CLINICAL MICROBIOLOGY REVIEWS, Apr. 1995, p. 240–259
`0893-8512/95/$04.00⫹0
`Copyright 䉷 1995, American Society for Microbiology
`
`Vol. 8, No. 2
`
`The Dermatophytes
`IRENE WEITZMAN1* AND RICHARD C. SUMMERBELL2
`Clinical Microbiology Service, Columbia Presbyterian Medical Center, New York, New York 10032-3784,1 and
`Mycology Laboratory, Laboratory Services Branch, Ontario Ministry of Health, Toronto, Ontario M5W 1R5, Canada2
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`INTRODUCTION .......................................................................................................................................................240
`HISTORICAL REVIEW.............................................................................................................................................241
`ETIOLOGIC AGENTS...............................................................................................................................................241
`Anamorphs...............................................................................................................................................................241
`Epidermophyton spp. ...........................................................................................................................................241
`Microsporum spp. ................................................................................................................................................241
`Trichophyton spp. ................................................................................................................................................241
`Teleomorphs ............................................................................................................................................................242
`EPIDEMIOLOGY AND ECOLOGY ........................................................................................................................242
`CLINICAL MANIFESTATIONS ..............................................................................................................................244
`Tinea Barbae ...........................................................................................................................................................244
`Tinea Capitis ...........................................................................................................................................................244
`Tinea Corporis ........................................................................................................................................................244
`Tinea Cruris (‘‘Jock Itch’’)....................................................................................................................................244
`Tinea Favosa............................................................................................................................................................245
`Tinea Imbricata.......................................................................................................................................................245
`Tinea Manuum........................................................................................................................................................245
`Tinea Pedis (‘‘Athlete’s Foot’’)..............................................................................................................................245
`Tinea Unguium........................................................................................................................................................245
`LABORATORY DIAGNOSIS....................................................................................................................................245
`Collection and Transport of Specimens ..............................................................................................................245
`Microscopic Examination and Culture................................................................................................................245
`Identification Characters and Diagnostic Media ...............................................................................................246
`IMMUNOLOGY..........................................................................................................................................................247
`PREVENTION AND CONTROL..............................................................................................................................248
`PHYSIOLOGY ............................................................................................................................................................249
`HISTOPATHOLOGY .................................................................................................................................................250
`THERAPY ....................................................................................................................................................................251
`Tinea Capitis ...........................................................................................................................................................251
`Tinea Barbae ...........................................................................................................................................................251
`Tinea Corporis ........................................................................................................................................................251
`Tinea Cruris ............................................................................................................................................................251
`Tinea Pedis ..............................................................................................................................................................251
`Tinea Unguium........................................................................................................................................................252
`GENETICS ..................................................................................................................................................................252
`Heterothallism.........................................................................................................................................................252
`Pleomorphism..........................................................................................................................................................252
`Virulence ..................................................................................................................................................................252
`Griseofulvin Resistance..........................................................................................................................................252
`Pigmentation in A. benhamiae ...............................................................................................................................253
`MOLECULAR BIOLOGY .........................................................................................................................................253
`FUTURE PROSPECTS..............................................................................................................................................254
`ACKNOWLEDGMENT..............................................................................................................................................254
`REFERENCES ............................................................................................................................................................254
`
`INTRODUCTION
`
`The dermatophytes are a group of closely related fungi that
`have the capacity to invade keratinized tissue (skin, hair, and
`nails) of humans and other animals to produce an infection,
`
`* Corresponding author. Phone: (212) 305-9377. Fax: (212) 305-
`8971.
`
`240
`
`dermatophytosis, commonly referred to as ringworm. Infection
`is generally cutaneous and restricted to the nonliving cornified
`layers because of the inability of the fungi to penetrate the
`deeper tissues or organs of immunocompetent hosts (57, 140).
`Reactions to a dermatophyte infection may range from mild to
`severe as a consequence of the host’s reactions to the meta-
`bolic products of the fungus, the virulence of the infecting
`strain or species, the anatomic location of the infection, and
`local environmental factors.
