Microsporum is known as a genus of individual species of fungi that belong to the dermatophytes as well as Fungi imperfecti and are taxonomic representatives of the true tubular fungi. The most important members of the genus include representatives Microsporum audouinii, canis and gypseum species, which live on the skin of animals and humans, as well as in the soil. Most species are considered human pathogens.
What is Microsporum?
Dermatophytes are filamentous fungi that can cause fungal disease. The disease they cause is also known as dermatophytosis or tinea. The so-called Microsporum corresponds to a genus of filamentous fungi from the non-taxonomic class Fungi imperfecti. Fungi imperfecti, also called imperfect fungi or deuteromycetes, belong to the higher fungi in the sense of tube, stand and yoke fungi. There is apparently no phase of sexual fertilization in their developmental cycle. Most species of microspores are also thought to be dermatophytes and are thus human pathogens. Taxonomically, the microspores are true tubular fungi or Pezizomycotina and fall under them in the class Eurotiomycetes. Their subclass corresponds to the Eurotiomycetidae. The higher order is Onygenales. The family of microspores is considered to be the family Arthrodermataceae. The macroconidia of the microspores are thin- to thick-walled and carry an ovoid or spindle shape. Their consistency is rough and they are divided into individual chambers in the form of septa, which sit on top of the hyphae individually. When infected, the fungi cause microsporiasis. This is a fungal disease of the skin, which belongs to the dermatomycoses and thus corresponds to a form of dermatophytosis. Typical representatives of Microsporum are Microsporum audouinii, canis and gypseum.
Occurrence, distribution, and characteristics
Microsporum canis is a parasite on the skin of cats and dogs. The fungus is transmitted to humans or other animals by zoonosis. In southern countries, approximately all stray animals are infected with the pathogen. The fungus forms cotton wool-like and limited colonies on culture media, which appear creamy-white to orange-yellowish. It has septate hyphae and smooth club-like microconidia in the macroscopic image. The individual macroconidia bear spindle shape and are up to 25 by 110 microns in size. They each bear up to 18 chambers, have knotted ends and rough walls. Microsporum gallinae is also a parasitic skin fungus that frequently causes dermatophytosis, especially in birds. As a zoonotic pathogen, it can also cause infections across species. This fungus forms slightly downy, velvety white colonies and shows septate hyphae under the microscope with round to pear-shaped microconidia to a size of up to eight by 50 micrometers. The microconidia show slight curvature and are equipped with fine spines at the ends. Another representative of Microsporum is the skin parasite Microsporum gypseum. It lives mainly geophilic and is transmitted through the soil. In humans, transmission leads to the picture of gardener’s microsporum, but horses and cats can also be carriers of the pathogen due to zoonosis. The fungus forms fluffy white colonies with septate hyphae and club-shaped microconidia up to 16 by 50 micrometers in size. The symmetrically arranged, rough and thin-walled microconidia are rounded at the ends. Humans become infected with Microsporum primarily through contact with contaminated animals, and less commonly through contact with soil. Smear infection from person to person is also possible. Fungi of the species reproduce purely vegetatively or by spores. These so-called conidia are formed in an asexual manner. For their growth, they obtain energy from the decomposition of carbohydrates and keratin, which they perform with the help of the enzyme keratinase.
Diseases and ailments
Microsporum has clinical pathogenic significance and is considered the causative agent of microsporiasis. These dermatophytoses of the skin manifest as cutaneous mycosis. Tinea corporis is characterized by red scaling efflorescences that start centrally and spread bit by bit to the periphery in the course of the infection. In addition, fungi of the species Microsporum often cause hair mycosis. This tinea capitis is mainly associated with Microsporum canis and causes the hair to become brittle. Animals in particular, but also humans, can be silent carriers of the infection.In this case, they do not suffer from any symptoms, but can nevertheless continue to transmit the fungus. Depending on the region of infestation, the physician takes examination material from the edge of the lesion or from hairs for the purpose of diagnostics. Pathogens are detected microscopically or in cultural cultivation, for example on Sabouraud agar. Different agents are prescribed to patients for local therapy of the infection. Fluconazole and itraconazole are considered particularly promising agents in the treatment of various fungal diseases of the skin and hair. Voriconazole is also particularly effective against dermatophytes. Alternatively or in combination, active ingredients such as terbinafine or triazoles can be used. However, this therapeutic step usually only takes place in the case of extremely severe infestation. Even more rarely, the doctor prescribes patients griseofulvin, which used to be used far more frequently for the treatment of fungal diseases. People are particularly often infected with the pathogens during a vacation in southern regions. This connection is mainly due to the high rate of infestation of strays there.
