MYCOLOGY & VIROLOGY

MYCOLOGY & VIROLOGY. BSMT 3 - B BALANOBA, AIZA BOROMEO, MICA ELIZABETH FERRER, ASHLY ESCUETA, REGINA JOY GONZALES, REGIL ANNE LAGA, TRISHA DIANNE.

[Audio] SYSTEMIC MYCOSES. SYSTEMIC MYCOSES.

[Audio] These are fungal infections of the body caused by fungal pathogens which can overcome the physiological and cellular defences of the normal human host by changing their morphological form. They are geographically restricted, and the primary site of infection is usually pulmonary, following the inhalation of conidia.· May be involve any of the internal organs of the body, including lymph nodes, bone, subcutaneous tissue, meninges, and skin..

[Audio] Etiologic agents: Blastomyces dermatitidis Coccidiodies immitis Histoplasma capsulatum Paracoccidioides brasiliensis.

[Audio] BLASTOMYCES DERMATITIS A thermally dimorphic fungus, causes blastomycosis. This fungus exists as a mold at room temperature in the laboratory and in the environment It is a yeast at 37°C in the laboratory and in human tissues..

[Audio] B.Dermatitidis Epidemiology Blastomycosis is acquired by inhalation of the conidia of the mold phase of B. dermatitidis from the environment. The organism is found in soil and rotting wood and vegetation, especially in those areas near to waterways. The endemic areas are the Mississippi and Ohio River basins, including the north central United States around the Great Lakes and extending into the Canadian Provinces of Manitoba and Ontario and the St. Lawrence Seaway..

[Audio] B. Dermatitidis - Morphology Can grow at room temperature ( Mold) lollipop ( oval) conidia, branching hyphae Can grow at 37˚C ( Yeast) Single broad based budding, thick walled, oval to round..

[Audio] B. Dermatitidis - Infections What host factors protect against this infection? Immunity to B. dermatitidis is comprised of both nonspecific innate responses and specific cell-mediated immunity. B. dermatitidis infects healthy individuals who are exposed to the aerosolized conidia. It is not more likely to infect immunosuppressed hosts. The tissue response to B. dermatitidis is a mixture of pyogenic and granulomatous inflammation. What are the clinical manifestations of infection with this organism? Pulmonary blastomycosis: Acute respiratory distress syndrome ( ARDS) occurs in a small proportion of patients who have pulmonary blastomycosis. Severe pulmonary involvement can be seen in patients with defective cell-mediated immunity, such as patients with AIDS. Disseminated blastomycosis: The skin, osteoarticular structures, and the genitourinary system (in men) are the most frequently involved sites of dissemination..

[Audio] How should I identify the organism? What tissue samples will provide the highest diagnostic yield? Lung biopsy and skin biopsy are most often helpful in diagnosing blastomycosis, but any organ that is involved can be sampled and sent for histopathological examination. The most appropriate stains for fungus identification in tissues are the periodic Schiff ( PAS) stain and the methenamine silver stain. What is the best treatment? Patients who have severe pulmonary or disseminated infection with B. dermatitidis should be treated initially with an amphotericin B ( AmB) formulation.

[Audio] PARACOCCIDIODES BRASILIENSIS The causative agent of a true systemic (endemic) mycosis called paracoccidioidomycosis. The spectrum of the disease is wide, varying from an asymptomatic infection verified by the skin test to a subclinical, symptomatic, or chronic infection. It is a thermally dimorphic fungus, growing as a mold in soil and as yeast in the host. It is also a South American endemic dimorphic fungus..

[Audio] P. Brasiliensis – Epidemiology Infection caused by P. brasiliensis is initiated by the inhalation of conidia into the lungs, after which the fungus may disseminate hematogenously or lymphatically to virtually all parts of the body. Primary pulmonary infections that subsequently disseminate most often manifest as mucosal lesions of the mouth, nose, and occasionally the gastrointestinal tract. Common in South America, most notably in Brazil Common in farmers Organism resides in the soil.

[Audio] P. Brasiliensis - Morphology The yeasts exhibit multiple circumferential narrow-based buds that on cross section have been compared with a ship's pilot wheel. Incubation period is undetermined. Tissue phase: translucent walled yeast cells with multiple buds Mariner's wheel or mickey mouse cap Mold phase: small one-celled conidia similar to B. dermatitis Septate hypha.

[Audio] P. Brasiliensis - Mode of Transmission People get paracoccidioidomycosis after breathing in the fungus Paracoccidioides from the environment in certain parts of Central and South America. Paracoccidioidomycosis does not spread from person to person. P. Brasiliensis - Disease / Infection Chronic granulomatous disease Skin Lymph nodes mucous membranes Lungs: Initial site of infection Ulcerative mucocutaneous lesions on face, mouth, and nose.

