Epidermophyton floccosum

Epidermophyton floccosum

Epidermophyton floccosum has a skin fungus of the (non- taxonomic ) group of dermatophytes a medically significant importance as it is a cause of fungal skin infections. He exclusively attacks humans ( anthropophil ); is affected mainly the skin ( dermatophytosis ), rarely the nails ( nail fungus ), but never the hair.

Macroscopic characteristics

Both on Sabouraud glucose agar ( alternatively Kimmig agar ), as well as on Mycosel agar dermatophyte grows medium fast, initially white. But after a few days of the thallus takes on its characteristic greenish-yellow ( " olive " ) staining. However, the range of variation is surprisingly large, so that even violet or pink colored isolates are possible. Colonies are usually flat with central, button-like survey and traversed by radial furrows and wrinkles. After 10 days at 30 ° C, the colony having a diameter of 10-25 mm. Typically, the onset already after three weeks called pleomorphism, what actually ' the diversity ' means. Here it is recognizable by the white, cotton -like Luftmyzelflöckchen (see mycelium ) in the midst of the colonies. With increasing age, and after a few subcultures of the fungus is completely pleomorphic and only consists of white, wattigem and so-called sterile mycelium. The primary culture underside is colorless, later yellow- brown and furrowed.

Microscopic characteristics

In the microscopic picture, numerous club-shaped, smooth and thin-walled macroconidia show with 2-8 chambers individually laterally sit at the septate hyphae or arranged terminal to 2-5 in clusters. You can be 7-12 microns wide and 20-40 microns long. In contrast to the genera Trichophyton and Microsporum no microconidia are formed. Depending on the culture age are increasingly intercalary and terminal to see 20 microns large chlamydospores.

Physiological characteristics

The growth optimum is at 28 ° C. But the fungus grows well at 37 ° C. Unlike other dermatophytes can not infect E. floccosum hair. Vitamin supplements to the medium have no significant impact and can therefore be neglected. The urease is common after 7 days at 25 ° C positive but not always reliable. On BCP ( bromocresol purple )-lactic glucose agar, the indicator turns yellow in contrast to Trichophyton rubrum strains pigmented purple. Stunted, pleomorphic cultures can be prepared by inoculation on salt- containing agar plates, which 3% or even 5 % sodium chloride ( NaCl) is added to bring them back to their original, flat, greenish-yellow and makrokonidienhaltige habit. This is also a differentiator to other dermatophytes, which either did not grow under these conditions or remain pleomorphic.

Clinical Significance

The fungus is spread from person to person, often indirectly through shower rooms, bathrooms, towels, shoes and clothing (underwear and socks ). Experimental infections in experimental animals have been unsuccessful. In man the infection occurs most commonly in the groin and legs as tinea cruris et ulcers, but also in the face ( tinea facial artery ), neck, back, abdomen as tinea corporis, arms, back of the hands, palms and fingers intervals as tinea manus on soles and toe webs as tinea pedis, and much less frequently in the nails as tinea unguium or onychomycosis. Tinea corporis is characterized by reddening and pustelbildende skin disorders with ring - shaped beam to spread.

Study material and method of determination

It such materials should be used that can affect the fungus, ie skin and Nagelschüppchen, but no hair and hair roots. From the study material, the fungal culture will be made to at least two different culture media in addition to the direct preparation. Should be used in 20 percent potassium hydroxide solution for digestion for the direct preparation preferably Calcofluor. In the positive case can be seen infinite chains of thick-walled, green glowing, not severely swollen, intercalary chlamydospores using a fluorescence microscope at 100-fold initially, then 400 - fold magnification. Possibly because some strains of E. floccosum by cycloheximide could be inhibited in the soil, in addition always at least a breeding ground should be used without cycloheximide.

Assessment

Epidermophyton floccosum is in any case of pathogens, which occurs in Central Europe compared to other dermatophytes fourth most. Any evidence from patient material - Skin and Nägelschüppchen - is to be regarded as requiring treatment findings. The treatment is done externally with antifungal creams and solutions, infection of the nails by systemically active antifungal agents in tablet or capsule form, including terbinafine or itraconazole.