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`VOL. 8, 1995
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`THE DERMATOPHYTES
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`241
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`HISTORICAL REVIEW
`
`Historically, medical mycology, specifically relating to hu-
`man disease, began with the discovery of the fungal etiology of
`favus and centered around three European physicians in the
`mid-19th century: Robert Remak, Johann L. Scho¨nlein, and
`David Gruby. Details regarding their lives, specific achieve-
`ments, and historical background may be found in several
`excellent reviews (4, 10, 141, 217, 283).
`According to Seeliger (217), Remak in 1835 first observed
`peculiar microscopic structures appearing as rods and buds in
`crusts from favic lesions. He never published his observations,
`but he permitted those observations to be cited in a doctoral
`dissertation by Xavier Hube in 1837. Remak claimed that he
`did not recognize the structures as fungal (194) and credited
`this recognition to Scho¨nlein, who described their mycotic na-
`ture in 1839 (214). However, Remak established that the eti-
`ologic agent of favus was infectious, cultured it on apple slices,
`and validly described it as Achorion schoenleinii, in honor of his
`mentor and his initial discovery (195).
`The real founder of dermatomycology was David Gruby on
`the basis of his discoveries during 1841 to 1844, his communi-
`cations to the French Academy of Science, and his publications
`during this period (86–89). Independently, and unaware of the
`work of Remak and Scho¨nlein, he described the causative
`agent of favus, both clinically and in microscopic details of the
`crusts, and established the contagious nature of the disease
`(86, 87). He also described ectothrix invasion of the beard and
`scalp, naming the etiologic agent of the latter Microsporum
`(referring to the small spores around the hair shaft) audouinii
`(88), and described endothrix hair invasion by Herpes (Tricho-
`phyton) tonsurans (89). In addition to his observations on der-
`matophytes, he also described the clinical and microscopic
`appearance of thrush in children.
`Raimond Sabouraud, one of the best known and most in-
`fluential of the early medical mycologists, began his scientific
`studies of the dermatophytes around 1890, culminating in the
`publication of his classic volume, Les Teignes, in 1910 (210).
`Sabouraud’s contributions included his studies on the taxon-
`omy, morphology, and methods of culturing the dermatophytes
`and the therapy of the dermatophytoses. He classified the
`dermatophytes into four genera, Achorion, Epidermophyton,
`Microsporum, and Trichophyton, primarily on the basis of the
`clinical aspects of the disease, combined with cultural and
`microscopic observations. The medium that he developed is in
`use today for culturing fungi (although the ingredients are
`modified) and is named in his honor, Sabouraud glucose (dex-
`trose) agar (177). Sabouraud’s treatment of tinea capitis by a
`one-dose, single-point roentgenologic epilation achieved cures
`in 3 months as opposed to the then current therapy of manual
`epilation and topical application of medications (153).
`In 1934, Chester Emmons (60) modernized the taxonomic
`scheme of Sabouraud and others and established the current
`classification of the dermatophytes on the bases of spore mor-
`phology and accessory organs. He eliminated the genus Acho-
`rion and recognized only the three genera Microsporum,
`Trichophyton, and Epidermophyton on the basis of mycological
`principles.
`Nutritional and physiological studies of the dermatophytes
`pioneered at Columbia University by Rhoda Benham and
`Margarita Silva (25, 223) and at the Center for Disease Con-
`trol, in Georgia, by Libero Ajello, Lucille K. Georg, and co-
`workers (8, 69, 74, 242) simplified the identification of der-
`matophytes and led to reduction of the number of species and
`varieties.
`The discovery of the teleomorphs (perfect or sexual state) of
`
`Trichophyton (Keratinomyces) ajelloi in 1959 by Dawson and
`Gentles (52), using the hair bait technique of Vanbreuseghem
`(255), led to the rapid discoveries of the teleomorphs of many
`dermatophytes and related keratinophilic fungi. Griffin in 1960
`(84) and Stockdale in 1961 (231) and 1963 (232) independently
`obtained the teleomorphs of the Microsporum gypseum com-
`plex, thereby vindicating Nannizzi’s original observation.
