Clinical Microbiology and Infectious Diseases

The Mycoses

Most clinical microbiology labs will not routinely identify Cryptococcus isolates to the species level. Although cultures may take up to a week to become positive, Cryptococcus spp. grow on most clinical media, including standard radiometric blood culturing systems. However, in the diagnosis of pulmonary disease, both the sensitivity and specificity of cultures of respiratory secretions are questionable.As previously described, imaging of the chest by plain radiograph and CT is not diagnostic. Isolated or multiple nodules, pulmonary masses, lobar consolidation, cavitary lesions, pleural effusion, diffuse interstitial infiltrates, and adult respiratory distress–like appearance have all been described with pulmonary cryptococcosis. If signs of increased intracranial pressure or other signs suggestive of CNS infection are present, magnetic resonance imaging or CT of the head to rule out hydrocephalus and cryptococcomas is indicated.Given the limitations of noninvasive methods, invasive procedures are often necessary to confirm the diagnosis of Cryptococcus’s, especially when involvement is limited to the lungs. Either fine-needle aspiration or biopsy may be required to confirm the diagnosis. When pleural effusions are present, cultures of thoracentesis fluid are positive in about 40% of AIDS patients