Coccidioidomycosis Diagnosis and Treatment

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.