Fungal Pathogens

Question 1

Explain the significance of fungal pathogens as opportunistic infections

Answer 1

.

Question 2

What is mycology?

Answer 2

study of fungi

Question 3

What is a yeast?

Answer 3

unicellular fungi

Question 4

What is hyphae?

Answer 4

multicellular filaments (mold)

Question 5

What are dimorphic fungi?

Answer 5

alternate between yeast and mold forms

Question 6

What is mycelium?

Answer 6

collection of hyphae (mushrooms)

Question 7

What is mycosis?

Answer 7

fungal infection

Question 8

What is mycosis?

Answer 8

fungal infection

Question 9

How does yeast reproduce?

Answer 9

budding, fission, sexual spores

Question 10

What is pseudohypha?

Answer 10

chain of yeast cells, there was no cytokinesis

Question 11

How does mold reproduce?

Answer 11

asexual spores, sexual spores

Question 12

Asexual spores

Answer 12

• sporangiospores wrapped in “sporangium”
• spread when sporangium bursts
• wind/water dispersed
• arthrospores - every other compartment turns into a spore

Question 13

Sexual spores

Answer 13

• zygospores (bread mold) (undergoes meiosis then mitosis)
• ascospores (baker’s yeast) (looks like a sac)
• basidiospores (mushrooms) (looks like a club)

Question 14

What is a zygospore?

Answer 14

fusion of 2 gametes of a zygomycete

Question 15

Types of Aspergillus spores (an Ascomycete)

Answer 15

• asexual reproduction: conidiospores

- may form sexual spores via meiosis (usually in fruiting body

Question 16

Describe and give examples of superficial mycoses

Answer 16

• spread via contact
  
  • skin: athlete’s foot, ringworms
  • mucous membranes: vaginal candidiasis

Question 17

Describe and give examples of subcutaneous mycoses

Answer 17

• spread through broken skin
  
  • mycetoma foot
  • sporotrichosis (from thorn or twig)

Question 18

Describe and give examples of system mycoces

Answer 18

• spread through inhalation
• mostly in immunocompromised
  
  • cryptococcal meningitis
  • pulmonary aspergillosis

Question 19

Why is system mycoces often overlooked?

Answer 19

insidious onset

primary diseases

Question 20

Describe dermatophytes

Answer 20

• prefer keratin

- asexual spores

Question 21

Candida albicans

Answer 21

• dimorphic fungi
• diaper rash, vaginal yeast infection
• can develop on medical devices/prosthetics

Question 22

Describe characteristics of systemic fungal infections spread via inhalation

Answer 22

• 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

Question 23

What illness does Cryptococcosis define and describe a few characteristics

Answer 23

• AIDS
• polysaccharide capsule and melanin
• neurotropic, spreads to CNS
• most common systemic myoces

Question 24

How does Cryptococcosis evade phagocytosis?

Answer 24

polysaccharide capsule

Question 25

Describe Histoplasmosis

Answer 25

Ohio Valley Disease - no capsule - asymptomatic lung infection - causes hepatosplenomegaly and hilar lymphadenopathy - mostly in east

Question 26

Describe Coccidioidomycosis

Answer 26

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

Question 27

Describe North American Blastomycosis

Answer 27

- Blastomyces dermatitis - large cells: thick wall, broad-based buds - infects lungs and skin

Question 28

Describe South American Blastomycosis

Answer 28

- Paracoccidioidomycosis | - multiple narrow-based buds from one cell

Question 29

Describe Aspergillus fumigatus

Answer 29

- most common cause of invasive aspergillosis - serious disease among immunocompromised - invasive hyphae in lung parenchyma and a blood vessel

Question 30

What is a-amanitin?

Answer 30

- inhibits eukaryotic RNA Polymerase II - liver failure (die within 24 hours) - from Amanita mushrooms (Death cap mushrooms)

Question 31

What are aflatoxins?

Answer 31

- produced by Aspergillus species - aflatoxin B1 causes liver cancer - growth impediment in children - liver damage = death

Question 32

What are ochratoxins?

Answer 32

- produced by A. orchraceous (grapes - contaminates wine), A. niger (black mold), & penicillin - carcinogenic and nephrotoxic