webs, with considerable scaling, fissuring, maceration, and erythema, accompanied by severe itching or burning. Tinea pedis can also localize to the sole of the foot, extending up the sides of the foot. The destruction of the skin barrier can result in bacterial superinfection. Nail infections are associated with thickening, discoloration, and pain. Scalp infections can cause irreversible hair loss.Organisms. All of the dermatophytes are ascomycetous molds, members of the class Euascomycetes that also includes Aspergillus species and the dimorphic fungi ( Fig. 1) (34). The dermatophytes are classified into three genera: Trichophyton, Microsporum, and Epidermophton. As can be seen in Fig. 2, the dermatophytes are a monophyletic clade, although the assigned genus designations within the clade ...

Dermatófitos: interação patógeno-hospedeiro e resistência a antifúngicos

“…Infection models used in molecular studies about host-dermatophyte interactions are limited, and evaluation of the infection in vivo is restricted to zoophilic species, since spontaneous cure or even absence of colonization by anthropophilic species are known to occur. 1 An alternative has been the use of culture media containing molecules of the host's microenvironment, such as keratin and other proteins, delineating the profile of gene and protein expression of T. rubrum in the use of these molecules as a source of nutrients. 35 These research studies have contributed to a greater understanding of the molecular strategies of dermatophytes as they use the host's molecules to survive.…”

“…So far, about 30 species of dermatophytes have been identified among human pathogens. 1 The transmission of dermatophytoses or tineas occurs by direct contact with infected animals and humans or by indirect contact with contaminated fomites. The clinical forms vary according to the etiologic agent (species) and the anatomical site involved.…”

Differential gene expression in the pathogenic dermatophyte Arthroderma benhamiae in vitro versus during infection

“…Although millions of individuals suffer from dermatophytoses, which in many cases are long-lasting and difficult to cure, little is known of the biology and pathogenicity of these microorganisms (Vermout et al, 2008;White et al, 2008). During infection, dermatophytes exclusively invade and multiply within the epidermal stratum corneum, nails or hair, a characteristic which is attributed to their extraordinary ability to degrade insoluble keratin into oligopeptides and amino acids.…”

Fungi on the Skin: Dermatophytes and Malassezia

“…There are three types of dermatophytes, unrelated to the three genera (White et al 2008). Some dermatophyte species have only been found on humans and are assumed to be human-specific.…”

“…Dermatophytes are a group of pathogenic fungi that cause mostly superficial diseases on humans and other mammals (Kwon-Chung and Bennett 1992; White et al 2008;Achterman and White 2012a,b). The diseases that result from a dermatophyte infection are known as tineas.…”