Yeast – Infection, Transmission & Diseases


Yeasts are eukaryotic protozoa. About 60 different genera of yeast fungi with 500 species are currently known.

What are yeast fungi?

Yeast fungi are unicellular fungi . Since they have a cell nucleus , they belong to the eukaryotes. Since the yeasts multiply by fission or budding, they are also called sprout fungi. Most yeast fungi belong to the sac fungi ( Ascomycota ). But also different stages of development of other fungi are called yeasts.

In contrast to bacteria , yeast fungi have the complex cell structures of eukaryotes. They have complex membrane structures, possess chromosomes , and feature cell organelles such as mitochondria and endoplasmic reticulum .

Most yeasts are facultatively anaerobic. They prefer life when oxygen is available , but can also exist without oxygen. In the case of oxygen, the yeast fungi use the oxidative energy metabolism. They can produce carbon dioxide and water from different types of sugar. In the absence of oxygen, the yeast fungi also use sugar, but they only produce alcohol and carbon dioxide.

Occurrence, Distribution & Properties

Yeast fungi are widespread in the environment, so humans are actually constantly confronted with them. With a normal diet, it is difficult to prevent yeast fungi from entering the intestine . Vegetable components of food in particular are naturally contaminated with yeast fungi.

The yeast Geotrichum candidum is often found on the peel of pome fruit . Grapes and berries also have a wide variety of fungi on their surface. Fresh raw vegetable salads are often particularly contaminated. According to the recommendations of the German Society for Hygiene and Microbiology (DGHM), ready-to-eat salads, such as those offered at salad bars, may contain up to 5,000,000 colony-forming units per gram. A raw vegetable salad weighing 200 grams can therefore contain several billion yeast fungi.

The yeasts have a high resistance to gastric acid , so it can be expected that a large part of the fungi will also reach the intestinal tract. Normally, digestion by digestive enzymes takes place in the intestine. Some specimens of yeast fungi survive even this. Usually, however, the yeast fungi do not succeed in settling permanently in the intestine if the colonization resistance is intact.

Researchers and scientists are still arguing to this day as to whether or not yeast and mold are part of the normal intestinal flora. So far, they have tended to be assigned to the transient flora. This means that while they pass through the intestinal tract, they do not remain permanent residents. However, yeast is always present in the stool of a certain percentage of the population . As a rule, however, the germ count does not exceed 10² colonization-forming units per gram of stool. Useful functions of yeast fungi are not yet known.

Diseases & Ailments

Conversely, fungi in the body do not necessarily lead to a disease. Yeast fungi are therefore not among the obligatory pathogens. They only acquire pathogenetic relevance when the body is weakened. This weakness can be caused by childbirth , old age, immunosuppression , diabetes mellitus , operations or stress .

If the infection is limited to certain areas or organs , it is referred to as a local infection or organ mycosis. Spreading via the bloodstream, on the other hand, is called system mycosis. Most fungal infections are found in the gut. The yeast fungi Candida albicans , Candida tropicalis , Candida glabrata , Candida krusei and Geotrichum spp. most frequently detected. The species Candida stellatoidea , Candida parapsilosis , Candida guilliermondii and Candida lusitaniae are found less frequently. The dominant species is the Candida albicans.

If the intestinal mucosa and the colonizing colonization resistance allow it, the yeast fungi adhere to the intestinal mucosa. Yeast fungi are extremely adaptable. Depending on the pH value , oxygen content and nutrient supply, they change their appearance. Due to this antigen variability, they often escape the body’s immune system. The transformation into a filamentous form is particularly feared. The so-called pseudohyphae not only adhere particularly well, they can also grow into the mucous membrane.

As the yeast fungi multiply in the intestines, there is an increased incidence of dead cells . These cells degenerate, releasing antigens as they do so . The antigens enter the bloodstream via the damaged intestinal mucosa. If an allergic disposition is present, they can cause allergies here .

In addition, under certain conditions, the yeast fungi produce ethanol and fusel oils as well as isoamyl alcohol or isobutanol when processing carbohydrates . Especially in the case of long-term fungal infestation, the liver is heavily burdened by the accumulated fusel alcohols.

Recent studies indicate that the yeast Candida albicans not only produces alcohols but also toxins. Animal experiments have shown that these toxins damage lymphocytes , enterocytes and glial cells .

However , candidiasis can not only occur in the intestine. Various species of Candida also live in the throat or esophagus . In the mouth , the oral mucosa under dentures is particularly affected. In a so-called thrush (candidiasis), the tongue is covered with a white layer of fungus.

Infection of the vagina with yeast fungi is also known as vaginal mycosis . Colloquially, the disease is simply called vaginal fungus. As a rule, Candida albicans is also the cause here. A vaginal mycosis is expressed by a white discharge with itching . White deposits that cannot be wiped off become visible on the vaginal mucosa. The skin changes can extend to the inside of the thighs and cause severe itching there. Fungal infections of the vagina often occur in combination with bacterial vaginal infections.








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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.