Mycology Flashcards
How do Mucor and Rhizopus enter the body?
Via inhalation of spores
What is the clinical name for dermatophyte (cutaneous fungal) infections?
Tinea (dermatophytes)
How does Pneumocystis pneumonia appear on methanamine-stained samples?
Disc-shaped yeasts
What 2 stains are used to diagnose Cryptococcus neoformans?
India ink (shows clear halo) and mucicarmine (shows inner red capsule)
What disease is caused by Pneumocystis jirovecii?
Pneumocystis pneumonia (PCP), which is a diffuse interstitial pneumonia
What structure must Mucor and Rhizopus penetrate to invade the brain?
Cribriform plate
A man with diabetes mellitus has a headache, facial pain, a black necrotic facial eschar, and cranial nerve palsies. What is the likely diagnosis?
Cavernous sinus thromboses leading to cranial nerve involvement, a complication of Mucor and Rhizopus infections
An athlete has hypopigmented and hyperpigmented macules on her back after intensive summer training. What is the most likely diagnosis?
Tinea (pityriasis) versicolor (Malassezia spp, Pityrosporum spp)
An immunocompromised patient presents with “soap bubble” lesions in his brain on imaging. How does an infection with Cryptococcus neoformans lead to this?
Through hematogenous dissemination after inhalation
What are the 3 different manifestations of tinea pedis?
Moccasin distribution, vesicular type, and interdigital (most common)
A male patient, positive for HIV, has an infection with a heavily encapsulated, nondimorphic yeast. What is the likely diagnosis?
Cryptococcus infection
What are the various prophylaxis options for Pneumocystis pneumonia?
Trimethoprim-sulfamethoxazole (TMP-SMX), dapsone, pentamidine, or atovaquone
How can tinea corporis be acquired?
From contact with infected pets or farm animals
How does Sporothrix schenckii exist in the human body and in the soil?
Cigar-shaped yeast in the human body at 37°C; hyphae with spores in soil (conidia); S schenckii is dimorphic
Where are the abscesses in Mucor and Rhizopus infections most commonly found?
Rhinocerebral and frontal lobes
You culture Cryptococcus neoformans at 25°C and then at 37°C. What morphology do you note?
C neoformans grows as a yeast at both temperatures (it is not dimorphic)
What is observed when Candida albicans is grown at 20°C and then at 37°C?
Forms pseudohyphae and budding yeast at 20°C; germ tube formation at 37°C
How do you treat disseminated candidiasis?
Amphotericin B, fluconazole, or echinocandins
How is Pneumocystis pneumonia diagnosed?
From a bronchoalveolar lavage or lung biopsy; sample stained with methenamine silver or identified with a fluorescent antibody
At what CD4+ count should patients who are HIV+ begin to receive prophylaxis against Pneumocystis pneumonia?
< 200 cells/mm3
What populations are more likely to develop invasive aspergillosis?
Patients who are immunocompromised and those with disorders of neutrophil dysfunction (ie, chronic granulomatous disease)
What is the first-line treatment for oral thrush alone?
Treatment for superficial Candida infections is nystatin, fluconazole, or echinocandins
What class of organisms causes tinea pedis, cruris, corporis, capitis, and unguium?
Dermatophytes (representative geni include Microsporum, Trichophyton, Epidermophyton)
Which population is at an increased risk of developing vulvovaginitis due to Candida albicans?
Patients with diabetes and those using antibiotics
What treatment options are available for Aspergillus infections?
Voriconazole, echinocandins (2nd line)
How does tinea versicolor cause hypopigmentation on skin?
Lipid degradation by Malassezia spp (Pityrosporum spp) produces acids → inhibit tyrosinase (melanin synthesis) → hypopigmentation
What opportunistic fungus is a cause of endocarditis in IV drug users?
Candida albicans
Name 3 infections caused by Cryptococcus neoformans typically found in immunocompromised patients.
Cryptococcosis, cryptococcal encephalitis (“soap bubble” lesions in the brain), and cryptococcal meningitis
A gardener presents with a pustule on her forearm and multiple nodules tracing upward toward her axilla. What is the most likely diagnosis?
Sporotrichosis (rose gardener’s disease)
How does Aspergillus fumigatus appear on culture media at 37°C?
45° branching septate hyphae (broom-like appearance)
Which group of hosts would be symptomatic if infected with Pneumocystis?
Immunocompromised patients (eg, those with AIDS); otherwise, most are asymptomatic
What part of the body is affected in a tinea unguium infection?
Nails (fungal nail infection is also termed onychomycosis)
What is the appearance of Pneumocystis pneumonia on chest imaging?
Diffuse, bilateral ground-glass opacities with pneumatoceles
What is the treatment of tinea (pityriasis) versicolor?
Selenium sulfide, topical and/or oral antifungal medications
A man has multiple erythematous scaling rings with central clearing. What is the most likely diagnosis?
Tinea corporis infection (ringworm)
What populations are at high risk for oral/esophageal thrush?
Immunocompromised: neonates, patients with diabetes and AIDS, chronic steroid users
How is sporotrichosis transmitted?