`The discovery of sexual reproduction in the dermatophytes
`opened the door to classical genetic studies with these fungi,
`e.g., determining the cause of pleomorphism (269) and clari-
`fying the taxonomy and understanding of the incompatibility
`systems operating in these fungi (268).
`The successful oral therapy with griseofulvin of experimental
`dermatophytosis in guinea pigs reported by Gentles in 1958
`(75) revolutionized the therapy of dermatophytosis and initi-
`ated the first major change in the therapy of tinea capitis since
`the work of Sabouraud.
`
`ETIOLOGIC AGENTS
`
`Anamorphs
`The etiologic agents of the dermatophytoses are classified in
`three anamorphic (asexual or imperfect) genera, Epidermophy-
`ton, Microsporum, and Trichophyton, of anamorphic class Hy-
`phomycetes of the Deuteromycota (Fungi Imperfecti). The
`descriptions of the genera essentially follow the classification
`scheme of Emmons (60) on the bases of conidial morphology
`and formation of conidia and are updated following the dis-
`covery of new species (2, 5, 165). The genera and their descrip-
`tions are as follows.
`Epidermophyton spp. The type species is Epidermophyton
`floccosum. The macroconidia are broadly clavate with typically
`smooth, thin to moderately thick walls and one to nine septa,
`20 to 60 by 4 to 13 ␮m in size. They are usually abundant and
`borne singly or in clusters. Microconidia are absent. This genus
`has only two known species to date, and only E. floccosum is
`pathogenic.
`Microsporum spp. The type species is Microsporum audoui-
`nii. Macroconidia are characterized by the presence of rough
`walls which may be asperulate, echinulate, or verrucose. Orig-
`inally, the macroconidia were described by Emmons as spindle
`shaped or fusiform, but the discovery of new species extended
`the range from obovate (egg shaped) as in Microsporum nanum
`(67) to cylindrofusiform as in Microsporum vanbreuseghemii
`(73). The macroconidia may have thin, moderately thick to
`thick walls and 1 to 15 septa and range in size from 6 to 160 by
`6 to 25 ␮m. Microconidia are sessile or stalked and clavate and
`usually arranged singly along the hyphae or in racemes as in
`Microsporum racemosum, a rare pathogen (31).
`Trichophyton spp. The type species is Trichophyton ton-
`surans. Macroconidia, when present, have smooth, usually thin
`walls and one to 12 septa, are borne singly or in clusters, and
`may be elongate and pencil shaped, clavate, fusiform, or cylin-
`drical. They range in size from 8 to 86 by 4 to 14 ␮m. Micro-
`conidia, usually more abundant than macroconidia, may be
`globose, pyriform or clavate, or sessile or stalked, and are
`borne singly along the sides of the hyphae or in grape-like
`clusters.
`The anamorphic species of the dermatophytes are listed in
`Table 1. Descriptions of the species and related keratinophilic
`fungi may be found in several publications (134, 153, 193, 200,
`270, 274).
`Since the classification of the dermatophytes by Emmons
`(60), as a result of the discovery of new species and variants,
`the rigid morphological distinction among the three genera has
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`242
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`WEITZMAN AND SUMMERBELL
`
`CLIN. MICROBIOL. REV.
