Medical mycology is the applied science of disease-causing fungi. Human pathogenic fungi of various genera and species represent potential pathogens for the organism.
What is medical mycology?
Medical mycology is the applied science of disease-causing fungi. Human pathogenic fungi of various genera and species represent potential pathogens for the organism. Mycology, as the study of fungi, is a branch of medical microbiology, which also includes bacteriology, virology and parasitology. Medical mycology in particular deals exclusively with the so-called human pathogenic fungi. Fungi, unlike many pathogenic bacteria, are never obligate pathogens. Their pathogenic potential tends to be considered rather minor. Nevertheless, facultative pathogenic fungi play an important role in clinical practice, because fungal infections occur frequently even in western industrialized countries. Whether a person develops symptoms of disease due to a fungus always depends on his or her individual immune status. Pathogenic fungi are opportunists, i.e. they only lead to an infectious disease, known as mycosis, if a person’s cellular immune defenses are so weakened by an underlying disease, such as cancer or AIDS, that fungi can spread and multiply. In hospitals, fungal infections are feared in immunocompromised patients because they are difficult to treat. Therefore, fungal infections have about the same status in the clinical setting as infection with multidrug-resistant germs, MRSA.
Treatments and therapies
Not all naturally occurring fungi and their permanent forms, spores, are dangerous to humans. Because they are microfungi that can cause infections in very different parts of the body, symptoms often resemble those of bacterial infections. However, antibiotics do not help against pathogenic fungi, but only specially developed antifungal agents, the so-called antifungal agents. This class of active ingredients can be used topically or systemically; in the case of topical, i.e. local, application, the antifungal active ingredients are applied to the affected skin areas, for example, in the form of skin creams or ointments. This form of application carries far fewer risks and side effects than systemic, intravenous application by infusion. Generalized fungal infections in immunosuppressed patients are still very difficult to control therapeutically, and the mortality rate is correspondingly high. Disease patterns caused by fungi are also referred to by the generic term mycopathy. This also includes food poisoning caused by the accidental consumption of poisonous mushrooms such as tuberous-leaved mushrooms. If left untreated, the consumption of poisonous mushrooms can lead to death. In addition to classic mushroom poisoning, also known as mycetism, poisoning can also occur from food contaminated with mushroom toxins. These so-called mycotoxicoses occur when foodstuffs are contaminated with certain fungal toxins such as aflatoxins. These foods then usually have a musty, foul odor. Many humans react additionally also allergic to individual mushroom components, the disease pictures developing thereby are called Mykoallergosen. The medical Mykologie in the narrower sense is concerned however exclusively with the Mykosen, thus the illnesses caused by pathogenic microfungi in the living tissue. Normally, an intact immune system prevents microfungi from growing, but if the immune system is weakened, invasive growth and thus fungal spread in the tissue with corresponding symptoms of disease can occur. Mycoses are classified in medical nomenclature according to their localization. The most important human mycoses are mucosal mycoses, cutaneous mycoses, and organ mycoses and systemic mycoses as the most severe clinical picture.
Diagnosis and examination methods
Pathogen detection of human pathogenic fungi requires a similar procedure in medical microbiology as the detection of bacteria or viruses. Human pathogenic fungi are classified into the so-called DHS system for differentiation and classification. This well-established diagnostic system includes the 3 most important fungal genera that can cause infections in humans.These are dermatophytes, yeasts and molds. All 3 fungal genera can cause similar inflammatory symptoms, so that differential diagnosis is only possible in the mycological laboratory. Native microscopy is one of the most important advanced diagnostics of mycoses. For this purpose, specimen material is taken from suspicious skin areas and examined directly under the light microscope without further preparation. A fungal infestation of the skin can be seen under the light microscope by the typical sprouting cells, which show a high cell division rate. Dermatophytes or molds can also be reliably detected on the basis of their known morphology. However, further serological examination methods must follow in order to determine the genus and species of a fungus beyond doubt. For this purpose, the sample material must be applied to a culture medium and incubated for at least 24 hours at 37 degrees Celsius in an incubator. Selective fungal culture media such as the glucose agar according to Sabouraud contain nutrient substrates adapted to human pathogenic fungi, with which the fungi from the sample material can optimally multiply for further identification. The most common fungal infection in humans is nail fungus, onychomycosis, usually caused by Trichophyton, a member of the dermatophyte genus. The most common fungus detected in human infections is Candida albicans, a member of the yeast group. Human pathogenic fungi are ubiquitously distributed both natively and in their permanent forms, spores. Transmission from person to person is therefore always possible and cannot always be reliably avoided even by the best hygiene and disinfection measures. However, transmission usually occurs through adherent spores on inanimate objects such as changing rooms or showers. The most important classes of active agents against human pathogenic fungi, antimycotics, include local azoles such as ciclopiroxolamine or ketoconazole. In severe cases with systemic infestation or organ fungus, terbinafine, griseofulvin, or amphotericin B as broad-spectrum antifungals orally or by infusion.
