5. Medical Mycology

Question 1

Define mycoses

Answer 1

• Mycoses are common
• a variety of environmental and physiological conditions can contribute to the development of fungal diseases.

mycosis - fungal infection of animals (including humans)

Question 2

Why are plants more susceptible to disease from fungal infection than animals?

Answer 2

Animals
•immune system is effective
• grow slowly under low oxygen
• few are capable of growth at 37˚C

Plants
• abundant oxygen

Question 3

Human fungal diseases characteristics

Answer 3

• ubiquitous yet rarely life threatening
• skin, hair, nail diseases estimated most common human disease
• mucosal surface infections - thrush

Question 4

Define dermatophyte

Answer 4

A pathogenic fungus that grows on skin, mucous membranes, hair, nails, feathers, and other body surfaces, causing ringworm and related diseases.

Question 5

Superficial infections

Answer 5

dermatophytes

Question 6

Subcutaneous infections

Answer 6

• usually from wounding esp. tropical parts of the world
• can spread through lymph system

•candida species are sometimes classified in this group if they breach mucosal surfaces

Question 7

Whose life is most in danger by human fungal diseases

Answer 7

Immunocompromised people or complications from other diseases

Question 8

Microsporidia

Answer 8

• phylum - microspora
• minute, obligate intracellular parasites
• lack normal mitochondria and no flagella
• spore wall is made of chitin and stains with calcofluor white

Question 9

Microsporidia life cycle

Answer 9

• spores ingested from environment
• invade host cell by everting structure known as polar tube
• sporoplasm (parastie cell without wall) is injected through the tube into the host cell

Question 10

What are obligate pathogens?

Answer 10

• bacteria that must infect a hose in order to survive

* in contrast, some bacteria can survive outside of a host

Question 11

Pneumocystis

Answer 11

• obligate pathogens
• pulmonary disease
• may be one species per mammalian species

Question 12

Candida albicans and other candida spp

Answer 12

• C. albicans is a normal part of most people’s microflora
• ~50% incidence in human population
• causes thrush, vaginitis and in rare cases systemic disease

Question 13

What is one virulence property of candida albicans?

Answer 13

Ability to switch between yeast and hyphal growth

Question 14

Dimorphic define (candida spp)

Answer 14

Transition between yeast and hyphal forms of growth

Question 15

When do symptoms develop for C. albicans?

Answer 15

• if bacterial competitors disrupted
• during pregnancy - elevated progesterone
• stress

Question 16

When can C. albicans become invasive?

Answer 16

• in HIV
• leukemia
• diabetes
• corticosteroid
• transplant patients

Question 17

What are the three locations of disease caused by candida albicans?

Answer 17

• superficial
• subcutaneous
• systemic

Question 18

Infection pathway of cryptococcus spp

Answer 18

• bird excretion on tree and spores are releases
• spores are inhaled into the lungs
• lodge in the alveoli
• dissemination to central nervous system

Question 19

Aspergillus fumigatus

Answer 19

• high spore production

* resists high temperature

Question 20

Two types of aspergillus fumigatus infections

Answer 20

Systemic aspergillosis
• organ transplant patient, suppressed immune system - fungus grows in tissue

Farmer’s lung
• inhalation of large numbers of spores
• induces allergic reaction

Question 21

Why are few fungicides available in medicine?

Answer 21

• difficult to treat
• many antifungals have severe side effects
• treatment approach depends upon species of fungus and the site of the disease
• emergence of drug resistant strains

Question 22

What is ergotism

Answer 22

poisoning produced by eating food affected by ergot, typically resulting in headache, vomiting, diarrhoea, and gangrene of the fingers and toes.

Question 23

What is a mycotoxin

Answer 23

any toxic substance produced by a fungus.