The blastoconidia are protuberances or product infectious areas of a typical yeast asexual reproduction. These are also known as incipient yeasts and have been observed recurrently in pathogenic yeasts of the genus Candida.
All yeasts propagate constantly through this type of reproduction and the development of fungi of this type has been extensively studied, that is, the phenotypic change from blastoconidia until they become true hyphae. However, at present it is still unknown how the molecular mechanism that stimulates the development of blastoconidia into mature hyphae is activated.
Hyphae and blastoconidia of Candida albicans (Source: And also via Wikimedia Commons)
The best-documented blastoconidia are associated with the pathogenic species of yeast Candida albicans, a fungus that on many occasions can be a pathogen in animals (zoopathogens).
This species of fungus is frequently found in the oral cavity, in the intestine, on the skin and, when it is found in the female reproductive system, it is usually the cause of strong infections.
On rare occasions, it has been observed that candids that reproduce via blastoconidia can cause very serious systemic infections collectively called "paracoccidioidomycosis."
Blastoconidia are easy to identify under the microscope through periodic acid-Schiff staining, in which the walls are stained deep red and the central vacuole becomes light pink or almost colorless.
Yeasts of the genus
They are defined as dimorphic yeasts (which have two forms), they can be anascosporated and blastoporated, depending on the type of spores through which they reproduce. As they spread, they form a pseudomycelium and when grown in in vitro culture media they develop as "creamy" and "smooth" looking colonies.
Photograph of a Petri dish grown with Candida albicans (Source: CDC / Dr. William Kaplan via Wikimedia Commons)
These single-celled yeasts can be seen in different forms and many are endogenous to the human body. They are between 2 and 8 μm in diameter. These fungi can form structures called "chlamydospores".
Chlamydospores are terminal cells in the candida chain, they have a double cell wall and a diameter of 8 to 12 μm. They are structures of resistance against unfavorable conditions.
The excessive use of antibiotics alters the intestinal flora in mammals, which can trigger imbalances in the native microbial flora, which can cause infections by the fungi of the genus Candida that inhabit the tissue.
Candida reproduce exclusively through asexual reproduction, that is, these fungi do not produce "ascas", they only reproduce by budding or "germination" of blastoconidia formed from individuals that were the product of clonal reproduction.
Sometimes the blastoconidia that "sprout" do not separate from the stem cell, they only segment. This gives rise to a web-like network of "chains" that extends throughout the tissue, and this is what is known as a pseudomycelium.
Diseases reflected by the presence of blastoconidia
Generally, the abundant presence of blastoconidia in any tissue is a sign of an infection caused by an excessive proliferation of endogenous candida. The most common diseases are vulvovaginal candidiasis, infections in the respiratory and gastric tracts, and certain skin diseases.
Vulvovaginal candidiasis is very common in women (sexually active or not), it causes intense itching, pain and irritation, as well as burning when urinating. It is usually detected by a very thick and thin whitish vaginal discharge.
In the respiratory tract, this infection can have more severe complications. It generally causes breathing difficulties, as pseudomycelia can obstruct the bronchi, decreasing the individual's respiratory capacity.
Sometimes, organisms of the genus Candida can infect parts of the skin that are immunosuppressed or that are sensitive to the proliferation of these fungi by blastoconidia, which can cause infections such as dermatitis.
The pathogenic candida species are Candida parapsilopsis, Candida glabrata, and Candida albicans. The species Candida albicans is the cause of more than 55% of all vaginal infections, while the remaining 45% are caused by other types of candida and some bacteria.
Since all fungi are saprophytic organisms, they secrete enzymes to begin an exogenous digestion of the medium or substrate where they grow, which then allows them to assimilate it and thus feed themselves.
Each blastoconidia in contact with the medium also has the ability to secrete enzymes and digest the substrate where it is found.
Diagnosis
Diagnosing the presence of blastoconidia is possible by direct observations of body fluids under a microscope. Specialists take a sample or scrape from the epidermis of tissue that is thought to be infected and immerse it in a saline solution.
Said sample in saline solution is observed under the microscope in search of yeast cells. Usually the samples are stained to visualize the blastoconidia of the microorganisms.
Blastoconidia are easy to identify under the microscope through periodic acid-Schiff staining. The walls are stained an intense red color, while the central vacuole takes on a light pink or almost colorless color.
Staining can also be performed by other different methods, a very common one is staining by means of tetrazolium reduction, which is used to stain different species of candida.
However, the blastoconidia of Candida albicans do not stain with tetrazolium, so it is sometimes necessary to corroborate the presence of this species through more rigorous tests such as the polymerase chain reaction (PCR) technique or growth in vitro of microflora.
Treatments
Controlling the infection caused by candida and their blastoconidia requires constant and intensive treatment. However, it has been estimated that the percentage of people who are cured of these diseases is between 70 and 90% of all infected individuals.
The treatment that doctors usually prescribe consists of nystaine, either topical or oral. Nystatin is an antifungal characterized by having long carbon chains and a mycosamine group in its structure.
This acts by intercalating in the sterols of the cell membrane of the fungi, which destabilizes their structure and allows the free entry of ions and other molecules that interrupt the normal cell cycle of the fungus.
The treatments recommended for topical use are drugs with terconazole, nystatin, ticinazole, miconazole, clotrimazole or butoconazole; while orally fluconazole is used more.
Treatment should not be carried out for a long time, as it can alter the body's own microbiota once the infection is eradicated.
References
- Alasio, TM, Lento, PA, & Bottone, EJ (2003). Giant blastoconidia of Candida albicans: A case report and review of the literature. Archives of pathology & laboratory medicine, 127 (7), 868-871.
- Allen, CM (1994). Animal models of oral candidiasis: a review. Oral surgery, oral medicine, oral pathology, 78 (2), 216-221.
- Bottone, EJ, Horga, M., & Abrams, J. (1999). "Giant" blastoconidia of Candida albicans: morphologic presentation and concepts regarding their production. Diagnostic microbiology and infectious disease, 34 (1), 27-32.
- Dabrowa, NINA, & Howard, DH (1984). Heat shock and heat stroke proteins observed during germination of the blastoconidia of Candida albicans. Infection and immunity, 44 (2), 537-539.
- Kurzaątkowski, W., Staniszewska, M., & Tyski, S. (2011). Damage of Candida albicans blastoconidia exposed to biocides. Mycoses, 54 (5), e286-e293.
- van der Graaf, CA, Netea, MG, Verschueren, I., van der Meer, JW, & Kullberg, BJ (2005). Differential cytokine production and Toll-like receptor signaling pathways by Candida albicans blastoconidia and hyphae. Infection and immunity, 73 (11), 7458-7464