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Questions and Answers
What is the primary site of infection for Paracoccidioides brasiliensis?
What is the primary site of infection for Paracoccidioides brasiliensis?
What is the characteristic of the yeast form of Paracoccidioides brasiliensis?
What is the characteristic of the yeast form of Paracoccidioides brasiliensis?
What is the most effective treatment for severe cases of blastomycosis?
What is the most effective treatment for severe cases of blastomycosis?
What is the characteristic of the cultivation of Paracoccidioides brasiliensis in its mold form?
What is the characteristic of the cultivation of Paracoccidioides brasiliensis in its mold form?
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What is the duration of treatment for confined lesions of blastomycosis with itraconazole?
What is the duration of treatment for confined lesions of blastomycosis with itraconazole?
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What is the primary demographic affected by Paracoccidioidomycosis?
What is the primary demographic affected by Paracoccidioidomycosis?
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What is the purpose of cultivating the fungal agent at 37°C?
What is the purpose of cultivating the fungal agent at 37°C?
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What is the common characteristic of the initial lesions of Paracoccidioidomycosis and Blastomycosis?
What is the common characteristic of the initial lesions of Paracoccidioidomycosis and Blastomycosis?
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What is the limitation of serologic tests in the diagnosis of Blastomycosis?
What is the limitation of serologic tests in the diagnosis of Blastomycosis?
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Study Notes
Coccidioidomycosis
- Titers above 1:32 indicate dissemination, and a decline in titers during treatment suggests improvement.
- In AIDS patients, serologic tests are often negative.
- Coccidioidin and spherulin are antigens that elicit positive delayed skin reactions in infected people.
- The coccidioidin skin test reaches maximum induration (≥5 mm in diameter) between 24 and 48 hours after cutaneous injection.
- A negative skin test in patients with disseminated disease implies a poor prognosis.
- Symptomatic primary infection is self-limited and requires only supportive treatment, but itraconazole may reduce symptoms.
- Severe disease requires treatment with amphotericin B, followed by oral therapy with itraconazole.
- Coccidioidal meningitis can be treated with oral fluconazole.
Histoplasmosis
- Histoplasma capsulatum is a dimorphic soil saprophyte that causes histoplasmosis, the most prevalent pulmonary fungal infection.
- Small ovoid cells can be observed within macrophages in histologic sections or in Giemsa-stained smears of bone marrow or blood.
- Specimens are cultured in rich media, such as glucose-cysteine blood agar at 37°C and on SDA or IMA at 25–30°C.
- Cultures must be incubated for a minimum of 4 weeks.
- CF tests for antibodies to histoplasmin or yeast cells become positive within 2–5 weeks after infection.
- CF titers rise during progressive disease and decline to low levels when the disease is inactive.
- A CF titer ≥ 1:32 indicates progressive disease.
- Enzyme immunoassay for circulating polysaccharide antigen is a sensitive test.
- The histoplasmin skin test becomes positive soon after infection and remains positive for years.
- Acute pulmonary histoplasmosis is managed with supportive therapy and rest.
- Itraconazole is the treatment for mild to moderate infection.
- Disseminated disease requires systemic treatment with amphotericin B.
Blastomycosis
- Blastomyces dermatitidis is a thermally dimorphic fungus that grows as a mold in culture, producing hyaline, branching septate hyphae and conidia.
- At 37°C or in the host, it converts to a large, singly budding yeast cell.
- Colonies develop within 2 weeks on Sabouraud’s or enriched blood agar at 30°C.
- Identification is confirmed by conversion to the yeast form after cultivation on a rich medium at 37°C.
- Serologic tests are not as useful for the diagnosis of blastomycosis as they are in other endemic mycoses.
- Severe cases are treated with amphotericin B.
- Confined lesions can be treated with a 6-month course of itraconazole.
Paracoccidioidomycosis
- Paracoccidioides brasiliensis is the thermally dimorphic fungal agent of paracoccidioidomycosis, confined to endemic regions of Central and South America.
- Cultures of the mold form grow very slowly and produce chlamydospores and conidia.
- At 36°C, on rich medium, it forms large, multiply budding yeast cells.
- P brasiliensis is inhaled, and initial lesions occur in the lung.
- After a period of dormancy, pulmonary granulomas may become active, leading to chronic, progressive pulmonary disease or dissemination.
- Most patients are 30–60 years old, and over 90% are men.
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Description
Test your knowledge on the diagnosis and treatment of coccidioidomycosis, a fungal disease caused by Coccidioides immitis. Learn about the serologic tests and skin tests used to identify the infection and monitor treatment progress. Covers important concepts in medical microbiology and infectious diseases.
