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04 Deja Review-Micro Opportunistic Mycoses

Terms in this set (24)

What are the most common opportunistic mycoses?
Candidiasis caused by Candida
Invasive aspergillosis caused by Aspergillus Cryptococcal meningitis caused by Cryptococcus
Zygomycosis caused by Mucor, Rhizopus, and related species
Interstitial pneumonia caused by Pneumocystis jiroveci
Describe the morphology of Candida albicans:
Candida albicans is an oval yeast with a single bud that forms pseudohyphae and true hyphae when it invades tissue. It exists simultaneously as mold and yeast form.
Where is C. albicans usually found?
Candida albicans is the most common cause of fungal infections in immunocompromised
patients. It is indigenous to the oropharyngeal membrane.
What diseases does C. albicans cause?
Mucocutaneous candidiasis (oralthrush, esophagitis, gastritis, and vaginitis). Up to 90% of human immunodeficiency virus (HIV) patients on highly active antiretroviral therapy (HAART) will eventually develop mucocutaneous candidiasis. 75% of all women will have at least one episode of vaginal candidiasis. Systemic candidiasis with mortality rates of 30% to 40%. Candida is also the leading cause of fungal endocarditis.
Mnemonic: Treat w/CVS (a pharmacy) Meds (Carditis, Vaginal, Systemic, Muco- cutaneous)
How is C. albicans diagnosed?
Potassium hydroxide (KOH) smear shows pseudohyphae, true hyphae, and budding yeasts.
How is C. albicans treated?
Nystatin for oral thrush, topical agents or fluconazole for localized infections, fluconazole or amphotericin for systemic infections
Describe the morphology of Aspergillus:
Monomorphic fungus with septate hyphae and dichotomous acute-angle branches
What diseases does Aspergillus cause?
Allergic bronchopulmonary aspergillosis, aspergilloma (fungus ball that develops in preexisting lung cavity), and invasive aspergillosis
Describe the morphology of Cryptococcus neoformans:
Encapsulated monomorphic fungus which forms a narrow-based bud
What is the most important disease caused by Cryptococcus?
Meningitis. Most common cause of meningitis in AIDS patients (up to 10% of all AIDS patients)
How are cryptococcal infections diagnosed?
Latex particle agglutination or India ink
finding of budding yeasts with capsules
What radiographic finding can be found with cryptococcal meningoencephalitis?
Hydrocephalus. Also associated with in- creased opening pressure and may require shunt placement
Where is Cryptococcus found in the environment?
Bird (especially pigeon) droppings
What is the treatment of choice for cryptococcal meningoencephalitis?
Intravenous amphotericin B plus flucytosine for 2 weeks is the treatment of choice to sterilize the cerebrospinal fluid (CSF). Long-term maintenance therapy with oral fluconazole may be required for patients with underlying immunosuppression (eg, AIDS, bone marrow transplant).
What genera of fungi most commonly cause zygomycosis (mucormycosis)?
Mucor or Rhizopus
What are the important risk factors for zygomycosis?
Diabetes, especially diabetic ketoacidosis (DKA), iron chelation therapy, neutropenia, immunosuppressive therapies
Why are diabetics and patients on iron chelation therapy more susceptible to zygomycosis?
Rhizopus has a ketone reductase that allows it to flourish in acidic high glucose environments such as DKA. Deferoxamine, an iron chelator, facilitates iron uptake by Rhizopus and thus encourages its growth.
What are the most common body sites for zygomycosis?
Rhinocerebral and thoracic (pulmonary)
Mucor and related species are angioinvasive and contribute to extensive tissue necrosis and infarction. What is the treatment for zygomycosis?
Early surgical debridement with amphotericin B. Prognosis remains poor for both patients with rhinocerebral (mortality 25%-50%) and pulmonary (mortality up to 80%) infections.
What does Rhizopus look like on wet mount?
Large, nonseptate branching hyphae with greater than 90° angles
What is Pneumocystis pneumonia (PCP)?
Pneumocystis pneumonia, an AIDS-defining illness, caused by P. jiroveci. Up to 75% of AIDS patients eventually develop this disease. Note that older sources may still refer to P. carinii, but human disease is caused by P. jiroveci.
What type of cells do P. jiroved attack?
Type I pneumocytes (large, thin cell in- volved in gas exchange and unable to replicate) causing excessive replication of type II pneumocytes (granular cell involved in surfactant secretion and capable of replication)
How is P. jiroved diagnosed?
Fluorescent antibody, silver-stained cysts in bronchial alveolar lavage, or biopsy
What is the treatment for P. jiroved pneumonia?
Trimethoprim-sulfamethoxazole (TMP- SMX). If resistant or allergic, aerosolized pentamidine is an alternative.
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