OPPORTUNISTIC MYCOSES

INTRODUCTION: Opportunistic mycoses (OM) that affect skin and mucosa as well as internal organs are caused by both yeast and molds. A precondition for development of such infections is a pronounced weakness in the host’s immune defenses. Candidiasis is an endogenous infection. Other OMs are exogenous infections caused by fungi that naturally inhabit the soil or plants. These environmental fungi usually invade via the respiratory tract. The most important are aspergillosis, cryptococcosis, and the mucormycoses. Besides Candida and other yeasts, phaeohyphomycetes and hyalohyphomycetes, which are only very mildly pathogenic, can also cause systemic infections. All OMs have a primary infection focus, usually in the upper or lower respiratory tract. From this focus, the pathogens can disseminate hematogenously and/or lymphogenously to infect additional organs. Infection foci should be removed surgically if feasible. Antimycotic agents are used in chemotherapy. It should be noted that, at least 70% of all human Candida infections are caused by C. albicans, the rest by C. parapsilosis, C. tropicalis, C. guillermondii, C. kruzei, and a few other rare Candida species.

MORPHOLOGY AND CULTURE: Gram staining of primary preparations reveals C. albicans to be a Gram-positive, budding, oval yeast with a diameter of approximately 5 μm. Gram-positive pseudohyphae are observed frequently and septate mycelia occasionally. C. albicans can be grown on the usual culture mediums. After 48 hours of incubation on agar mediums, round, whitish, somewhat rough-surfaced colonies form. They are differentiated from other yeasts based on morphological and biochemical characteristics.

PATHOGENESIS AND CLINICAL PICTURES: Candida is a normal inhabitant of human and animal mucosa (commensal). Candida infections must therefore be considered endogenous. Candodoses usually develop in persons whose immunity is compromised, most frequently in the presence of disturbed cellular immunity. The mucosa are affected most often, less frequently the outer skin and inner organs (deep candidiasis). In oral cavity infections, a white, stubbornly adherent coating is seen on the cheek mucosa and tongue. Pathomorphologically similar to oral soor is vulvovaginitis. Diabetes, pregnancy, progesterone therapy, and intensive antibiotic treatment that eliminate the normal bacterial flora are among the predisposing factors. Skin is mainly infected on the moist, warm parts of the body. Candida can spread to cause secondary infections of the lungs, kidneys, and other organs. Candidial endocarditis and endophthalmitis are observed in drug addicts. Chronic mucocutaneous candidiasis is observed as a sequel to damage of the cellular immune system.

DIAGNOSIS: This involves microscopic examination of preparations of different materials, both native and Gram-stained. Candida grows on many standard nutrient mediums, particularly well on Sabouraud agar. Typical yeast colonies are identified under the microscope and based on specific metabolic evidence. Detection of Candida-specific antigens in serum is possible using an agglutination reaction with latex particles to which monoclonal antibodies are bound. Various methods are used to identify antibodies in deep candidiasis (agglutination, gel precipitation, enzymatic immunoassays, immunoelectrophoresis).

THERAPY: Nystatin and azoles can be used in topical therapy. In cases of deep candidiasis, amphotericin B is still the agent of choice, often administered together with 5-fluorocytosine. Echinocandins (e.g., caspofungin) can be used in severe oropharyngeal and esophageal candidiasis.

EPIDEMIOLOGY AND PREVENTION: Candida infections are, with the exception of candidiasis in newborn children, endogenous infections.

RELATED;

1. HIV/AIDS  

2. IMMUNITY  

3. NORMAL FLORA OF THE HUMAN BODY

4.  MEDICAL MICROBIOLOGY

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