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`TABLE 1. Anamorph genera and species of dermatophytes
`
`Epidermophyton Sabouraud 1907
`E. floccosum (Harz) Langeron et Milochevitch 1930
`
`Microsporum Gruby 1843
`M. audouinii Gruby 1843
`M. canis Bodin 1902
`M. equinum (Delacroix et Bodin) Guegue´n 1904
`M. ferrugineum Ota 1921
`M. fulvum Uriburu 1909
`M. gallinae (Megnin) Grigorakis 1929
`M. gypseum (Bodin) Guiart et Grigorakis 1928
`M. nanum Fuentes 1956
`M. persicolor (Sabouraud) Guiart et Grigorakis 1928
`M. praecox Rivalier, ex Padhye, Ajello et McGinnis 1987
`M. racemosum Borelli 1965
`M. vanbreuseghemii Georg, Ajello, Friedman et Brinkman 1962
`
`Trichophyton Malmsten 1845
`T. concentricum Blanchard 1895
`T. equinum (Matruchot et Dassonville) Gedoelst 1902
`T. gourvilii Catanei 1933
`T. kanei Summerbell 1989a
`T. megninii Blanchard 1896
`T. mentagrophytes (Robin) Blanchard 1896
`T. raubitschekii Kane, Salkin, Weitzman, Smitka 1981a
`T. rubrum (Castellani) Sabouraud 1911
`T. schoenleinii (Lebert) Langeron et Milochevitch 1930
`T. simii (Pinoy) Stockdale, Mackenzie et Austwick 1965
`T. soudanense Joyeux 1912
`T. tonsurans Malmsten 1845
`T. verrucosum Bodin 1902
`T. violaceum Bodin 1902
`T. yaoundei Cochet et Doby Dubois 1957 (not validly published)
`
`a Some mycologists consider T. kanei and T. raubitschekii to fall within the
`circumscription of T. rubrum.
`
`become a morphological continuum based on overlapping
`characteristics; e.g., Trichophyton kanei (238), Trichophyton
`longifusum (65), and a variant of T. tonsurans (183) lack mi-
`croconidia, and therefore are more suggestive of the genus
`Epidermophyton, whereas isolates of Microsporum spp. produc-
`ing smooth-walled macronidia are more suggestive of Tricho-
`phyton spp. (258, 275).
`
`Teleomorphs
`
`Some dermatophytes, mostly the zoophilic and geophilic
`species of Microsporum and Trichophyton, are also capable of
`reproducing sexually and producing ascomata with asci and
`ascospores. These species are classified in the teleomorphic
`genus Arthroderma (271), family Arthrodermataceae of the
`Onygenales (45), phylum Ascomycota. Previously, the teleo-
`morphs of the sexually reproducing Microsporum and Tricho-
`phyton species and related keratinophilic fungi had been clas-
`sified in the genera Nannizzia and Arthroderma, respectively
`(5). However, on the basis of a careful evaluation of the mor-
`phological characteristics used to define these two genera,
`Weitzman et al. (271) concluded that the species making up
`these genera represented a continuum and that their minor
`differences did not merit maintaining them in two separate
`genera. Nannizzia and Arthroderma are considered to be con-
`generic, with Arthroderma having taxonomic priority.
`The teleomorph-anamorph states of the dermatophytes and
`related species are listed in Table 2.
`
`TABLE 2. Teleomorph-anamorph state of dermatophytes
`Teleomorph (reference)
`Anamorph
`Arthroderma..........................................Microsporum, Trichophyton
`A. benhamiae (7) .................................T. mentagrophytesa
`A. fulvum (232, 271)............................M. fulvumb
`A. grubyi (73, 271) ...............................M. vanbreuseghemii
`A. gypseum (231, 232, 271).................M. gypseumb
`A. incurvatum (231, 232, 271) ............M. gypseumb
`A. obtusum (51, 271)...........................M. nanum
`A. otae (94, 271) ..................................M. canis var. canis, M. canis var.
`distortum
`A. persicolor (233, 271) .......................M. persicolor
`A. simii (236)........................................T. simii
`A. racemosum (209, 271) ....................M. racemosum
`A. vanbreuseghemii (245) ....................T. mentagrophytesa
`
`a,b These anamorph species are considered complexes, each of which includes
`more than one teleomorph.
