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 solution native preparation: Skin scales are dissolved in 20% potassium hydroxide solution. The microscopic image shows the fungal filaments without special coloration. Indication of fungal infection, but not species or even group affiliation (dermatophytes, yeasts, molds = DHS system). The sensitivity of direct microscopic detection is around 60%. The procedure should be carried out as a first diagnostic step.
  • Other stains: Certain stains (Congo red, methylene blue, chlorazole black) make fungi stand out particularly well against dander. Native preparations of pityriasis versicolor are particularly suitable for staining according to Parker (drip equal volumes of blue ink and KOH onto the preparation). The color is immediately absorbed by the Malassezia spp!
  • Periodic acid-Schiff staining (PAS ) in the histological preparation: In this highly sensitive histological method, fungal filaments and spores stain red. It is not possible to differentiate between molds, dermatophyte mycelium and pseudomycelium of pathogenic yeasts using this optical method.
  • Fluorescence microscopy: The microscopic diagnosis of potassium eyes is much more successful with the use of much more sensitive fluorescence microscopic methods with optical brighteners from the group of diaminostilbenes(Calcofluor white, Blankophor). These dyes bind specifically to the chitin of the fungal cell wall. Human keratin is only weakly stained (cave: cellulose e.g. cotton threads also fluoresce).
  • Wood light lamp: Greenish fluorescence, especially used for microsporia, favus, tinea inguinalis.
  • Culture (gold standard): On special culture media (e.g. Sabouraud glucose and Kimmig agar) dermatophytes grow within 1-4 weeks, molds within 1-2 weeks and yeasts within 3-4 days. A suspected diagnosis can be made based on the growth form and color of the culture.
  • Microculture: Precise microscopic differentiation by micro- and macroconidia, chlamydospores, shape and arrangement of blastospores and pseudomycelia.
  • Molecular diagnostics: PCR-supported genetic identification procedure. Advantage: Faster, more sensitive and less susceptible than culture methods (interference due to pre-treatment). For genetic identification of dermatophytes, characteristic DNA sections of genes such as mitochondrial genes, chitin synthase genes, DNA topisomerase, superoxide dismutase, actin and tubulin are isolated, amplified using primers and detected using gel electrophoresis or ELISA methods. DNA chip technology is used for dubious clinical and mycological primary diagnostics (Bieber K et al. 2021). The costs of DNA chip technology are around 5-6 times higher than detection by dirketone and culture.
  • Detection by means of MALDI-TOF analysis. Still considered experimental for dermatomycoses. Already widely used for mold infections.

The most important mycoses in humans

1. Bieber K et al (2021) DNA-chip based diagnosis of onychomycosis and Tineda pedis. JDDG 20:1112-1122
2. Brasch J (2012) News on the diagnosis and therapy of mycoses. Dermatologist 63: 390-395
3. Nenoff, P et al. (2014) Mycology - an update part 2: Dermatomycoses: Clinical picture and diagnosis. JDDG 12:749-778
4. Seebacher C et al (2007) Tinea of the free skin. J Dtsch Dermatol Ges 11: 921-926