Mycobioma

The term mycobiome, in analogy to the term microbiome (microbiota), refers to the totality of all commensal or pathogenic fungi that colonize humans or other living beings.

Fungi and bacteria are, since they are omnipresent in our environment, an integral part of our physical flora (microbiome) of skin, lungs, mouth, intestines and vagina. In the intestine, the composition of the fungi is influenced by age, immune system, nutrition, medication and existing bacteria. It is assumed that the mycobiome, as well as the bacterial colonization of organ surfaces, contributes to the physiological functions and homeostasis of the host.

Both commensal and pathogenic fungi can cause or aggravate skin diseases (Jo JH et al. 2016). Their composition depends on the condition of the host, but also on the nature of the affected body part (e.g. scalp, groin, interdigital space). Furthermore, age plays an important role in the composition of the mycobioma.

Interestingly, age also influences certain dermatophytoses (e.g. tinea capitis in children, onychomycoses in adults). In the skin mycobioma of healthy adults, lipophilic fungi such as Malassezia species dominate in most cases (Jo JH et al. 2016). Children (age <14 years) showed besides Malassezia globosa a more diverse fungal community, e.g. with Eurotiomycetes.

Currently it is still difficult to define when a mycobioma is healthy (Pranab K et al. 2015). Studies in healthy individuals have shown that e.g. in the gastrointestinal tract > 60 fungal genera and 184 species can be found, with Candida species being the dominant genus (Pranab K et al. 2015). Thus the mycobiome of the intestine is less diverse than its "bacterial" microbiome.

Commensals, "good" fungi and yeasts, can be a decisive factor in the prevention of pathological processes in the intestine. An example is the antagonistic interaction of Saccharomyces boulardii, a non-pathogenic yeast, and Clostridium difficile. In mice, the administration of S. boulardii led to an increased production of immunoglobulin A (IgA); furthermore, Saccharomyces boulardii protects against antibiotic-associated diarrhoea and recurrent colitis caused by Clostridium difficile (Qamar A et al. 2001).

1. Jo JH et al (2016) Various Human Skin Fungal Communities in Children Converge in Adulthood. J Invest Dermatol 136:2356-2363 Pranab K et al (2015) Mycobiota in gastrointestinal diseases. Nature Reviews Gastroenterology & Hepatology 12: 77-87
2. Qamar A et al (2001) Saccharomyces boulardii stimulates intestinal immunoglobulin A immune response to Clostridium difficile toxin A in mice. Infect. Immune 69:2762-2765.
3. Qiu X et al (2015) Changes in the composition of intestinal fungi and their role in mice with dextran sulfate sodium-induced colitis. Sci. Rep 5:10416.