`
`EPIDEMIOLOGY AND ECOLOGY
`
`Dermatophytes are among the few fungi causing communi-
`cable disease, that is, diseases acquired from infected animals
`or birds or from the fomites they have engendered. All but one
`of the species known to cause disease primarily affect mam-
`mals. The exception, Microsporum gallinae, is primarily estab-
`lished in gallinaceous fowl. Apart from those species usually
`associated with disease, transitional species exist which appear
`to be primarily saprobic organisms occasionally or rarely caus-
`ing infection. Finally, some Trichophyton, Epidermophyton, and
`Microsporum species closely related to the dermatophytes ap-
`pear to be exclusively saprobic or nearly so. The members of
`these three genera have no collective designation. The term
`dermatophytes should be restricted to designate infectious or-
`ganisms (3) and will be referred to below as dermatophytes and
`their congeners. Closely biologically related organisms not in-
`cluded in this group include Chrysosporium species with teleo-
`morphs in the genus Arthroderma.
`Dermatophytes and their congeners have long been divided
`into anthropophilic, zoophilic, and geophilic species on the
`basis of their primary habitat associations (1, 72). Anthropo-
`philic dermatophytes are primarily associated with humans and
`rarely infect other animals (166). Zoophilic dermatophytes
`usually infect animals or are associated with animals but occa-
`sionally infect humans. Geophilic dermatophytes are primarily
`associated with keratinous materials such as hair, feathers,
`hooves, and horns after these materials have been dissociated
`from living animals and are in the process of decomposition.
`These species may cause human and animal infection. Geo-
`philic species are thought to have been ancestral to the patho-
`genic dermatophytes, preadapted to cutaneous pathogenesis
`by their ability to decompose keratin and their consequent
`close association with animals living in hair and feather-lined
`nests in contact with soil (41).
`The distinction between geophilic and zoophilic dermato-
`phytes is based on detailed ecological analysis and may not be
`obvious in small-scale studies. Certain species known to be
`zoophilic may be isolated more often from soil and from fur of
`apparently healthy animals (62, 179) than from animals with
`frank disease. Many infections by zoophilic dermatophytes ap-
`pear to be acquired indirectly from keratinous fomites, often
`deriving from apparently healthy animal carriers (59). Poten-
`tially infectious geophilic dermatophytes such as members of
`the M. gypseum complex, growing on similar keratinous debris,
`overlap in ecology with these zoophiles. They differ mainly by
`their greater persistence in soil and are found regularly in
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`THE DERMATOPHYTES
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`TABLE 3. Current synopsis of dermatophyte species and congeners: ecological classification, host preference, and endemicity
`
`Anthrophilic species (area of endemicity)
`
`Zoophilic species (typical host)
`
`Geophilic species
`
`M. canis (cat, dog)
`M. equinum (horse)
`M. gallinae (fowl)
`M. persicolor (vole)
`
`T. equinum (horse)
`T. mentagrophytes (two sibling species and
`variants; rodents, rabbit, hedgehog)
`T. sarkisorii (Bactrian camel)
`T. simii (monkey, fowl)
`T. verrucosum (cattle, sheep, dromedary)
`
`E. floccosum
`M. audouinii (Africa)
`M. ferrugineum (East Asia, East Europe)
`T. concentricum (Southeast Asia, Melanesia,
`Amazon area, Central America, Mexico)
`T. gourvilii (Central Africa)
`T. kanei
`
`T. megninii (Portugal, Sardinia)
`T. mentagrophytes (complex of two species)
`T. raubitschekii (Asia, Africa, Mediterranean)
`T. rubrum
`T. schoenleinii
`T. soudanense (Subsaharan Africa)
`T. tonsurans
`T. violaceum (North Africa, Middle East,
`Mediterranean)
`T. yaoundei (Central Africa)
`
`E. stockdaleae
`M. amazonicum
`Microsporum anamorph of A. cookiellum
`M. boullardii
`
`M. cookei
`M. gypseum (complex of three species)
`
`M. nanum
`M. praecox
`M. racemosum
`M. ripariae
`M. vanbreuseghemii
`T. ajelloi
`T. flavescens
`T. gloriae, T. longifusum
`
`T. phaseoliforme,
`T. terrestre (complex of three species),
`T. vanbreuseghemii
`
`habitats not strongly modified by the constant presence of
`animal associates. A synopsis of dermatophyte species and
`congeners, ecological and host preferences, and endemicity
`may be found in Table 3.
