Candidiasis- Opportunistic Mycoses
Opportunistic mycoses refer to the infections caused by fungi in hosts with immune-compromised conditions. The fungi involved in the infection are called as opportunistic fungi. The reasons behind this incidence include the overuse of antibiotics, corticosteroids, and immunosuppressive drugs.
Candidiasis is an infection of the skin, mucosa, and internal organs. The main causative organism behind the infection is Candida albicans (80-90% cases). Candida albicans is normally found in skin, gastrointestinal tract, oral and vaginal cavities.
C. albicans is a spherical yeast cell. A unique characteristic of C. albicans is the presence of pseudohyphae in both cultures and tissues. The pseudohypha is elongated filamentous cells joined end to end and has similarity with the fungal hypha.
Species of Candida
The important species of Candida found in the human body are (Apart from C. albicans)
- C. stellatoidea
- C. tropicalis
- C. krusei
- C. galbrata
- C. parapsilosis
Candidiasis refers to an opportunistic endogenous infection. There are several factors directly connected with the infection such as diabetes, immunodeficiency, malignancy, overuse of antibiotics, immunosuppressive drugs, and intravenous catheters. Different types of lesions are caused by Candida such as
- Oral thrush
Skin and nail infections
- Skin: Infections of axillae, groin, perineum and submammary folds where the skin is macerated by perspiration, napkin dermatitis in infants.
- Nail: Infections of finger webs, nail folds, and nails. Paronychia and onychia cab also be observed.
Chronic mucocutaneous candidiasis
It is a physical condition occurred due to the immune disorder of T cells. Chronic infection with Candida is the primary characteristic of the condition. The infection occurs in mucosal surface, skin, and nails and remains only in those areas. The condition is associated with viral infection caused by HIV, human papilloma virus, etc.
- Urinary tract infection.
- Intestinal candidiasis.
- Pulmonary candidiasis.
- Samples collected from skin lesions, nails or mucous membranes can be stained by gram staining. Gram-positive budding yeast will confirm the presence of Candida.
- Candida is present in human skin, therefore, high numbers of cells will confirm the infection.
- The presence of pseudohyphae will indicate tissue invasion by candida.
- The samples collected from the infected parts need to be inoculated in Sabourds Dextrose agar or Yeast Malt agar and need to be incubated at 25-300C for 24 to 48 hours.
- Cream colored, smooth, pasty colonies will indicate the presence of Candida.
- Observation of gram-positive budding yeast will confirm the result.
C. albicans have some specific characteristics which are important to differentiate it from other Candida species. The following tests need to be performed to understand the difference
- Germ Tube Test: The candida isolated from the sample need to be inoculated in human serum at 370C for two hours. The presence of a germ tube will confirm the presence of Candida albicans.
- Chlamydospore: Isolated Candida samples need to be isolated in cornmeal agar. The presence of Chlamydia under the microscope will confirm the sample as Candida albicans.
- Carbohydrate fermentation and carbohydrate assimilation test.
Precipitation test with a carbohydrate extract of candida is used for serological studies. Tests for precipitins in serum are available for C. albicans e.g. CIEP.
ELISA is used to find out specific antigens of Candida albicans.
Cell-mediated immunity helps to identify the infection and the intensity of the infection can also be understood.
- Removal of predisposing factors.
- The topical application of nystatin or imidazole can help to reduce superficial infections.
- Amphotericin B along with 5-fluorocytosine can be used in systemic infection.
- Glocker, E. and Grimbacher, B., 2010. Chronic mucocutaneous candidiasis and congenital susceptibility to Candida. Current opinion in allergy and clinical immunology, 10(6), pp.542-550.
- Odds, F.C., 1994. Pathogenesis of Candida infections. Journal of the American Academy of Dermatology, 31(3), pp.S2-S5.
- Richardson, M.D., 1991. Opportunistic and pathogenic fungi. Journal of Antimicrobial Chemotherapy, 28(suppl_A), pp.1-11.
- Textbook of Microbiology, Prof. C.P. Baveja, Arya Publication.
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