Cryptococcosis other diagnostic studies

Other diagnostic studies helpful for diagnosis of cryptococcal infection include demonstration of the budding yeast on India ink stain, staining the polysaccharide cell wall using mucicarmine stain, detection of cryptococcal antigen in CSF, and a positive culture for Cryptococcus neoformans.

• India ink or fungal wet mount of CSF will demonstrate a budding yeast.
• Mucicarmine stain provides specific staining of the polysaccharide cell wall.
• Antigen detection in CSF is useful for the diagnosis of cryptococcal meningitis.
• Cryptococcus neoformans can be cultured from sputum, bronchoalveolar lavage, transbronchial lung biopsy specimen, pleural fluid, or pleural biopsy specimen in patients with pulmonary cryptococcosis.^[1]

• Culture is the gold standard for diagnosing cryptococcal infection.^[2]
• Blood cultures may be positive in severe infections.

• India Ink can be used on CSF to quickly visualize Cryptococcus cells under a microscope; however, it can have limited sensitivity.^[2]
• Many laboratories in the United States no longer perform this test. ^[3]
• Histopathology for detection of narrow-based budding yeasts in tissue can also be used.^[2]

• Antigen detection can be used on CSF or serum for detection of early, asymptomatic cryptococcal infection in HIV-infected patients.
• It has a higher sensitivity than microscopy or culture.^[2]
• CSF CrAg is usually positive in patients with cryptococcal meningoencephalitis. Serum CrAg is usually positive in both meningeal and non-meningeal infection and may be present weeks to months before symptom onset.^[3]
• A positive serum CrAg should prompt a lumbar puncture to rule out meningeal disease.^[3]
• Techniques used include:^[2]

• Latex agglutination (LA)
• Enzyme immunoassay (EIA)
• Lateral flow assay (LFA)

Cryptococcal meningitis may be differentiated from other causes of meningitis by cerebrospinal fluid examination as shown below:^{[4][5][6][7][8]}

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  Cryptococcosis of lung in patient with AIDS. From Public Health Image Library (PHIL). ^[10]
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  Cryptococcosis of lung in patient with AIDS. Mucicarmine stain. From Public Health Image Library (PHIL). ^[10]
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  Cryptococcosis of lung in patient with AIDS. Methenamine silver stain. From Public Health Image Library (PHIL). ^[10]
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  Micrograph depicts the histopathologic changes associated with cryptococcosis of the spleen. From Public Health Image Library (PHIL). ^[10]
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  Micrograph depicts the histopathologic changes associated with cryptococcosis of an adrenal gland. From Public Health Image Library (PHIL). ^[10]
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  Micrograph depicts the histopathologic changes associated with cryptococcosis of an adrenal gland. From Public Health Image Library (PHIL). ^[10]
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  Micrograph depicts the histopathologic changes associated with cryptococcosis of the lung using GMS stain. From Public Health Image Library (PHIL). ^[10]
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  Micrograph depicts the histopathologic changes associated with cryptococcosis of the lung using Mucicarmine stain. From Public Health Image Library (PHIL). ^[10]
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  Micrograph depicts histopathologic changes due to cryptococcosis of the liver. From Public Health Image Library (PHIL). ^[10]
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  Cryptococcus neoformans fungi from a liver specimen, and stained using the periodic acid-Schiff staining technique (980X mag). From Public Health Image Library (PHIL). ^[10]
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  Methenamine silver-stained photomicrograph of a lung lesion tissue specimen, reveals some morphology associated with the disease cryptococcosis (800X mag). From Public Health Image Library (PHIL). ^[10]
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  Photomicrograph of a lung lesion tissue specimen, reveals some morphology associated with the disease cryptococcosis (800x mag). From Public Health Image Library (PHIL). ^[10]
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  Periodic acid-Schiff-stained photomicrograph revealed some of the histopathologic details associated with a disseminated Cryptococcus sp. infection involving the liver (980x mag). From Public Health Image Library (PHIL). ^[10]