`Rippon (200) has pointed out a correspondence between
`soil association and conidial production in dermatophytes: the
`less significant the growth on dissociated keratin in the ecology
`of a dermatophyte, the less likely is the dermatophyte to pro-
`duce conidia abundantly. Soil association also tends to corre-
`late with the ability to form heterothallic teleomorphs in na-
`ture (153), an ability not
`found in most anthropophilic
`dermatophytes and some zoophiles. Many anthropophilic and
`certain zoophilic species appear to consist predominantly or
`exclusively of isolates of a single mating type, as determined by
`the induction of infertile ascomata with Arthroderma simii mat-
`ing type testers (234). Summerbell in reference 248 has pointed
`out that burrowing and denning animals tend to be associated
`with dermatophytes possessing a full roster of soil association
`characters, including conidial abundance and dimorphism, het-
`erothallic mating, osmotolerance, and the possession of typical
`arthropod predation deterrent structures such as conidial or-
`namentation, helical setae (spirals), and the rigid peridial net-
`works found in gymnothecia and pseudogymnothecia. To these
`soil association characters can be added vitamin and amino
`acid autotrophy, the elaboration of a urease enzyme, and the
`formation of perforating organs in dissociated hair. Dermato-
`phytes primarily associated with humans or with nonburrow-
`ing, nondenning animals such as ungulates and equines tend to
`lack some or all of these characters. Several specialized an-
`thropophilic species (e.g., Trichophyton concentricum and Mi-
`crosporum ferrugineum) consist of highly morphologically sim-
`plified, asexual isolates with little or no ability to produce
`conidia.
`The dermatophyte structure most commonly associated with
`contagion, especially in the poorly conidial anthropophilic der-
`matophytes, is the oblong to rounded, persistent ‘‘spore,’’ ‘‘ar-
`throconidium,’’ or ‘‘chlamydospore’’ found within or attached
`to the exterior of infected hairs and within skin scales. These
`structures, particularly in certain species, may persist for years
`in the environment (200, 220) and are highly heat resistant
`(222), particularly when embedded in hair or skin scales (230).
`In some anthropophilic species studied in detail, arthroconidia
`
`have a tendency to adhere in vitro to corneocytes derived from
`particular body sites (9, 284). It is possible that they may
`dissociate from skin cells in the environment and come in
`contact with new potential hosts as disseminated arthro-
`conidia. Their persistence as an environmental source of con-
`tagion may lead to recurrent outbreaks of dermatophytosis in
`individuals and in institutions (128, 162). According to Rippon
`(200), the arthroconidia of T. rubrum do not survive as long as
`do those of other species, e.g., E. floccosum. The transition
`from potentially sexual to asexual life histories in the non-soil-
`associated dermatophytes appears to have led to adaptive ra-
`diation, at least in the anthropophilic dermatophytes (248). By
`most estimates, approximately two-thirds of the recognized
`dermatophyte species primarily associated with mammalian
`pathogenesis are anthropophiles (248). Within the anthropo-
`philes, polymorphous morphological variation is common, and
`numerous atypical and variant types are recognized (133, 193,
`279), probably indicating further genetic drift. Allopatric spe-
`ciation appears to have been common in anthropophilic der-
`matophytes but rare in zoophiles, and several anthropophilic
`species have well-defined areas of endemicity (200) (Table 3)
`while others, such as T. rubrum and T. tonsurans, are now
`cosmopolitan but appear to have had a more restricted distri-
`bution in the past, having been transported widely as a result of
`human migration (the anthropophiles travel with their human
`hosts) (200). Also, spatial and ecological sympatric isolation
`appears to have been a predisposer to speciation in the an-
`thropophiles: human-associated dermatophytes, unlike zoo-
`philes, often have marked affinities for particular body sites.
