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Medical Mycology (Systemic Fungal Pathogens: all cause pneumonia, can…
Medical Mycology
Systemic Fungal Pathogens: all cause pneumonia, can disseminate, but not common. Not transmitted person-to-person. Granuloma on tissue.
Histoplasma capsulatum
Dimorphic: mold (and conidia) at 25 C, yeast at 37 C. Growth may take weeks. NOT encapsulated
Endemic area: US Midwest, Ohio and Mississippi Rivers Valleys. Associate with bird and bat droppings
Most cases are asymptomatic, can result in progressive pulmonary disease with weight loss
Diseases: Disseminated disease (skin, CNS, GI, adrenal glands) can occur. Reticuloendothelial system, splenomegaly and mouth ulcers
Diagnosis: antigen detection, culture and path (small, narrow budding yeast)
Treatment: Amphotericin, itraconazole
Blastomyces dermatitidis
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Diagnosis: Culture, large yeasts with broad-based buds on KOH prep or tissue
Diseases: Disseminated disease possible, skin nodules and ulcers, as well as bone lesions. RARELY ASYMPTOMATIC
Tx: Amphotericin, Itraconazole
Coccidioides immitis
Diseases: Can be asymptomatic (most cases) to disseminated (rare in immunocompetent hosts). Eosinophilic meningitis, erythema nodosum (inflammation of hypodermis), arthralgia
Endemic area: US Southwest (including Utah) - Valley Fever (San Joaquin Valley) and/or Desert Rheumatism
Diagnosis: culture, anntibody etection (serum, CSF), spherules in tissue
Tx: Fluconazole, Amphotericin
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Cryptococcus: Encapsulated yeast that is visible via India ink prep. Ubiquitous in soil, pigeon droppings, eucalyptus treas. C. neoformans is most common.
Diagnosis: Cryptococcus antigen (serum, CSF), culture
Disease: pneumonia and meningitis in immunocompromised, especially AIDS and SOT
Ubiquitous in soil, pigeon droppings, eucalyptus trees
Treatment: Amphtericin plus flucytosine, followed by fluconazole
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Opportunistic Fungal Pathogens: Primary immunodeficiencies, AIDS, immunosuppression, DM
Candida spp: Yeast, pseudohyphae and true hyphae can be seen during tissue invasion
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Disease: Mucocutaneous oral/esophageal thrush with white plaques, diaper rash, vaginal with thick white discharge and intense pruritus. Can disseminate.
Diagnosis: KOH prep, gram stain, culture
Treatment: Topical azoles, nystain. For invasive, use amphotericin B, fluconazole, echinocandins
Aspergillus spp: Mold that grows rapidly with branching, acute angle, septate hyphae
Widely distributed in the environment, spreads via heat-resistant conidia, can infect via inhalation and spread through air ducts
Treatment: voriconazole is preferred, isavuconazole, amphotericin and echinocandins are alternatives. Surgical debridement
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Diagnosis: culture, bipsy (septate hyphae with 45 degree angle)
Pneumocystitis
Diseases: interstitial pneumonia in immunocompromised, especially AIDS and high dose steroids may require prophylaxis
Not possible to culture. Bronchoalveolar lavage, methenamine silver stain, direct immunofluorescence
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Treatment: TMP/SMX preferred, atovaquone, pentamidine (for sulfa allergies), dapsone
Zygomycetes (Mucorales): Mold. Broad, nonseptated, wide angle branching hyphae.
Diseases: pulmonary or rhinocerebral disease, angioinvasive. Rapidly fatal
Treatment: control of diabetes, amphotericin or some azoles (posaconazole and isavuconazole), surgical debridement
Patients with diabetes mellitus (thrive in high glucose, acidic environment) or immunosuppression/neutropenia
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