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Veterinary Bacteriology & Mycology > Yeast > Flashcards

Yeast Flashcards

1
Q

How do molds and yeasts compare?

A

MOLDS = hyphae —> fuzzy, wooly

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

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2
Q

What 3 yeasts are of highest importance in veterinary medicine?

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

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

A

ulcerative lesions affecting mucous membranes

  1. respiratory tract + nasal sinuses
  2. CNS, meninges
  3. eyes, chorioretinitis
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4
Q

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

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

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

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5
Q

What are the 2 major structural characteristics of Cryptococcus neoformans?

A
  1. spherical cells
  2. monomorphic
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6
Q

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

A
  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
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7
Q

What are 4 growth characteristics of Crytococcus neoformans?

A
  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
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8
Q

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

A
  1. surface dust and dirt
  2. dried pigeon feces for up to 1 year (rich in creatinine)
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9
Q

How is Cryptococcus neoformans transmitted?

A

respiratory
- rarely percutaneous
- non-contagious

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10
Q

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

A
  • CNS: meningitis, encephalitis, granuloma formation
  • PULMONARY: bilateral miliary lesions, lobar pneumonia
  • CUTANEOUS: traumatic implantation, ulcerative papules, nodules, granulomas, ulcers, manifestation of systemic disease
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11
Q

Cryptococcus neoformans, cat:

A

species most severely affected

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12
Q

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

A
  1. serological detection of capsule antibodies
  2. cell-mediated immunity - macrophage and NK cell activation
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13
Q

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

A
  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
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14
Q

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

A
  1. fluconazole
  2. itraconazole
  3. 5-fluorocytosine

disinfect surfaces and facilities

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15
Q

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

A
  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

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16
Q

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

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

A, B, C, D

17
Q

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

A

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

otitis externa and dermatitis

18
Q

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

A
  1. Australian silky terriers
  2. basset hounds
  3. cocker spaniels
  4. dachshunds
  5. poodles
  6. West Highland white terriers
19
Q

How does Malassezia pachydermatis characteristically look under direct examination?

A

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

20
Q

What 5 treatments are recommended for Malassezia pachydermatis infection?

A
  1. nystatin
  2. clotrimazole
  3. miconazole
  4. ketoconazole
  5. itraconazole
21
Q

Malassezia pachydermatis, ear infection:

A
22
Q

What is Malassezia pachydermatis dermatitis assoicated with?

A

allergic dermatitis

23
Q

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

A

normal flora of mucous membranes of most mammals and birds

  • immunocompromised
  • overuse of antibiotics, steroids, hormones
24
Q

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

A

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
25
Q

Candida albicans, structure:

A
26
Q

What 2 cellular products does Candida albicans produce?

A
  1. adhesin: adheres to extracellular matric proteins
  2. protease/neuraminidase: promotes tissue invasion and adherence to host cells
27
Q

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

A

aerobic, 25-30 degrees C, SDA

mucocutaneous areas, and GI and genital tracts of mammals and birds

28
Q

How is Candida albicans transmitted

A

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

29
Q

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

A
  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

30
Q

What happens upon septicemic Candida albicans infection?

A

spreads to respiratory and intestinal tracts

31
Q

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

A
  • 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
32
Q

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

A

presence of blastoconidia or pseudohyphae

  1. Gram
  2. Wright-Giemsa
  3. periodic acid Schifft
  4. Gomori metheneamine silver
33
Q

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

A

BIRDS: copper sulfate in water, nystatin

MAMMALS: amphotericin B, itraconazole, miconazole

DOGS/CATS: fluconazole, flucytosine

Veterinary Bacteriology & Mycology (47 decks)

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