In microbiology, Geotrichum candidum is the name given to milk fungi that colonize the acidic environment of many dairy products. In the human intestine, oral mucosa, and lungs, the fungi occur naturally and are not associated with discomfort or benefit for healthy individuals. Immunodeficient patients may develop geotrichosis due to the fungi.
What is Geotrichum candidum?
Microorganisms of the genus Geotrichum candidum are yeast-like fungi that feed on putrefactive matter. Their mode of nutrition makes the fungi saprophytic organisms that are found primarily in acidic environments. Hyphae characterize the fungus. These are thread-like cells. In hyphal fungi, the entire fungus is composed of hyphae. The individual hyphae are divided into different sections by partitions. The dividing walls run transversely through the Geotrichum candidum and are also called septa. In the fungal genus Geotrichum candidum, the hyphae break down into rectangular arthrospores. The individual segments of the fungi thus become spores. The fungi do not form shoot cells. Arthrospores are conidia and thus typical propagation organs for the reproduction of higher fungi. Due to their preferred living environment, fungi of the genus Geotrichum candidum are also known as milk fungi. They belong to the group of molds and thus to a systematically heterogeneous group of filamentous fungi. Meanwhile, medical science assumes a possible differentiation into pathogenic and apathogenic strains.
Occurrence, distribution, and characteristics
Fungi of the genus Geotrichum candidum live predominantly in acidic environments of food and are thus saprophytic in the human environment. Possible habitats of the fungal genus are vegetable plants such as tomatoes, fruits, milk and dairy products, such as Harz cheese, Camenbert and other cheeses. The fungi are essential in the formation of flavors in the production of fine cheese. The fungi are also found in the soil and in sewage. Various strains of the genus also live in the human body, where they are known as humen parasites and have discovered niches for themselves. In addition to apathogenic saprophytic colonization of the intestine, subgenera of the fungal species can also pathogenically colonize the intestine and lungs. In addition, mold species of the genus Geotrichum candidum are in some cases known as notifiable plant diseases. In this context, among other things, they produce fungal toxins in spoiled food. However, their use as food refiners is equally widespread. In addition, the fungi are used as a biological source for antibiotic production and the production of cholesterol-lowering drugs. Under the name “Geotrichum candidum”, the fungal genus is almost unknown. Most people know the mold as milk mold on soured milk or curd cheese. The fungi manifest themselves on milk and milk products in the form of fine down with whitish yellow color. Their culture behavior is characterized by yeast-like growth, which initially takes place without aerial mycelium. For this reason, the cultures are easily confused with yeast fungi. At room temperature, filaments appear in the agar and aerial hyphae are formed. The decay of the aerial hyphae into arthrospores is also enormously similar to the sprouts of yeasts. The arthroconidia are hyaline and smooth. They form unicellularly and occur in rectangular or cylindrical shapes with varying sizes. True blastoconidia (cells by sprouting) are not formed by fungi of the genus Geotrichum candidum. The fungal genus is characterized as a fast-growing genus that forms moist lackluster and flat colonies. The surface of the colonies may appear whitish, light gray, or yellowish. A felt-like surface texture is evident on the colonies. A cottony eruption lies centrally and a halo of rays forms peripherally. Younger cultures typically have a fruit-like odor. Older cultures, on the other hand, have a cheesy odor. The genus Geotrichum candidum is distributed worldwide and is rarely pathogenic. In the digestive tract and oral cavity, its presence usually has neither disease value nor benefit to humans.
Diseases and ailments
As a rule, the genus Geotrichum candidum does not cause problems to healthy people and leads a rather inconspicuous existence in contact with them. However, in people with diseases of the gastrointestinal tract or people with a reduced immune system, the genus can cause geotrichosis.This is an infection classified as opportunistic with pulmonary involvement. Clinically, the infection shows a variable manifestation. In broncho-pulmonary involvement, caverns with diffuse peribronchitic or tumorous infiltrates or abscesses form. In addition, skin symptoms may manifest. These include, in particular, interdigital mycosis (athlete’s foot). Inflammatory granulomas of the extremities, face or capillitium may also occur. Rather rare is an infestation of the oral mucosa, which produces the picture of stomatitis. The most relevant complication of the infestation in immunodeficient patients is sepsis, i.e. systemic blood poisoning. Diagnosis of geotrichosis is made by microscopic cultural fungal detection from bronchial secretions and mucous membranes. In case of skin infestation, smears of the skin show the colonization. Final confirmation of the diagnosis is made by histological pathogen detection. Patients usually receive imidazole antifungals, such as ketoconazole, for treatment. Application in ointment form is local. If organs are affected, internal therapy must take place, which in most cases corresponds to systemic treatment and is similar to the therapy of Candida sepsis. The course is to be classified as rather unfavorable from the time sepsis has occurred.