`Most recognized asexual anthropophilic dermatophyte species
`are distinctive in morphology, physiology, and body site pref-
`erence (127).
`Recognition of dermatophyte taxa is clinically relevant. The
`need for species identification of dermatophytes in clinical
`settings is often related to epidemiological concerns. Especially
`relevant is the identification of dermatophytes that (i) may
`have animal carriers; (ii) are linked to recurrent institutional or
`family outbreaks, such as T. tonsurans and Trichophyton viola-
`ceum (17, 128, 146, 147, 162, 228); (iii) may cause rapidly
`progressing epidemics, such as M. audouinii and T. tonsurans
`(34); and (iv) are geographically endemic, reflecting exposure
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`CLIN. MICROBIOL. REV.
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`during travel or residence in the area of endemicity or contact
`with a person with such a history (23, 261).
`Epidemiology is important in infection control and public
`health issues related to the different types of dermatophytosis.
`In tinea capitis, the predominant agents in North America are
`T. tonsurans and Microsporum canis. The former is usually
`acquired from infected humans or their fomites and has caused
`a progressive, continent-wide epidemic now of some 40 years
`in duration (34, 70, 200). Urban areas and their communities
`of minorities have been particularly strongly affected (34). M.
`canis is usually acquired from infected cats or dogs, although
`limited human-to-human transfer leading to outbreaks can
`occur (219, 226). It is the predominant agent of tinea capitis in
`rural areas and in some parts of Europe, the eastern Mediter-
`ranean, and South America (12, 38, 221, 260).
`Tinea capitis in general is a condition most commonly seen
`in children (200). In tinea capitis caused by T. tonsurans, how-
`ever, a proportion of sufferers become long-term carriers of a
`subclinical scalp infection and may intermittently shed viable
`inoculum for decades (22, 102, 128, 190). When encountered in
`symptomatic adults, T. tonsurans is more frequently seen as an
`agent of tinea corporis (34), and other infections, such as tinea
`manuum and onychomycosis, occur uncommonly. Similar pat-
`terns of age and body site preferences are found in other more
`geographically concentrated agents of endothrix tinea capitis
`such as T. violaceum (216). Tinea corporis caused by T. ton-
`surans and other agents of endothrix tinea capitis may be more
`common in persons, particularly women, in close contact with
`children than among other adults. In institutional outbreaks,
`staff may transmit the fungus among immobile patients (128,
`219). Contact sports may distribute the disease among adoles-
`cents and young adults (228). Among children, T. tonsurans is
`transmitted primarily by the sharing of combs, hats, bedding,
`and other materials contacting the scalp. Its environmental
`persistence on these fomites is noteworthy (128, 162).
`Zoophilic and geophilic dermatophytes in general tend to
`form lesions that are more inflammatory than those formed by
`anthropophilic dermatophytes but are also more likely to re-
`solve spontaneously (200). This pattern is seen in tinea capitis
`caused by M. canis (144, 145, 200). The closely related an-
`thropophile M. audouinii, once common in North America but
`now mainly restricted to parts of Africa and Asia (200), ap-
`pears particularly specialized as an agent of juvenile tinea
`capitis (200). Adult infections are rare, and spontaneous res-
`olution usually occurs upon attainment of puberty (144).
`Tinea other than tinea capitis, when caused by anthropo-
`philic fungi, tends to be associated with adults and adolescents,
`although infection of children may occur. Trichophyton rubrum,
`E. floccosum, and the anthropophilic Trichophyton mentagro-
`phytes (i.e., cottony and velvety forms [124, 133] known as T.
`mentagrophytes var. interdigitale) show a common pattern of
`association with tinea corporis, tinea cruris, and tinea pedis
`(61). In addition, T. rubrum and T. mentagrophytes are associ-
`ated with tinea manuum and onychomycosis (221, 239). It is
`likely that exposure to these dermatophytes is a common oc-
`currence. Although the ecological and host factors involved in
`developing symptomatic infection are poorly known, known
`risk factors include foot dampness and abrasion combined with
`likely exposure to high fungal inocu