Fungi & Human disease Flashcards
What are the key characteristics of fungi?
Eukaryotic, heterotrophic (absorb nutrients), non-photosynthetic, can be unicellular (yeasts) or multicellular (molds).
Why are most fungi unable to infect humans?
They cannot evade human immune defenses as humans have innate and adpative immune responses.
Name two superficial fungal infections and their causative agents.
-Athlete’s foot (Trichophyton rubrum),
-Onychomycosis (Trichophyton rubrum).
Which patient populations are at highest risk for invasive fungal infections?
Immunocompromised individuals (HIV/AIDS, chemotherapy, organ transplants, diabetics).
How does Aspergillus fumigatus infect the lungs?
Inhalation of conidia (spores) that germinate into hyphae, secreting toxins (e.g., gliotoxin) and hydrolases.
What is unique about Cryptococcus neoformans virulence?
Thick polysaccharide capsule reduces phagocytosis; can infect the CNS (cryptococcal meningitis)
How does Candida albicans switch from commensal to pathogen?
Morphological switching (yeast-to-hypha) driven by Als3p/Hwp1p adhesins and secretion of candidalysin (a pore-forming toxin).
Why is rhino-cerebral mucormycosis so lethal?
Rapid tissue necrosis due to mucoricin (a ricin-like toxin); mortality ~90% even with treatment.
What is the difference between fungistatic and fungicidal drugs?
-Fungistatic inhibits growth (e.g., azoles);
-Fungicidal kills fungi directly (e.g., polyenes).
How do azoles (e.g., fluconazole) work?
Inhibit ergosterol synthesis by blocking lanosterol demethylase (ERG11).
Why is liposomal amphotericin B less toxic than standard amphotericin B?
Lipid formulation reduces binding to human cell membranes, lowering nephrotoxicity.
What is the target of echinocandins (e.g., caspofungin)?
Inhibit β-1,3-glucan synthase, disrupting fungal cell wall synthesis.
How does 5-fluorocytosine (5-FC) work?
Converted to 5-fluorouracil in fungi, inhibiting DNA/protein synthesis.
A diabetic patient with black necrotic nasal lesions likely has what infection?
Rhino-cerebral mucormycosis (caused by Mucorales).
An HIV patient with headaches and photophobia may have what fungal infection?
Cryptococcal meningitis (diagnose via CSF antigen testing).
Why is Candida auris a global health threat?
Multi-drug resistance, spreads in hospitals, and forms persistent biofilms.
