7.1-SYSTEMIC MYCOSIS + COCCIDIOIDOMYCOSIS Flashcards
What are the four primary systemic mycoses?
Histoplasmosis, Blastomycosis, Coccidioidomycosis, Paracoccidioidomycosis
What is the mode of transmission (MOT) for systemic mycoses?
Inhalation of conidia
What fungal structure is associated with virulence in systemic mycoses?
α-glucan in the cell wall
Are systemic mycoses transmissible from person to person?
No
What is the defining characteristic of the fungi that cause systemic mycoses?
Thermally dimorphic
Which systemic mycosis-causing fungi have clearly defined habitats?
Coccidioides (dry soil), Histoplasma (soil mixed with guano)
Which systemic mycosis-causing fungi have poorly defined habitats?
Blastomyces, Paracoccidioides
What are the typical outcomes of systemic mycoses in immunocompetent individuals?
Asymptomatic or self-limiting infection
What are the two causative agents of Coccidioidomycosis?
Coccidioides immitis & Coccidioides posadasii
What are the alternative names for Coccidioidomycosis?
San Joaquin Valley Fever / Desert Rheumatism
Where is Coccidioides immitis primarily found?
California
Where is Coccidioides posadasii primarily found?
Arizona, Texas, South America
What is the tissue form of Coccidioides?
Spherules with endospores (not true yeast)
What does the mycelial phase of Coccidioides look like?
Moist, gray membrane → white cottony aerial mycelium → tan to brown with age
How fast does Coccidioides grow?
5-14 days (arthroconidia in 1-2 weeks)
What is the structure of Coccidioides mycelial phase?
Coarse, septate, branched hyphae with thick-walled barrel-shaped arthroconidia
What alternates between arthroconidia in Coccidioides?
Empty disjunctor cells
What is the structure of Coccidioides yeast phase?
Large, round, thick-walled spherules with endospores
What are the two clinically useful antigens of Coccidioides?
Coccidioidin & Spherulin
What is Coccidioidin derived from?
Liquid mycelial culture filtrate
What is Spherulin derived from?
Broth culture of spherules
What is the most common initial manifestation of Coccidioidomycosis?
Self-limited influenza-like illness
What are the hypersensitivity reactions associated with Coccidioidomycosis?
Rash, erythema nodosum, erythema multiforme
What are risk factors for systemic Coccidioidomycosis?
Heredity, sex (males > females), age, immunosuppression
Which hormones stimulate the growth of Coccidioides?
Estradiol & progesterone
How is Coccidioidomycosis diagnosed histologically?
Granulomas with giant cells & interspersed suppuration
What samples are used to diagnose Coccidioidomycosis?
Sputum, exudates, CSF, blood, urine, tissue biopsy
What is the preferred stain for detecting spherules & endospores?
KOH or calcofluor white stain
What media are used to culture Coccidioides?
Inhibitory mold agar, Sabouraud’s agar, blood agar
Why must cultures be handled in a biosafety cabinet?
Highly infectious arthroconidia
What are confirmatory tests for Coccidioides immitis?
Antigen detection, animal inoculation, DNA probe
What test detects IgM antibodies for Coccidioides?
Latex agglutination test
What tests detect IgG antibodies for Coccidioides?
Immunodiffusion (ID) & Complement Fixation (CF)
What CF antibody titer suggests dissemination?
≥1:32
Why are serologic tests often negative in AIDS patients with Coccidioidomycosis?
Impaired antibody production
What is a positive Coccidioidin skin test?
≥5 mm induration in 24-48 hours
What is the more sensitive alternative to Coccidioidin?
Spherulin
What is the general treatment for self-limited Coccidioidomycosis?
Supportive care
What is the first-line treatment for severe Coccidioidomycosis?
IV amphotericin B → oral itraconazole
What is the treatment for Coccidioidal meningitis?
Oral fluconazole
When is surgical resection necessary?
For pulmonary cavities
Is Coccidioidomycosis communicable from person to person?
No
Do infected rodents contribute to Coccidioides spread?
No evidence
What are control measures to reduce environmental exposure?
