Fungi Structure and Growth

Fungal Infections

• Coccidioidomycosis is caused by Coccidioides immitis and can be symptomatic or asymptomatic, also known as Valley Fever.
• It is restricted to certain geographical areas and occurs through inhalation of arthroconidia.
• The fungal outer wall has antiphagocytic properties, preventing elimination.
• Disseminated coccidioidomycosis can occur in patients with AIDS and those on immunosuppressive therapy.

Blastomycosis

• Blastomycosis is caused by Blastomyces dermatitidis and primarily affects the lungs.
• Spores of the fungi enter through the respiratory system and can spread through the bloodstream to affect other parts.
• Men between 20 and 40 years old are most commonly infected.
• Blastomycosis is not increased in AIDS patients.

Pneumocystis Pneumonia (PCP)

• PCP is a lethal pneumonia common in AIDS patients, caused by Pneumocystis (carinii) jiroveci.
• It is never been grown in culture, and most information comes from clinical observations.

Candida albicans

• Candida albicans is a yeast that forms pseudohyphae and hyphae when it invades tissue.
• It can cause thrush, disseminated candidiasis, and chronic mucocutaneous candidiasis.
• Transmission is rare, but can cause pneumonia, resulting in fever, coughing, difficulty breathing, and tachypnea.
• Laboratory diagnosis involves microscopic examination of tissue, revealing yeasts and pseudohyphae.

Cryptococcus neoformans

• Cryptococcus neoformans is a heavily encapsulated yeast that causes cryptococcosis, especially cryptococcal meningitis.
• It is found in soil, enriched by pigeon droppings, and transmission occurs through inhalation of airborne yeast cells.

Aspergillus fumigatus

• Aspergillus fumigatus is a mold that causes invasive aspergillosis, allergic bronchopulmonary aspergillosis, and aspergilloma (fungus ball).
• It is found in soil and transmission occurs through inhalation of airborne spores (conidia).

Basic Mycology

• Fungi are eukaryotic organisms that exist in two basic forms: yeasts and molds.
• Yeasts are single cells that reproduce by budding, while molds consist of long filaments of cells called hyphae and reproduce by cell division.
• Some fungi are dimorphic, existing as yeasts or molds depending on temperature.

Factors of Fungal Infection

• Two major factors govern the incidence and spread of fungal infection: ubiquity of infectious organisms and adaptive immune response.
• Immunocompromised patients are at much greater risk of fungal infection.

Histoplasmosis

• Histoplasmosis is caused by Histoplasma capsulatum and occurs in soil contaminated with bat or bird droppings.
• It is commonly found in temperate, subtropical, and tropical zones, and 50% - 90% of residents in these areas test positive for exposure.
• People who live and work in the vicinity of bat or bird droppings are at increased risk of infection.
• Amphotericin B is the treatment of choice if necessary.