[Audio] P. Brasiliensis – Diagnosis Specimens: lower respiratory samples, specimens coming from lesions, lymph nodes, adrenal glands Direct Microscopy Molecular methods Culture 25- 30 C – colonies are flat, glabrous to leathery, wrinkled to folded, floccose to velvety, pink to beige to brown with a yellowish brown reverse 37 C – yeast cells Serology Exoantigen test: 1, 2, 3 ( antigens present) P. Brasiliensis – Treatment Antifungal drugs are the most effective therapeutics for paracoccidio-idomycosis. Among these are itraconazole, ketoconazole and fluconazole. Amphotericin B may be given to patients with severe disease who cannot tolerate other medications. Sulfonamides suppress the symptoms and halt the progress of the disease, but do not eliminate the fungus from the body..

[Audio] HISTOPLASMA CAPSULATUM A dimorphic fungus that remains in a mycelial form at ambient temperatures and grows as yeast at body temperature in mammals. ·These are oval-spherical in shape with a clear halo (that's the capsule) invading neutrophils. There is also a sneaky nucleated red cell..

[Audio] H. Capsulatum – Epidemiology Histoplasmosis is the most prevalent mycosis in North America and more often reported in the areas surrounding the Mississippi and Ohio rivers. Infection occurs via exposure to dust or soil for prolonged periods of time including activities which disturb bird and bat guano which increase the risk of infection. In Ohio and Mississippi River valleys, capsulatum is endemic and approximately 80 % of the general population tested showed hypersensitivity to Histoplasma capsulatum with young adults being the largest group to be affected. Although the course of infection is mild in immunocompetent individuals, the individuals with immunocompromised status are at an increased risk of infection, and hold an increased severity of infection with a higher mortality rate.

[Audio] H. Capsulatum – Morphology There are two varieties of capsulatum recognized: var. capsulatum and var. duboisii where H. capsulatum var duboisii is the cause of African histoplasmosis. The two varieties are indistinguishable in their mould forms, but there is a difference in their parasitic forms. The cells of the tissue form of duboisii are much larger and comprised of thicker walls than those of var. capsulatum. Growth on Sabouraud dextrose agar at 25ºC shows a white to brown colony, cottony mycelium after 2 to 3 weeks. The mold phase is characterized by thin, branching, septate hyphae that produce microconidia and a very distinct spore called a tuberculate macroconidium. Grown at 37ºC shows the budding yeast form. The yeast cell is 2- 4 µm in diameter and slightly oval in shape and found exclusively within macrophages.

[Audio] H. Capsulatum - Mode of Transmission Fungal spores can be released into the air when contaminated soil or droppings are disturbed. Breathing the spores may lead to an infection. The spores that cause this condition are commonly found in places where birds and bats have roosted, such as: caves, chicken coops, parks, older barns You can get histoplasmosis more than once. However, the first infection is generally the most severe. The fungus doesn't spread from one person to another and it's not contagious.

[Audio] COCCIDIODES IMMITIS A soil-dwelling dimorphic fungi, which is inhaled as arthroconidia ( spores). The organism lives in the soil in the mycelial phase, and, when inhaled, aerosolized infections particles are inhaled into the lungs of potential hosts. Once in the alveolar space, the organism multiplies, resulting in a giant spherule. Before the development of adaptive T-cell immunity, macrophages may ingest the organism but are unable to kill it. Dissemination of the organism can occur prior to the onset of adaptive immunity or in people with impaired cellular immune responses..

[Audio] C. Immitis – Epidemiology Coccidioides immitis exists in the semi-arid desert of the southwestern United States, northern Mexico, and Central and South America. C. Immitis - Mode of Transmission Coccidioidomycosis is spread by inhaling infective fungal spores found in the soil, usually as dust. It does not spread between people and/or animals. When and for how long is a person able to spread the disease? The disease cannot be spread from person to person.

[Audio] C. Immitis – Morphology It is a dimorphic fungus that exhibits morphological variation in its mycelial and parasitic forms. It exists in the desert soil as a mold. As the cells degenerate, barrel-shaped arthroconidia break off from the hyphae and become airborne. Arthroconidia undergo significant morphological changes following inhalation into the lung. Within living tissue, it typically swells and develops into a large spherule containing numerous endospores. Endospores are released from ruptured spherules and develop additional spherules in the infected host. Repeated cycles of endospore release and spherule formation in the lung lead to an area of pneumonitis; diagnosis is usually determined based on the presence of these endospores.

[Audio] C. Immitis – Diagnosis Most infection with C. immitis does not cause symptoms. The lungs are the most common organ infected. It is often abnormal chest X-rays or a CT scan of the chest (a type of X-ray that makes cross-sectional images of your body), that may raise the possibility of Valley fever A blood test for coccidioidal serology may also help to diagnose Valley fever. C. Immitis – Treatment In many cases of Valley fever, no treatment is necessary because symptoms disappear on their own. People with more serious infections may need antifungal medications to cure the infection. Doctors usually prescribe antifungal medications for a period of 3 to 6 months. In some severe cases, people require hospitalization or long-term antifungal treatment..

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