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Trichophyton rubrum (Castell.) Sabour. 1911

Brief Summary

    Brief Summary
    provided by EOL authors

    There are many strains of Trichophyton rubrum that have been described and mycologists disagree in the accuracy of many of these [1]. Two types that are commonly described are Trichophyton rubrum downy type and Trichophyton rubrum granular type [1]. Under the microscope the downy type types makes slender clavate (club-shaped) microconidia and does not make macroconidia [1]. Granular types in the other hand make a large number of clavate to pyriform (pear-shapee) microconidia and thin-walled, cigar-shaped macroconidia [1]. In order to accurately identify Trichophyton rubrum it is necessary a combination of macroscopic and microscopic characteristics since Trichophyton rubrum is a very flexible fungus and many characteristics are similar with other Trichophyton species [2].

    Brief Summary
    provided by EOL authors

    Trichophyton rubrum was first described in 1910 by Castellani A. in the 19th century [6]. It is the most common cause dermatophytosis, also known as ringworm and tinea [1]. Trichophyton rubrum is an obligate anthropophilic(can infect humans only) fungus that gets its energy from the breakdown of keratin on human surfaces [5][8]. Keratin is a fibrous protein in the epithelium (outermost layer) of animals which provides important structural and protective functions [9]. Nutrient acquisition is done through the breakdown of keratin by proteases (proteins that degrade other proteins) released from the fungus [3]. There is work being done to fully understand its life cycle. It is believed that is sexual reproduction state is similar to closely related species like Trichophyton mentagrophytes, Trichophyton ajelloiandMicrosporum canis (all whose sexual life cycle have been fully understood) but so far there is no concrete data to describe it [10]. Its asexual state has not been properly described either but oddly enough it is believed that it resembles more distant species like A. nidulunsorN. crassa. Dermatophytes, unlike most other fungi, can cause infections in individuals with competent immune systems and individuals seem to be long life carriers post infection. [3]. Trichophyton rubrum is most commonly found in moist areas of the human body where keratin is easily accessible like folds on the skin and under finger and toe nails [3]. Trichophyton rubrum is believed to have evolved in Southeast Asia in the 19th century but it is now found worldwide due to troops returning to their homes or refugees fleeing the country after the Vietnam War [2][7]. Proper identification for dermatophytes is very difficult and can take from 2 to 4 weeks [10]. It requires proper isolation of cultures and microcopy and there is always a risk of misidentification due to pleomorphic growth (change in morphology due to environmental stress) [10].

    Brief Summary
    provided by EOL authors

    Trichophyton rubrum (most commonly known as ringworm or tinea) is a keratinophilic (feeds on keratin) fungus that can only parasitize humans (obligate antropophile)[5][8]. It is believed to have evolved fairly recently and was first described in Southeast Asia in the 19th century[6][7]. This fungus is now endemic to every continent except for Antarctica and it accounts for more than half of all skin infections caused by fungi [4][5]. This makes this fungus not only economically important but also militarily important as it has been known to immobilize troops in various instances [3].

    Trichophyton rubrum produces club-shaped or pear-shaped microconidia (spore producing structure) and thin-wall cigar shaped macroconidia (larger spore producing structure) which are very similar to many other species in the same family [2]. This means that it is extremely hard to properly identify this organism. This augmented by the fact that even when properly grown and isolated, the fungus can change its shape in accordance with environmental stress, makes it almost impossible to identify by morphology alone [10].

    Even though Trichophyton rubrum accounts for more than half of all fungal skin infections and has been documented to have incapacitated military troops in two different occasions (Vietnam in the 1960s and Panama in the 1980s) very little is known about its life cycle[2][3]. Both sexual and asexual reproductive cycles are assumed to be like closely related organism but it is only from empirical evidence [2].

    Although Trichophyton rubrum is so ubiquitous and a very common cause for skin infections that can be very painful, it is known to have very low lethality [3]. In fact it has been reported to only cause death in immunocompromised patients and infants whose immune system are not fully developed yet, which is probably one of the reasons that there are no effective treatments that can address this problem [3].

    Brief Summary
    provided by EOL authors

    Even though Dermatophyte infections do not cause death most of the time, they are difficult to treat and can be extremely painful [4]. In one instance in the Mekong Delta in Vietnam in 1966-1969, 50% if the American troops in the region were put out of action by a Dermatophyte infection [3]. In another well documented incident 50% of American troops showed symptoms of infection after being deployed in the hot and humid climate of Panama in the 1980s [3]. 500 million dollars a year are spent worldwide in the treatment of Dermatophyte infections [4]. While this might seem like an enormous amount of money being spent in treatment for fungi that are most of the time non-lethal, it is important to take into account three factors. First is that due to the fact that the main source of nutrients of these fungi is keratin, almost any surface of the body can be colonized by Dermatophytes (including feet, torso, scalp and nails), second is that there are not any effective treatments to treat these infections, and third is that in many species (like Trichophyton rubrum) there is relapse after treatment [3]. Out of all the Dermatophyte infections the species Trichophyton rubrum is the most prevalent [5] which is probably due to the fact that Trichophyton rubrum is endemic to all continents except for Antarctica [4]. At the Canadian National Center 58% of Dermatophylic isolates were Trichophyton rubrum [5]. Trichophyton rubrum releases proteases that not only degrade proteins in epithelial surfaces but also help with the adhesion and sequential invasion of the host [3]. Once the host becomes infected the fungus causes itchy and flaky skin that is sometimes accompanied by redness and swelling [5]. Infections are characterized by what part of the body they are found. Currently there are six categories: Tinea pedis (feet), tinea cruris (proximal medial thights, preum and buttocks), tinea unguium (nails), tinea corporis (body), tinea barbae (beard) and tinea capitis (scalp) [5] (tinea corporis and tinea cruris are commonly known as ringworm). Different fungi can cause one or more of these six conditions and Trichophyton rubrum is known to cause all of them [5]. The most common form of transmission is through the feet as skin scales left in carpets or mats are excellent vectors for transmission and can survive for month or even year on these substrates [5]. The reason that skin scales are so infectious is that they contain hyphal elements of the fungi which are able to replicate and parasitize a new host [5].