Mycology Flashcards
What are the systemic mycoses (4)?
Histoplasmosis, Blastomycosis, Coccidioidomycosis, Paracoccidioidomycosis
What disease can the systemic mycoses all cause?
Pneumonia.
Can all disseminate (hence the name, systemic mycoses)
What is a common morphological trait among the systemic mycoses?
Thermal dimorphism -
Cold (20°C) = mold
Hot (37°) = yeast
Exception: Coccidioidomycosis, which is a spherule in tissue.
What is the treatment for local and disseminated infection with the systemic mycoses?
Fluconazole or itraconazole for local infection.
Amphotericin B for systemic infection
What disease can systemic mycoses mimic?
Can mimic TB (granuloma formation)
But NO person to person transmission!
A patient who recently traveled to the Mississippi and Ohio River valleys presents with pneumonia.
Blood smear shows macrophages filled with an organism.
Culture grows dimorphic fungi.
Diagnosis?
What is the source of infection?
Histoplasmosis.
Histo hides (within macrophages). Organisms smaller than RBCs.
Bird or bat droppings
Dimorphic fungi causing pneumonia from mississippi or ohio river valleys.
A patient from Michigan presents with Pneumonia and granulomatous nodules on the skin.
A biopsy of the skin (shown below) finds a broad-based budding fungi that is similar in size to a RBC.
Culture shows a thermally dimorphic fungi.
Blastomycosis
Blasto buds broadly.
States east of Mississippi river and Central America.
Inflammatory lung disease and disseminates to skin and bone. Forms granulomatous nodules.
Patient from California presents after an earthquake with pneumonia and meningitis.
Culture of the CSF shows spherules filled with endospores.
Coccidioidomycosis.
From Southwestern United States, California.
Coccidio crowds
“(San Joaquin) Valley fever”
“Desert bumps” = erythema nodosum
“Desert rheumatism” = arthralgias
A patient from Latin America presents with pneumonia.
Biopsy shows budding yeast with “captain’s wheel” formation that are much larger than RBCs.
Culture shows a thermally dimorphic fungi.
Paracoccidioidomycosis
From Latin America.
_Para_coccidio _para_sails with the _Captain’s_ _wheel_ all the way from _Latin_ _America_.
Patient presents with hyper and hypopigmented skin patches.
A KOH stain shows organisms with a “spaghetti and meatballs” appearnce.
Tinea versicolor
Caused by fungus Malassezia furfur
Occurs in hot, humid weather. Degradation of lipids produce acids that damage melanocytes and cause hyper and hypopigmented patches.
Organisms have a “Spaghetti and meatball” appearance.
How would you treat a Tinea versicolor infection?
Organism: Malassezia furfur
Give topical miconazole, selenium sulfide.
What organism causes athlete’s foot, Jock itch, ringworm on body, ringworm on scalp, and onchomycosis?
Other tinea species - named based on location.
Tinea pedis = foot
Tinea cruris = groin
Tinea corporis = ringworm on body
Tinea capitis = ringworm on head/scalp
Tinea unguium = onchomycosis (fingernail).
Patient presents with an itchy lesion with central clearing resembling a ring.
KOH prep shows mold hyphae, but the fungus is not dimorphic.
What organisms could this be?
Description classic for dermatophytes.
Microsporum, Trichophyton, Epidermophyton
Patient presents with easily scrapable oral leukoplakia.
Candida albicans. Alba = white.
Systemic or superficial fungal infection.
What are the diseases Candida albicans can cause?
Predisposing factors for each?
Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS).
Vulvovaginitis (diabetes/antibiotics)
Diaper rash
Endocarditis (IV drug use)
Disseminated (any organ)
Chronic mucucutaneous candidiasis
How do you treat Candida albicans?
Topical azole for vaginal
Fluconazole/caspofungin for oral/esophageal
Fluconazole, amphotericin B, or caspofungin for systemic.
How does Candida albicans appear on microscopy?
Dimorphic yeast -
20°C Pseudohyphae and budding yeasts
37°C Germ tubes
A patient with a history of TB presents with worsening respioratory symptoms.
A sputum sample shows septate hyphae that branch at 45° angles.
Diagnosis?
Aspregillus fumigatus
Causes invasive aspergillosis in immunocompromised/chronic granulomatous disease.
Allergic bronchopulmonary aspergillosis: Asthma and cystic fibrosis - bronchiectasis and eosinophilia.
Aspergillomas in lung cavities after TB infection.
Think A for Acute Angles in Aspergillus. Not dimorphic.
Patient presents with hepatocellular carcinoma.
What fungal-produced toxin is associated with HCC?
Aflatoxins - some species of Aspergillus.
Immunocompromised patient presents with meningitis.
CT shows “soap bubble” lesions in the brain.
How would you stain this organism?
Cryptococcus neoformans
Stains with India ink and mucicarmine.
Heavily encapsulated yeast, not dimorphic. Found in soil, pidgeon droppings.
What media is required to culture Cryptococcus neoformans?
Sabouraud agar
What’s a specific test for Cryptococcus neoformans?
Latex agglutination test - detects polysaccharide capsular antigen.
A patient in diabetic ketoacidosis presents with headache, facial pain, and black necrotic eschar on the face.
An sample of the organism shows irregular, broad, nonseptate hyphae branching at wide angles.
Diagnosis?
Mucor and Rhizopus species.
Mucor: Disease mostly in ketoacidotic diabetes and leukemic patients. Fungi proliferate in blood vessel walls when there is excess glucose or ketone.
Penetrate cribiform plate and enter brain.
Rhinocerebral, frontal lobe abscesses. May have cranial nerve involvement.
What is the treatment for mucormycosis?
Amphotericin B
An immunocompromised patient presents with pneumonia with a diffuse bilateral CXR appearance.
Culture shows disc-shaped yeast on methenamine silver stain of lung tissue.
Diagnosis?
Pneumocystic jirovecii causing pneumocystis pneumonia (PCP)
Caused by inhaling yeast, symptomatic when immunocompromised.
What are some prophylactic/treatment measures for Pneumocystis?
When should they be done in an AIDS patient?
TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone (prophylaxis only).
Start prophylaxis when CD4 count drops < 200cells/mm3
Patient presents with a pustule where he had been pricked by a thorn.
Microscopy shows cigar-shaped budding yeast.
Sporothrix schenckii causing Sporotrichosis.
A dimorphic cirag-shaped budding yeast that lives on vegetation. Traumatic introduction to skin (“rose gardener’s disease”)
Forms pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis).
What is the treatment for Sporotrichosis?
Treatment: Itraconazole or potassium iodide. (Rose gardener’s disease)
“Plant a rose in the pot.”
Name the opportunistic fungal infections.
- Candida albicans*
- Aspergillus fumigatus*
- Cryptococcus neoformans*
- Mucor* (and Rhizopus)
- Pneumocystic jirovecii*
- Sporothrix schenckii*
