Opportunistic Infection & Saprophytic Fungus

• Predisposing factors for opportunistic mycoses:
• Aspergillosis caused by Aspergillus fumigatus, Aspergillus niger, and Aspergillus flavus is rare but common in immunocompromised individuals
• Yeast - Candidiasis caused by Candida sp. is common
• Zygomycosis (Mucormycosis) caused by Rhizopus and Mucor is rare but common in immunocompromised individuals
• Yeast - Cryptococcosis caused by Cryptococcus neoformans and Cryptococcus gattii is rare but common in endemic areas with susceptible populations
• Characteristics of opportunistic infection with saprophytic fungi:
• Pneumocystis Pneumonia caused by Pneumocystis jirovecii (formerly Pneumocystis carinii) is rare but common in AIDS patients
• They are normally inhaled as airborne conidia
• Saprophytic fungi live on dead and decaying matter
• They are part of the normal flora of the skin and respiratory tract
• Repeated isolation is needed to consider them significant
• They are inhibited by cycloheximide
• They show rapid growth within 1-5 days
• Molds normally considered environmental contaminants:
• Zygomycetes (Phycomycetes) are sparsely septate and hyaline, including Absidia, Mucor, Rhizopus, Syncephalastrum, and Cunninghamella
• Hyaline molds are septate with transparent hyphae, including Acremonium, Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Chrysosporium, Fusarium, and more
• Order of Zygomycosis:
• Dematiaceous fungi have septate dark-colored hyphae, including Alternaria, Cladosporium, Aureobasidium, Curvularia, and more
• Mucorales and Entomophthorales are involved
• Entomophthorales have 2 families with pathogenic isolates causing subcutaneous and cutaneous infections in immunocompetent children
• Mucorales have all 6 families containing genus and species isolates causing cutaneous and deep infections in immunocompromised individuals
• Rhinocerebral zygomycosis:
• Begins in paranasal sinuses and spreads to orbit, face, palate, or brain
• High risk in patients with DKA, leukemia, organ transplant recipients
• Most common clinical form with a 67% death rate if not treated quickly
• Early diagnosis is critical with black necrotic lesions and purulent drainage
• Pulmonary zygomycosis:
• Usually diagnosed upon autopsy and commonly found in leukemic patients
• Symptoms include bronchitis, pneumonia, thrombosis, lung necrosis, cavitation, and hemoptysis
• Fatal within 2 to 3 weeks with an 83% death rate
• Gastrointestinal zygomycosis:
• Difficult to distinguish from Aspergillosis
• Can lead to death from bowel infarction, sepsis, or hemorrhagic shock
• Most common site of infection is the brain with abscess formation and infarction
• Rare finding usually diagnosed upon autopsy
• High risk in malnourished infants, children, leukemia, or lymphoma patients
• Follows any of the 4 types of zygomycosis and is most common in neutropenic patients with pulmonary infections
• Disseminated zygomycosis:
• Lesions in the stomach, colon, ileum with symptoms of abdominal pain, peritonitis, and intestinal perforation
• Fatality rate is 100% and is diagnosed upon autopsy