5. Medical Mycology Flashcards
Lecture 5
Define mycoses
- 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)
Why are plants more susceptible to disease from fungal infection than animals?
Animals
•immune system is effective
• grow slowly under low oxygen
• few are capable of growth at 37˚C
Plants
• abundant oxygen
Human fungal diseases characteristics
- ubiquitous yet rarely life threatening
- skin, hair, nail diseases estimated most common human disease
- mucosal surface infections - thrush
Define dermatophyte
A pathogenic fungus that grows on skin, mucous membranes, hair, nails, feathers, and other body surfaces, causing ringworm and related diseases.
Superficial infections
dermatophytes
Subcutaneous infections
- 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
Whose life is most in danger by human fungal diseases
Immunocompromised people or complications from other diseases
Microsporidia
- phylum - microspora
- minute, obligate intracellular parasites
- lack normal mitochondria and no flagella
- spore wall is made of chitin and stains with calcofluor white
Microsporidia life cycle
- 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
What are obligate pathogens?
- bacteria that must infect a hose in order to survive
* in contrast, some bacteria can survive outside of a host
Pneumocystis
- obligate pathogens
- pulmonary disease
- may be one species per mammalian species
Candida albicans and other candida spp
- 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
What is one virulence property of candida albicans?
Ability to switch between yeast and hyphal growth
Dimorphic define (candida spp)
Transition between yeast and hyphal forms of growth
When do symptoms develop for C. albicans?
- if bacterial competitors disrupted
- during pregnancy - elevated progesterone
- stress
When can C. albicans become invasive?
- in HIV
- leukemia
- diabetes
- corticosteroid
- transplant patients
What are the three locations of disease caused by candida albicans?
- superficial
- subcutaneous
- systemic
Infection pathway of cryptococcus spp
- bird excretion on tree and spores are releases
- spores are inhaled into the lungs
- lodge in the alveoli
- dissemination to central nervous system
Aspergillus fumigatus
- high spore production
* resists high temperature
Two types of aspergillus fumigatus infections
Systemic aspergillosis
• organ transplant patient, suppressed immune system - fungus grows in tissue
Farmer’s lung
• inhalation of large numbers of spores
• induces allergic reaction
Why are few fungicides available in medicine?
- 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
What is ergotism
poisoning produced by eating food affected by ergot, typically resulting in headache, vomiting, diarrhoea, and gangrene of the fingers and toes.
What is a mycotoxin
any toxic substance produced by a fungus.