02/27g Introduction to Mycology Flashcards
What are fungi? List five characteristics, especially things that distinguish them from animals and plants
1) Eukaryotic
2) Non-photosynthetic (require a carbon source)
3) Have a cell wall
4) Cell membranes contains ergosterol
5) Often grow as yeasts (round) or moulds (filamentous)
List the seven most common pathogenic fungal genera
1) Candidia
2) Aspergillus
3) Cryptococcus
4) Blastomyces
5) Histoplasma
6) Coccidioides
7) Dermatophytes
What has there been an increased overall incidence of fungal infection?
More immunosuppressed and “at risk” patients (HIV, steroids, transplants, ICU patients)
Travel
What are the four medical problems caused by fungi?
1) Allergic disease
2) Mushroom poisoning (such as amanita)
3) Mycotoxin - poisoning by secondary metabolites
4) Mycoses
What are mycoses?
Infection and resulting disease caused by fungi
What four types of fungi cause mycoses?
Yeasts
Moulds
Thermally dimorphic fungi
Dermatophytes
What is the most common disease-causing yeast?
Candida albicans
What two fungi are common colonizers of humans?
C. albicans
Dermatophytes
What is mucosal candidiasis?
Locally invasive disease caused by C. albicans
Infects oral and vaginal mucosa in immunocompetent patients
Infects oral and esophageal mucosa in immunocompromised patients
What are three manifestations of systemic candidiasis?
Candidemia (from IV catheters) Intra-abdominal (abdominal surgery) Disseminated disease (immunocompromised patients)
What are three other Candida species that commonly cause infections, particularly in hospitals?
C. glabrata
C. krusei
C. parapsilosis
What is Cryptococcosis?
An opportunistic infection by Cryptococcus neoformans
Causes a primary pulmonary infection with CNS tropism
Most pulmonary infections are self-limiting, but CNS disease is fatal if untreated
How is Cryptococcosis diagnosed?
Culture
Lumbar puncture
Antigen tests for capsular polysaccharide
Where in the environment is Cryptococcus neoformans often found?
Bird excreta
Decaying vegetation
Free-living amoebae
What are the two forms of infectious moulds?
Septate
Aseptate (Zygomycetes)
What are the two types of infectious septate moulds?
Non-pigmented/hyaline
Pigmented/dematiaceous
What are four genera of hyaline moulds?
Aspergillus
Fusarium
Scedosporium-Pseudallescheria
Paecilomyces
What is the most common Aspergillus species that causes human disease?
A. fumigatus
What are two diagnostic morphological features of Aspergillus?
Uniform hyphal diameter
Regular, frequent septa
In which patient population is Aspergillosis a major concern?
Very immunosuppressed patients, particularly those who are neutropenic
How does Aspergillus enter the body? Where does it cause disease?
Entry via the respiratory tract
Disseminates to all organs and the CNS
How is Aspergillosis diagnosed? List three ways
Chest X-ray
Histopathology
Galactomannan detection
How is Aspergillosis treated?
Empiric antifungals
Pre-emptive monitoring is the most effective way to prevent infection
What are four types of diseases that are caused by dematiaceous fungi? Name examples
Superficial - tinea nigra, black piedra
Cutaneous and corneal - mycotic keratitis, onychomycosis
Subcutaneous - by traumatic inoculation
Systemic - infects lungs in immunocompromised patients and spreads to other organs, particularly the CNS
What are Zygomycetes? What do they look like?
Bread moulds
Have no septa and filaments have variable diameters
What are the two most common disease-causing genera of Zygomycetes?
Mucor
Rhizopus
With what three conditions is it common to see Mucormycosis?
Hematologic malignancy
Diabetic ketoacidosis
Iron overload syndromes
What are the clinical manifestations of Mucormycosis?
Rhinocerebral
Pulmonary
Disseminated
How is Mucormycosis treated?
Surgical excision - very important to do
High dose antifungals
Reconstitute immune system
What are three species of thermally dimorphic fungi that are common to the US? In what geographical regions are they found?
Histoplasma capsulatum - central US (Ohio and Mississippi River valleys)
Blastomyces dermatitidis - central and eastern US, especially the Great Lakes region
Coccidioides immits - arid desert regions of the southwest US and Latin America
What does it mean if a fungi is “thermally dimorphic”?
It exists in the environment as a mould, and in humans as a round/yeast-like form
Morphological transition between the two forms depends on temperature
How are thermally dimorphic fungi usually gain access to human hosts?
Inhalation from the environment
What diseases are caused by Dermatophytes?
Superficial infections of keratinized tissues (skin, hair, nails, feathers)
What is the common name for tinea pedis?
Athlete’s foot