Paving roads, planting grass, using oil sprays, reducing dust
What is the mode of transmission (MOT) for systemic mycoses?
Inhalation of conidia
What type of fungi cause systemic mycoses?
Thermally dimorphic fungi
What cell wall component is associated with virulence in systemic mycoses?
α-glucan
Why is Coccidioides sometimes considered not dimorphic?
Unlike Histoplasma, Blastomyces, and Paracoccidioides, which form yeast in tissue, Coccidioides forms spherules instead of yeast.
What are the etiologic agents of coccidioidomycosis?
Coccidioides posadasii
Coccidioides immitis
Where is Coccidioides posadasii primarily found?
Arizona, Texas, and South America.
What is the colonial appearance of Coccidioides?
Moist, gray membranous colony that develops white, cottony aerial mycelium; turns tan to brown with age.
How fast does Coccidioides grow?
Growth rate: 5-14 days.
Arthroconidia may need 1-2 weeks to form.
How is coccidioidomycosis acquired?
Inhalation of arthroconidia
What is the only evidence of infection in many cases?
Development of serum precipitins and conversion to a positive skin test within 2-4 weeks.
What factors increase the risk of systemic coccidioidomycosis?
Heredity, sex (males more susceptible), age, and compromised cell-mediated immunity
Elevated estradiol and progesterone levels stimulate fungal growth
What diagnostic finding confirms coccidioidomycosis?
Presence of spherules with endospores
What specimens are collected for culture?
Sputum, exudate from cutaneous lesions, spinal fluid, blood, urine, and tissue biopsies
What stains help visualize spherules?
KOH stain
Calcofluor white stain
Histologic preparations
What precautions must be taken with suspected Coccidioides cultures?
Must be examined only in a biosafety cabinet
What culture media are used for Coccidioides?
Inhibitory mold agar
Sabouraud’s agar
Blood agar slants (with or without antibiotics and cycloheximide)
What tests confirm the identification of Coccidioides?
Detection of C. immitis-specific antigen
Animal inoculation
Specific DNA probe
What serologic tests detect IgG antibodies?
Immunodiffusion (ID) test
Complement fixation (CF) test
Why are serologic tests often negative in AIDS patients?
Due to impaired antibody response.
What is the treatment for severe coccidioidomycosis?
Intravenous amphotericin B followed by oral itraconazole for months.
What is the drug of choice for coccidioidal meningitis?
Oral fluconazole
What is the etiologic agent of histoplasmosis
Histoplasma capsulatum
Where is Histoplasma capsulatum found in nature?
Avian and bat habitats (guano)
Alkaline soil
What is the geographic distribution of histoplasmosis?
Global
Endemic in:
Ohio, Missouri, and Mississippi River valleys
Central Africa (var. duboisii)
What is the microscopic morphology of Histoplasma capsulatum?
Oval yeasts (2 × 4 µm), intracellular in macrophages
What are the etiologic agents of coccidioidomycosis?
Coccidioides posadasii
Coccidioides immitis
Where is Coccidioides found in nature?
Soil, rodents
What is the geographic distribution of coccidioidomycosis?
Semiarid regions of:
Southwestern United States
Mexico
Central and South America
What is the microscopic morphology of Coccidioides?
Spherules (10–80 µm) containing endospores (2–4 µm)
What is the etiologic agent of blastomycosis?
Blastomyces dermatitidis
Where is Blastomyces dermatitidis found in nature?
Unknown (riverbanks?)
What is the geographic distribution of blastomycosis?
Mississippi, Ohio, and St. Lawrence River valleys
Southeastern United States
What is the microscopic morphology of Blastomyces dermatitidis?
Thick-walled yeasts with broad-based, usually single, buds (8–15 µm)
What is the etiologic agent of paracoccidioidomycosis?
Paracoccidioides brasiliensis
Where is Paracoccidioides brasiliensis found in nature?
Unknown (soil?)
What is the geographic distribution of paracoccidioidomycosis?
Central and South America
What is the microscopic morphology of Paracoccidioides brasiliensis?
Large, multiply budding yeasts (15–30 µm)
