Candida fungi (candida) are pathogens of candidiasis
Last reviewed: 23.04.2024
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Fungi of the genus Candida (candida) cause superficial, invasive and other forms of candidiasis (candidymycosis). There are about 200 species of fungi of the genus Candida. Taxonomic relationships within the genus are not well understood. Some of the genus are deuteromycetes; sexual reproduction of which is not established. Teleomorphic genera, including representatives with the sexual mode of reproduction: Clavispora, Debaryomyces, Kluyveromyces and Fichia, have also been identified.
Clinically significant species are Candida albicans, C. Tropicalis, S. Catenulara, S. Cijferrii, S. Guilliermondii, C. Haemulonii, C. Kefyr (formerly C. Pseudotropicaiis), C. Krusei, C. Lipolytica, C. Lusitaniae, C norvegensis, C. Parapsilosis, S. Pulherrima, S. Rugnsa, C. Utilis, S. Viswanathii, C. Zeylanoides and C. Glahrata. The leading role in the development of candidiasis has C. Albicans, followed by C. Glabrata, C. Tropicali and C. Parapsilosis.
[Morphology and Physiology of Candida
Fungi of the genus Candida consist of oval budding yeast cells (4-8 μm) pseudohyf and septate hyphae. Candida albicans is characterized by the formation of a growth tube from the blastospore (kidney) when placed in serum. In addition, Candida albicans forms chlamydospores - thick-walled two-contour large oval spores. On simple nutrient media at 25-27 ° C they form yeast and pseudohyfal cells. Colonies are convex, shiny, creamy, opaque with various varieties. In tissues candida grow in the form of yeast and pseudohyf.
Pathogenesis and symptoms of candidiasis
The development of candidiasis is promoted by improper administration of antibiotics, metabolic and hormonal disorders, immunodeficiencies, increased skin moisture, damage to the skin and mucous membranes. Most candidiasis is caused by Candida albicans, which produces proteases and inghegrine-like molecules for adhesion to extracellular proteins and other virulence factors. Candida can cause visceral candidiasis of various organs, systemic (disseminated or kandilasepticemia) candidiasis, superficial candidiasis of mucous membranes, skin and nails, chronic (granulomatous) candidiasis, allergy to Candida antigens. Visceral candidiasis is accompanied by inflammatory lesions of certain organs and tissues (esophageal candidiasis, candida gastritis, candidiasis of the respiratory system, candidiasis of the urinary system). An important sign of disseminated candidiasis is fungal enfoltalmitis (exudative change of the yellow-white color of the choroid of the eye).
When the candidiasis of the mouth on the mucous membranes develops an acute form of the disease (the so-called thrush) with the appearance of white cheesy plaque, possibly the development of atrophy or hypertrophy, hyperkeratosis of the papillae of the tongue. When candidiasis of the vagina (vulvovaginitis) appears white curdled discharge, edema and erythema of the mucous membranes. Skin lesions develop more often in newborns; on the trunk and buttocks are observed small nodules, papules and pustules. Candida allergy of the gastrointestinal tract, allergic damage to the organs of vision with the development of itching of the eyelids, blepharoconjunctivitis are possible.
Immunity
Cellular immunity predominates. Phagocytes-mononuclears, neutrophils, fascinating elements of fungi participate in protecting the body from candidiasis. Develops HRT, granulomas are formed with epithedioid and giant cells.
Epidemiology of candidiasis
Candida are part of the normal microflora of mammals and humans. They live on plants, fruits, as part of normal microflora, they can invade tissue (endogenous infection) and cause candidiasis in people with weakened immune defense. Less often the pathogen is transmitted to children at birth, with breastfeeding. When sexually transmitted, the development of urogenital candidiasis is possible.
Microbiological diagnosis of candidiasis
In the smears of the clinical material, pseudomycelia is identified (the cells are connected by constrictions), mycelium with septa and budding blastospores. Crops from the patient are carried out on Saburo agar, wort agar, etc. Colonies S. Albicans are whitish-creamy, convex, round. Fungi differentiate according to morphological, biochemical and physiological properties. Kinds of candidias differ when growing on glucose carotene agar by the type of filamentation: the location of the glomerulus - accumulations of small rounded yeast-like cells around the pseudomycelia. For blastospore, Candida albicans is characterized by the formation of growth tubes when cultured on liquid media with serum or plasma (2-3 hours at 37 ° C). In addition, Chlamydospores are detected in Candida albicans: the rice agar planting site is covered with a sterile cover slip and, after incubation (at 25 ° C for 2-5 days), is microscopized. Saccharomycetes, in contrast to Candida spp., Are real yeast and form ascospores located inside cells stained with a modified method according to Tsiol-Nielsen; Saccharomyces do not usually form pseudomycelia. The presence of candidemia is established with a positive blood culture with the release of Candida spp. From the blood. Candidiasis uroinfection is established when more than 105 colonies of Candida spp. Are detected. In 1 ml of urine. It is also possible to carry out serological diagnostics (agglutination test , RSK, RP, ELISA), antibodies to Candida albicans in the blood, and setting a skin-allergic test with candida-allergen. Candida albicans antigen detection is also used
Treatment of candidiasis
Treatment of candidiasis is based on the use of such drugs as: nystatin, levorin (for the treatment of local surface fungal infections, eg oropharyngeal), clotrimazole, ketoconazole, caspofungin, itraconazole, fluconazole (does not act on S. Krusei many C. Glabrata strains).