Clinical Mycology 7 Part 1 PDF

Systemic Mycoses (1) DR. WIFAG RABIH Systemic mycoses are fungal infections affecting internal organs. In the right circumstances, the fungi enter the body via the lungs, through the gut, paranasal sinuses, or skin. The fungi can then spread via the bloodstream to multiple organs including the skin,...

Systemic Mycoses (1) DR. WIFAG RABIH Systemic mycoses are fungal infections affecting internal organs. In the right circumstances, the fungi enter the body via the lungs, through the gut, paranasal sinuses, or skin. The fungi can then spread via the bloodstream to multiple organs including the skin, often causing multiple organs to fail and eventually resulting in the death of the patient. Sometimes are known as deep mycoses. They are difficult to eradicate and many patients with deep mycoses die in spite of extensive medical care especially when the central nervous system is involved. Humans acquire these mycoses only when the spores of the soil organisms are either inhaled or introduced into the body through a break in the skin. The systemic fungi include ◦ Blastomyces dermatitis (Blastomycosis), ◦ Coccidioides immitis (coccidioidomycosis), ◦ Histoplasma capsulatum (Histoplasmosis), ◦ Paracoccidioides brasiliensis (paracoccidioidomycosis). BLASTOMYCOSIS (Blastomyces dermatitidis) DIMORPHIC FUNGI Fungi that cause systemic infections have a limited geographic distribution where they occur most frequently. It grows at room temperature as a white or tan mold but grows within the host or at 37 0c as budding, round yeast-like cells. Geographic Distribution: The disease is endemic in South Eastern and South Central states of North America, along the Mississippi and Ohio Rivers. Source of infection: Outbreaks have been associated with occupational or recreational activities around streams or rivers with high content of moist soil enriched with organic debris and/ or rotting wood. Pathogenesis and clinical picture Blastomycosis is a chronic granulomatous disease which means that it progresses slowly.Although pulmonary and skin involvement is the most common, B. dermatitidis frequently affects bone, prostate, and other organs. More frequently blastomycosis presents as a cutaneous or respiratory disease. The cutaneous lesions may be primary (usually self-limiting) or secondary (a manifestation of systemic disease). Blastmycosis is acquired via inhalation of the conidia, which transforms into the yeast form once in the lungs. After 30 to 45 days an acute pulmonary disease indistinguishable from bacterial pneumonia may occur. However, at least 50% of primary infections are asymptomatic. A few patients have acute, self-limited pneumonia; fever productive cough, and are usually resolved within a month. The infection has three forms:  Acute pulmonary blastomycosis, even though it may resolve without treatment; however, treatment is often used.  Chronic pulmonary blastomycosis usually has granulomatous lesions in the upper lobe often misdiagnosed as carcinoma.  Disseminated blastomycosis is a progressive disease that follows hematogenous spread from unresolving pulmonary lesions by macrophages to remote sites, most commonly skin and bones. The patient who presents with a complaint of respiratory symptoms will frequently remark about the loss of appetite, loss of weight, fever, productive cough, and night sweats. While these symptoms resemble those of TB, it is not this disease. The X-ray shows obvious pulmonary disease. To make the specific diagnosis, the physician must be aware of blastomycosis. Laboratory Diagnosis Sputum sent to the lab for "culture" will not grow the organism. A pus specimen. by microscopic examination with KOH. Other specimens. include biopsy material and urine. Occasionally, the organism can be isolated from urine as it often infects the prostate If you request a fungus culture from the microbiology lab, they will incubate the cultures at 37º C and at 25º C because most of the significant pathogenic fungi are dimorphic. This organism has a characteristic appearance of a double contoured wall with a single bud on a wide base. Serology There are 3 serological tests used for blastomycosis: Immunodiffusion test (precipitin). This requires 2 to 3 weeks to become positive. Complement fixation (CF) test. This test requires 2 to 3 months after the onset of the disease to develop detectable antibodies. Enzyme Immunoassay (EIA). The latter test has met with mixed acceptance by mycologists. However, it is easy to perform and antibody is detected early in the disease process Treatment Itraconazole is a type of antifungal medication that is typically used to treat mild to moderate blastomycosis. Amphotericin B is usually recommended for severe blastomycosis in the lungs or infections that have spread to other parts of the body. Depending on the severity of the infection and the person’s immune status, the course of treatment can range from six months to one year. Coccidioidomycosis (Desert fever, valley fever, San Joaquin fever) Coccidioides immitis ◦ 60% asymptomatic. Only identified with positive skin test ◦ 40% mild to severe disease ◦ Can be fatal ◦ Immuno-compromised persons highly susceptible to serious infection The organism reproduces in host tissue by forming small endospores within mature spherules. After rupturing of the spherule, the released endospores enlarge and repeat the cycle. Coccidioides immitis Lifecycle phases Epidemiology  Geographic Distribution: Coccidioidomycosis is endemic in Central America, the Southwestern U.S.A., a small portion of South America, and Mexico.  Although the geographical distribution is well defined, cases of coccidioidomycosis may be seen in any part of the world because of the case of travel. Source of infection: ◦ The infective fungal spore is found in the soil. Natural disturbances or Human disturbances Pathogenesis and clinical picture A chronic, progressive, granulomatous disease occurs in less than 1% of those infected, especially immunosuppressed individuals; this granulomatous less resembles the tubercles of tuberculosis and cavitations may occur. The infection may disseminate to different parts of the body, including bones, viscera, and the CNS. The acute and most common forms of the disease resemble influenza. Approximately 60% of the cases remain asymptomatic and self-limiting. The initial symptoms of pulmonary infection consist of cough, fever, and malaise. One to two weeks later, about 3 to 5% of patients develop complications attributable to a hypersensitivity reaction, the most frequent being skin lesions (erythema) or joint symptoms. The symptoms of a chronic thin-walled cavity include cough or hemoptysis in half of the cases; fever and loss of weight the other half is asymptomatic. Laboratory Diagnosis Before collecting or sending any samples, the proper authorities should be contacted Samples should only be sent under secure conditions and to authorized laboratories to prevent the spread of the disease Direct Examination Sputum, lung biopsy, pus from lesions, and other clinical specimens Complement fixation ◦ IgG anticoccidial antibodies ◦ Titer 1:4 = current or recent infection ◦ Titer 1:32 = increased risk of extrapulmonary dissemination Skin test of epidemiological value Treatment &Vaccination Fluconazole Itaconazole. Amphotericin B (AmB). No effective immunization available ◦ Efforts are being made to develop a vaccine Precautionary measures should be taken to avoid infection ◦ Reduce exposure to soil and dust