Introduction of fungal spores into the skin after an injury, often caused by thorns (hence, rose gardener’s disease)
What is the treatment for vaginal candidiasis?
Oral fluconazole/topical azoles
An immunosuppressed pigeon keeper has meningitis. Mucicarmine stains of the CSF culture results are shown (image). What might brain imaging show?
“Soap bubble” lesions on brain imaging from concomitant encephalitis (diagnosis: Crytococcus neoformans; note the red inner capsule on mucicarmine)
A patient has had frequent outbreaks of white plaques in his mouth (image) for his entire life. What is a possible diagnosis?
Chronic mucocutaneous candidiasis as the underlying cause of Candida albicansoral thrush
A patient with asthma presents with the CT findings (image), and a diagnosis of allergic bronchopulmonary aspergillosis is made. What is the pathophysiology of this condition?
Patients with asthma or cystic fibrosis have a hypersensitivity response to aspergillus colonization
What organism is shown in this image?
Malassezia spp (Pityrosporum spp); shows “spaghetti and meatball” appearance on microscopy
Which patient populations are most susceptible to disease with the fungal organism pictured (image)?
Mucor and Rhizopus are most worrisome in patients with diabetic ketoacidosis or neutropenia (eg, leukemia)
A patient presents with lymphadenopathy and the findings in the image below. What is the likely diagnosis?
Tinea capitis (note alopecia and scaling in the image)
A patient presents with foot discoloration (image) and is thought to have a fungal skin infection. What is the most likely diagnosis?
This is tinea pedis, with a moccasin distribution (dermatophyte infection)
The cerebrospinal fluid of a male with meningitis who is positive for HIV shows a fungus (image). At what temperature has this fluid specimen likely been analyzed?
This is Candida albicans, a white (“alba”) dimorphic yeast that exhibits pseudohyphae and budding yeasts at 20°C, as shown in the image (germ tubes would be seen at 37°C)
A transplant patient develops fever and dyspnea. Bronchoalveolar lavage with methenamine staining of the sample is shown (image). What findings would be seen on a chest CT?
Diffuse, bilateral ground-glass opacities with pneumatoceles (air-filled cysts); this is Pneumocystis pneumonia
A patient with cystic fibrosis has a fungal culture that shows the following. What is the diagnosis?
Infection with Aspergillus fumigatus, causing allergic bronchopulmonary aspergillosis (ABPA); note conidia in radiating chains at the ends of conidiophores
A patient complains of itching in her inguinal area (image). No central clearing is present. Diagnosis?
Tinea cruris
A man presents with pruritic lesions (see image) on his extremities. What is the likely diagnosis?
Tinea corporis (note the patches with central clearing in image)
A gardener has an arm pustule with ascending lymphangitis (image). What is the diagnosis?
Sporotrichosis
A chest x-ray (image) is shown of a patient with AIDS who is short of breath. A lung biopsy and methenamine silver staining of tissue reveals disc-shaped yeast. Diagnosis?
Pneumocystis pneumonia
A fungal organism is stained with India ink (image). What additional stain, targeting an inner capsule, could help to confirm the diagnosis?
A mucicarmine stain, which highlights the inner capsule as red (diagnosis: Cryptococcus neoformans; note the “clear halo” appearance)
Light microscopy of a KOH prep with blue fungal stain reveals the following (image). What is the organism?
Dermatophytes (tinea infection)
A patient presents with the itchy lesion shown in the image. What would a KOH preparation of a sample taken from the lesion demonstrate?
Branching septate hyphae; this is tinea pedis (with interdigital presentation, which is most common)
A CT of the chest in a patient with AIDS, acute-onset dyspnea, and hypoxia is shown (image). What diagnostic testing can identify the causative organism?
Bronchoalveolar lavage or lung biopsy; this is Pneumocystis pneumonia (note the presence of pneumatoceles with interstitial pneumonia)
A patient with chronic granulomatous disease is superinfected with the organism shown in the image. Name 3 presentations of this infection.
Allergic bronchopulmonary aspergillosis (ABPA), lung cavity aspergillomas, and invasive aspergillosis (note Acute Angles in Aspergillosis)
Light microscopic findings of a fungal culture grown at 37°C are shown (image). What is the organism?
Candida albicans
A patient develops recurrent fungal infections every summer with the rash shown (image). What characteristic pattern of this lesion would be seen on microscopy?
Spaghetti and meatball pattern (diagnosis: tinea versicolor)
A patient presents with pancytopenia, splenomegaly, and palatal ulcers. A bone marrow biopsy is done and the image below shows the results. What is the likely diagnosis?
Histoplasmosis
What is the size of this organism relative to that of an RBC (image)?
Larger than an RBC (this is the characteristic “captain’s wheel” of paracoccidioidomycosis)
What systemic mycoses has the following histopathology (image)?
Histoplasma; this is a macrophage filled with Histoplasma organisms
What systemic mycoses is characterized by the following histopathology (image)?
Blastomycosis (“Broad-based budding: Blasto buds broadly”)
What systemic mycosis (histopathology below) can present with meningitis and pneumonia?
Coccidioidomycosis
