Lecture 9: Medically Significant Fungi Flashcards
How are pathogenic fungi classified based on growth form?
Yeasts (e.g., Candida): Unicellular, reproduce by budding.
Moulds (e.g., Aspergillus): Multicellular, filamentous hyphae, produce spores.
Dimorphic: Switch between yeast (body) and mould (environment).
What makes C. auris a critical pathogen?
Resistance: Pan-resistant to azoles, amphotericin B; 1st-line echinocandins.
Transmission: Nosocomial, colonizes skin, survives on surfaces.
At-risk groups: Immunocompromised, ICU patients, diabetics.
How is C. auris identified in the lab?
Culture: CHROMagar™ (light blue colonies with halo).
Microscopy: Gram-positive yeast, germ tube-negative (vs. C. albicans).
MALDI-TOF: Gold standard for species confirmation.
Name 3 clinical syndromes caused by A. fumigatus.
Allergic bronchopulmonary aspergillosis (ABPA): Hypersensitivity in asthma/CF.
Invasive aspergillosis: Disseminated infection in immunocompromised.
Aspergilloma: Fungal ball in pre-existing lung cavities.
What non-culture methods detect Aspergillus?
Galactomannan ELISA: Serum/BAL (60–90% sensitivity).
1,3-β-D-glucan: Broad fungal marker (>80 pg/mL = positive).
PCR: Detects DNA in sputum/BAL.
What organisms cause ringworm, and how is it diagnosed?
Agents: Trichophyton, Microsporum, Epidermophyton.
Diagnosis: KOH mount (septate hyphae), culture (SDA; T. rubrum = wine-red reverse).
Match Tinea types to body sites:
Capitis: Scalp (hair loss, scaling).
Corporis: Body (circular rash).
Pedis: Feet (Athlete’s foot).
Compare treatments for:
Candidemia: Echinocandins (e.g., caspofungin).
Invasive aspergillosis: Voriconazole.
Ringworm: Topical clotrimazole/oral terbinafine.
What samples are used to diagnose:
C. auris: Skin swabs (nose/throat/perineum).
Aspergillosis: Sputum/BAL.
Ringworm: Skin scrapings (lesion edge).
Why is C. auris a public health crisis?
MDR: Limited treatment options.
Persistence: Survives on surfaces, spreads in hospitals.
Misidentification: Labs may confuse with other Candida spp.
