2E - Fungi

Question 1

Fungi affect on the body and protection from the body

Answer 1

◦ The cell walls and capsules of fungi are very foreign to the immune system of animals and fungal infection tend to cause an intense inflammatory response but the capsules and cell walls also protect the fungi from the immune response

Question 2

Fungal infectious agent relationship

Answer 2

commensal relationship with the host as microflora on mucus membranes
◦ Most of these agents exist either as branched filamentous forms (molds) or as yeasts
◦ Dimorphic fungi have both forms in their lifecycle

Question 3

Candida albicans causes

Answer 3

causes a disease called Candidasis (Thrush)

◦ Found in normal flora of GIT tract

Question 4

Candida albicans relationship with host

Answer 4

◦ The yeast phase has a commensal relationship with the host colonizing the mucous membranes with our causing disease

Question 5

how can candida albicans switch phases

Answer 5

◦ Changes in the physiology of the host may cause the yeast to switch to the filamentous, invasive phase
‣ Changes may include
• Changes in diet
• Increased stress levels
• Treatment with antibiotics and corticosteroids

Question 6

Aspergillosis cause

Answer 6

caused by a saprophytic fungal organism called Aspergillus fumigatus
◦ Picture notes : Aspergillosis in the lungs of an African Grey Parrot with psittacine beak and feather disease virus, a circovirus that, in juveniles, attacks the Bursa

Question 7

Aspergillosis disease process

Answer 7

◦ Animals encounter aspergillum app all the time and usually the innate immune system is very efficient at eliminating the organism
‣ Conidia, or spores, inhaled by animals are deposited on the mucosa of the nasopharynx and throughout the respiratory system
‣ But problems can occur in immunocompromised animals
• Nasal aspergillosis in dogs
• Mycotic abortion in cattle
• Immunocompromised humans → respiratory disease
◦ In very severe cases hyphae invade the blood vessels and then spread throughout the body
◦ The invading proliferating fungal hyphae may cause direct tissue damage
‣ However, much of the damage is caused by the intense inflammatory response (lots of chemical mediators and degradative enzymes) targeting the fungal hyphae

Question 8

Cryptococcosis neoformans pathogen type

Answer 8

aprophytic yeast that grows in warm, moist environments in certain soils

Question 9

Cryptococcosis neoformans yeast phase

Answer 9

yeast phase of Cryptococcosis causes the disease cryptococcosis
◦ The yeast phase of Cryptococcosis neoformans is resistant to the innate and adaptive immune response

Question 10

Pathogensis of cryptococcis

Answer 10

◦ Basidiospores of Cryptococcis neoformans are inhaled from the environment
◦ Normally the immune system can kill the basidiospores
◦ However in an immunocompromised individual the basidiospore quickly germinate into yeast cells that;
‣ Produce phospholipase, (enzyme), that degrades alveolar walls
‣ Produce a capsule that is anti-phagocytic and immunosuppressive
• That hides them from the macrophages and neutrophils
• Makes them resistant to phagocytosis
• Spreads directly from the nasal cavity to the brain
‣ Macrophages become distended with capsules forming cysts filled with gelatinous material observed grossly in the brain