Pneumocystis Jiroveci Infection

Pneumocystis jiroveci

• Important cause of pneumonia in immunocompromised individuals
• Morphology: appears as a cyst
• Found in domestic animals (horses, sheep) and rodents, with each mammalian species having its own species of Pneumocystis

Life Cycle and Transmission

• Life cycle of Pneumocystis is unclear
• Transmission occurs through inhalation

Infection and Pathology

• Infection primarily occurs in the lungs, inducing an inflammatory response with plasma cells
• Results in a frothy exudate that blocks oxygen exchange, leading to "plasma cell pneumonia"
• Pneumonia occurs when host defenses are reduced, such as with low CD4-positive T cells

Clinical Findings

• Sudden onset of fever
• Nonproductive cough
• Dyspnea and tachypnea
• Bilateral rales and rhonchi are heard on auscultation
• Chest X-ray shows diffuse interstitial pneumonia with "ground glass" infiltrates bilaterally

Extrapulmonary Infections

• Occur in late stages of AIDS, affecting primarily the liver, spleen, lymph nodes, and bone marrow

Mortality and Diagnosis

• Mortality rate of untreated Pneumocystis pneumonia approaches 100%
• Laboratory diagnosis involves:
  • Specimen: lung tissue or fluids obtained by bronchoscopy, bronchial lavage, or open lung biopsy
  • Microscopic examination with methenamine silver or Giemsa stain to identify typical cysts
  • Fluorescent-antibody staining
  • PCR
  • No serologic test available, and the organism cannot be grown in culture

This quiz covers the characteristics and transmission of Pneumocystis jiroveci, a fungus that causes pneumonia in immunocompromised individuals. Learn about its morphology, habitat, and life cycle.