Yeast

Question 1

How do molds and yeasts compare?

Answer 1

MOLDS = hyphae —> fuzzy, wooly

YEAST = single cell, budding —> “bacteria-like”

Question 2

What 3 yeasts are of highest importance in veterinary medicine?

Answer 2

1. Crytococcus neoformans
2. Malassezia pachydermatis
3. Candida albicans

Question 3

What lesions is Cryptococcus neoformans associated with? What 3 places are especially affected?

Answer 3

ulcerative lesions affecting mucous membranes

1. respiratory tract + nasal sinuses
2. CNS, meninges
3. eyes, chorioretinitis

Question 4

How does Cryptococcus neoformans infection compare in cats, cows, and horses? What other animals can be affected?

Answer 4

• CATS: more severly affected —> systemic mycosis
• COWS: mastitis
• HORSES: endometritis, abortion

dogs, ferrets, sheep, goats, llamas, parrots, elk, immunocompromised humans (opportunistic)

Question 5

What are the 2 major structural characteristics of Cryptococcus neoformans?

Answer 5

1. spherical cells
2. monomorphic

Question 6

What 4 aspects of Cryptococcus neoformans are associated with its pathogenesis?

Answer 6

1. contains sialic acid - direct complement proteins to degradation
2. produces phospholipase - membrane destruction of host cells
3. produces melanin - powerful antioxident, resists enzyme degradation and radiation, allows nutrient absorption
4. thick capsule - prevents antibody phagocytosis, stimulates T regulatory cells, inactivates alternative complement pathway

Question 7

What are 4 growth characteristics of Crytococcus neoformans?

Answer 7

1. grows at room temperature to 37 degrees C
2. encapsulation is optimal in chocolate agar plates with 5% CO2
3. produces melanin-pigmented colonies
4. four antigenic types: A, B, C, D

Question 8

In what 2 places in the environment does Cryptococcus neoformans prefer?

Answer 8

1. surface dust and dirt
2. dried pigeon feces for up to 1 year (rich in creatinine)

Question 9

How is Cryptococcus neoformans transmitted?

Answer 9

respiratory
- rarely percutaneous
- non-contagious

Question 10

What 3 pathologies are most commonly seen in Cryptococcus neoformans infection?

Answer 10

• CNS: meningitis, encephalitis, granuloma formation
• PULMONARY: bilateral miliary lesions, lobar pneumonia
• CUTANEOUS: traumatic implantation, ulcerative papules, nodules, granulomas, ulcers, manifestation of systemic disease

Question 11

Cryptococcus neoformans, cat:

Answer 11

species most severely affected

Question 12

What 2 immunological reactions can be used to diagnose Cryptococcus neoformans infection?

Answer 12

1. serological detection of capsule antibodies
2. cell-mediated immunity - macrophage and NK cell activation

Question 13

In what 3 ways can the laboratory diagnose Cryptococcus neoformans infection?

Answer 13

1. direct examination with India ink from exudates, tracheobronchial washes, and CSF
2. histopathology with Wright and Giemsa staining
3. culture, blood agar, SDA at room temperature of 30 degrees C

Question 14

What are the 3 recommended treatments for Cryptococcus neoformans infection? How is infection controlled?

Answer 14

1. fluconazole
2. itraconazole
3. 5-fluorocytosine

disinfect surfaces and facilities

Question 15

What are the 2 structural charactertics of Malassezia pachydermatis? How does it typically grow on media?

Answer 15

1. oval budding yeast
2. filaments not usually observed

cultured on blood agar with greenish tint seen on the surface at 25-41 degrees C
- aerophilic, microaerophilic

Question 16

What 4 enzymes are produced by Malassezia pachydermatis? What genetic phenotypes foes it have?

Answer 16

1. proteinase
2. chondroitin sulfatase
3. hyaluronidase
4. phopholipase

A, B, C, D

Question 17

Where is Malassezia pachydermatis commonly found? What diseases is it commonly associated with?

Answer 17

skin and ear canals of dogs, cats, ferrets, ruminants, and horses (opportunistic)

otitis externa and dermatitis

Question 18

What 6 dog breeds are most susceptible to Malassezia pachydermatis infection?

Answer 18

1. Australian silky terriers
2. basset hounds
3. cocker spaniels
4. dachshunds
5. poodles
6. West Highland white terriers

Question 19

How does Malassezia pachydermatis characteristically look under direct examination?

Answer 19

roll cotton swabs over glass slides and stain with Wright and Giemsa —> pink bottle-shaped or “shoe print”

Question 20

What 5 treatments are recommended for Malassezia pachydermatis infection?

Answer 20

1. nystatin
2. clotrimazole
3. miconazole
4. ketoconazole
5. itraconazole

Question 21

Malassezia pachydermatis, ear infection:

Answer 21

Question 22

What is Malassezia pachydermatis dermatitis assoicated with?

Answer 22

allergic dermatitis

Question 23

Where is Candida albicans commonly found? What animals are most susceptible to Candidiasis?

Answer 23

normal flora of mucous membranes of most mammals and birds

• immunocompromised
• overuse of antibiotics, steroids, hormones

Question 24

What is the structure of Candida albicans like? What 2 structures does it typically take upon spore formation?

Answer 24

oval budding yeast cells that sprout germ tubes that develop into septate-branching epithelium

1. blastoconidia
2. chlamydospore - thick-walled sphere attached to mycelium, in vitro only

Question 25

Candida albicans, structure:

Answer 25

Question 26

What 2 cellular products does Candida albicans produce?

Answer 26

1. adhesin: adheres to extracellular matric proteins 2. protease/neuraminidase: promotes tissue invasion and adherence to host cells

Question 27

What are the growth characteristics of Candida albicans? Where is it typically found?

Answer 27

aerobic, 25-30 degrees C, SDA mucocutaneous areas, and GI and genital tracts of mammals and birds

Question 28

How is Candida albicans transmitted

Answer 28

endogenous infection since it is commensal, which can result in hematogenous spread leading to systemic infection

Question 29

What 3 parts of Candida albincans structure contribute to its pathogenesis? How does infection present?

Answer 29

1. adhesin 2. cell wall glycoproteins - endotoxins 3. proteases/phospholipases - virulence affects mucous surfaces of GI tract from mouth to stomach, leaving whitish, yellow, or gray plaques with areas of ulceration and inflammation - also: genital tract, skin, claws

Question 30

What happens upon septicemic Candida albicans infection?

Answer 30

spreads to respiratory and intestinal tracts

Question 31

How does Candida albicans infection compare in birds, swine, horses, cattle, and cats/dogs?

Answer 31

- BIRDS = GI tract - SWINE = GI tract - HORSES = GI tract - CATTLE = pneumonia, enteritis, mastitis, systemic candidiasis - CATS/DOGS: non-healing ulcerative lesions on the oral, upper respiratory, GI, and genitourinary mucosa

Question 32

How does the laboratory diagnose Candida albicans infection? What 4 stains are used?

Answer 32

presence of blastoconidia or pseudohyphae 1. Gram 2. Wright-Giemsa 3. periodic acid Schifft 4. Gomori metheneamine silver

Question 33

How are birds, mammals, and dogs/cats treated for Candida albicans infection?

Answer 33

BIRDS: copper sulfate in water, nystatin MAMMALS: amphotericin B, itraconazole, miconazole DOGS/CATS: fluconazole, flucytosine