Mycoses B35-B49

Infectious diseases caused by parasitic fungi.

A distinction is made (see Table 1):

• Dermatomycoses (mycoses of the skin)
  • dermatophytoses
  • yeast infections of the skin
  • Mould infections of the skin
• Deep mycoses
• System mycoses.

• Pathogen detection (here especially for dermatomycoses; see also mycology examination methods):
  • Potassium hydroxide native preparation: Skin scales are dissolved in 20% potassium hydroxide solution. The microscopic picture shows the fungal filaments without special staining. Indication of fungal infection, but not species or even group affiliation (dermatophytes, yeasts, moulds = DHS system).
  • Other st ains: Certain stains (Congo Red, Methylene Blue, Chlorazol Black) make fungi stand out particularly well against skin scales. Native preparations of Pityriasis versicolor are particularly suitable for staining according to Parker (drop equal volumes of blue ink and KOH onto the preparation). The colour is immediately taken up by the Malassezia spp!
  • Periodic acid-Schiff staining (PAS) in the histological preparation: In this highly sensitive histological procedure, fungal filaments and spores stain red. A differentiation of mould, dermatophyte mycelium and pseudomycelium of pathogenic yeasts is not possible by this optical method.
  • Fluorescence microscopy: The microscopic diagnosis of cala eyes is much more successful by using much more sensitive fluorescence microscopic methods with optical brighteners from the group of diaminostilbenes(Calcofluor white, Blankophor). These dyes specifically attach to the chitin of the fungal cell wall. Human keratin is only weakly stained (caution: cellulose, e.g. cotton threads, also fluoresce).
  • Wood-lamp: Greenish fluorescence, especially used for microsporiasis, favus, tinea inguinalis.
  • Culture (gold standard): On special culture media (e.g. Sabouraud glucose and Kimmig agar) dermatophytes grow within 1-4 weeks, moulds within 1-2 weeks and yeasts within 3-4 days. By growth form and colour of the culture a tentative diagnosis is possible.
  • Microculture: Precise microscopic differentiation by micro- and macroconidia, chlamydospores, shape and arrangement of blastospores and pseudomycelia.
  • Molecular diagnostics: PCR-based genetic identification method. Advantage: Faster, more sensitive and less susceptible than culture methods (interference due to pretreatment). For the genetic identification of dermatophytes, characteristic DNA segments of genes such as mitochondrial genes, genes of chitin synthase, DNA topisomerase, superoxide dismutase, actin and tubulin are isolated, amplified by primers and detected by gel electrophoresis or ELISA.
  • Detection by MALDI-TOF analysis. For dermatomycoses still to be described as experimental. Already more widely used for mould infections.

The most important mycoses in humans

1. Brasch J (2012) News on diagnostics and therapy of mycoses. Dermatologist 63: 390-395
2. Nenoff, P et al (2014) Mycology - An Update Part 2: Dermatomycoses: Clinical picture and diagnostics. JDDG 12:749-778
3. Seebacher C et al (2007) Tinea of the free skin. J Dtsch Dermatol Ges 11: 921-926