Fungal Pathogens Flashcards
Explain the significance of fungal pathogens as opportunistic infections
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What is mycology?
study of fungi
What is a yeast?
unicellular fungi
What is hyphae?
multicellular filaments (mold)
What are dimorphic fungi?
alternate between yeast and mold forms
What is mycelium?
collection of hyphae (mushrooms)
What is mycosis?
fungal infection
What is mycosis?
fungal infection
How does yeast reproduce?
budding, fission, sexual spores
What is pseudohypha?
chain of yeast cells, there was no cytokinesis
How does mold reproduce?
asexual spores, sexual spores
Asexual spores
- sporangiospores wrapped in “sporangium”
- spread when sporangium bursts
- wind/water dispersed
- arthrospores - every other compartment turns into a spore
Sexual spores
- zygospores (bread mold) (undergoes meiosis then mitosis)
- ascospores (baker’s yeast) (looks like a sac)
- basidiospores (mushrooms) (looks like a club)
What is a zygospore?
fusion of 2 gametes of a zygomycete
Types of Aspergillus spores (an Ascomycete)
- asexual reproduction: conidiospores
- may form sexual spores via meiosis (usually in fruiting body
Describe and give examples of superficial mycoses
- spread via contact
- skin: athlete’s foot, ringworms
- mucous membranes: vaginal candidiasis
Describe and give examples of subcutaneous mycoses
- spread through broken skin
- mycetoma foot
- sporotrichosis (from thorn or twig)
Describe and give examples of system mycoces
- spread through inhalation
- mostly in immunocompromised
- cryptococcal meningitis
- pulmonary aspergillosis
Why is system mycoces often overlooked?
insidious onset
primary diseases
Describe dermatophytes
- prefer keratin
- asexual spores
Candida albicans
- dimorphic fungi
- diaper rash, vaginal yeast infection
- can develop on medical devices/prosthetics
Describe characteristics of systemic fungal infections spread via inhalation
- grow in soil, enhanced in bird/bat droppings
- geographically restricted
- thermal dimorphism: hyphae at environmental temps
- mild symproms in healthy people; disseminate to skin and other organs in immunocompromised
- chronic, hard to diagnose
- Cryptococcus neoformans, Histoplasma capsulatum, Coccidioides immitis, Blastomyces dermatidis, Paracoccidioides brasiliensis
What illness does Cryptococcosis define and describe a few characteristics
- AIDS
- polysaccharide capsule and melanin
- neurotropic, spreads to CNS
- most common systemic myoces
How does Cryptococcosis evade phagocytosis?
polysaccharide capsule
Describe Histoplasmosis
Ohio Valley Disease
- no capsule
- asymptomatic lung infection
- causes hepatosplenomegaly and hilar lymphadenopathy
- mostly in east
Describe Coccidioidomycosis
Valley Fever
- no true yeast form – 2 agents: C. immitis, C. posadasii
- mainly in southwest US due to alkaline soil and semiarid climate
- high risk for lab infections
- disseminate to skin and meninges
- large sperule with endospores
Describe North American Blastomycosis
- Blastomyces dermatitis
- large cells: thick wall, broad-based buds
- infects lungs and skin
Describe South American Blastomycosis
- Paracoccidioidomycosis
- multiple narrow-based buds from one cell
Describe Aspergillus fumigatus
- most common cause of invasive aspergillosis
- serious disease among immunocompromised
- invasive hyphae in lung parenchyma and a blood vessel
What is a-amanitin?
- inhibits eukaryotic RNA Polymerase II
- liver failure (die within 24 hours)
- from Amanita mushrooms (Death cap mushrooms)
What are aflatoxins?
- produced by Aspergillus species
- aflatoxin B1 causes liver cancer
- growth impediment in children
- liver damage = death
What are ochratoxins?
- produced by A. orchraceous (grapes - contaminates wine), A. niger (black mold), & penicillin
- carcinogenic and nephrotoxic
