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Veterinary Bacteriology & Mycology > Systemic Mycoses > Flashcards

Systemic Mycoses Flashcards

1
Q

What 4 genera typically cause systemic mycoses?

A
  1. Coccidioides - inanimate mold, sporangia in tissue
  2. Histoplasma - inanimate mold, budding yeast in tissue
  3. Blastomyces - inanimate mold, budding yeast in tissue
  4. Aspergillus - budding yeast in tissue
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2
Q

How is systemic mycoses transmitted? When is infection primarily seen? Is it contagious?

A

inhalation

in immunocompromised animals

NO

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3
Q

How do systemic mycoses lesions tend to appear?

A

granulomatous to pyogranulomatous (lung) with dissemination to bone, skin, CNS, or abdominal visera

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4
Q

What 2 species cause coccidioidomycosis? What are the main hosts and habitat? Site of lesion?

A
  1. Coccidioides immitis
  2. Coccidioides posadasii

dogs, cats, horses, humans
soil of low elevation deserts

primary lesions in lungs with secondary lesions in bones

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5
Q

What are the 6 major virulence factors of Coccidioides?

A
  1. adhesins (SOWgp): affinity for extracellular matrix proteins (laminin, fibronectin, collagen)
  2. β-glucosidase 2: secreted by endospores that play a role in morphology
  3. chitinase 2 - formation and release of endospored from spherule
  4. β-1.3-glucanosyltransferase: surface endospore
  5. serine proteases - stimulation of inflammatory response by digesting elastin, collagen, and Ig
  6. urease
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6
Q

What parts of Coccidoides have antiibodies made against in early and late infection? What 2 virulence factors elicit Th1 responses?

A
  • EARLY = β-glucosidase (IgM)
  • LATE = chitinase 1 (IgG), diagnostically useful and detected by complement fixation
  1. β-1,3-glucanosyltransferase - results in elevated IFN-γ production and protection against disseminated disease
  2. urease - protective immunity, activates macrophages
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7
Q

How does Coccidioides grow on media?

A

SDA or blood - mycelial
- dull colonies gradually develop sparse aerial mycelium
- arthroconidia produced within 5-7 days

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8
Q

What is the pathogenesis of Coccidioides?

A
  • hyphae fragment into arthroconidia, which are inhaled and form spherules in tissues
  • spherules rupture and release endospores, which form more spherules
  • dissemination from lung to a variety of other tissue is possible, especially CNS, local LN, bone, skin, pericardium, and eyes
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9
Q

Coccidioidomycosis, dog:

A
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10
Q

Coccidioidomycosis, dissemination:

A
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11
Q

What are 4 ways that Coccidioidomycosis is diagnosed?

A
  1. skin test - coccidioidin
  2. immunodiffusion - multiple bands = active infection; single band = chronic infection
  3. complement fixation - Ab titers rise in disseminated disease
  4. latex agglutination test - IgM in early disease
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12
Q

What are the 4 recommended treatments for Coccidioidomycosis?

A
  1. fluconazole*
  2. ketoconazole*
  3. itraconazole*
  4. amphotericin B
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13
Q

What causes Histoplasmosis? What 2 phases does it take? What 3 varieties are there?

A

Histoplasma capsulatum

  1. MOLD = 25-30 degrees C, saprophytic
  2. YEAST = 37 degrees C, parasitic)

vars. capsulatum, duboisii, farciminosum
- histoplasmosis is discussed without regard for varietal distinction

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14
Q

What is the free-living form of Histoplasma capsulatum?

A

septate hyphae bearing….
- spherical to pyriform microconidia
- tuberculate macroconidia, thick-walled spheroidal cells studded with finger-like projections

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15
Q

What are used for immunodiagnosis of Histoplasmosis?

A

histoplasmins

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16
Q

What are the 4 major virulence factors of Histoplsma capsulatum?

A
  1. adhesins - bind to β-2 integrins on the surface of neutrophils, macrophages, and DC, allowing it to enter without triggering an effective oxidative burst
  2. calcium-binding protein - chelates available calcium within the phagolysosome, impeding the effectiveness of calcium-requiring lysosomal enzymes
  3. iron acquisition - removes iron from host iron-binding proteins transferring and lactoferrin
  4. melanin - reduces the toxicity of hydroxyl radicals, superoxides, and singlet oxygen radicals in the phagolysosome
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17
Q

What are the H and M antigens of Histoplasma capsulatum?

A

H = β-glucosidase that elicits a cell-mediated immunoresponse to the yeast (parasitic) phase

M = catalase that plays a role in the survival of the yeast phase in the phagolysosome

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18
Q

How does Histoplasma capsulatum survive in the phagolysosome?

A

it acidifies the environment within the phagolysosome from a pH of <5 to 6-6.5, which reduces the activity of the lysosomal enzymes

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19
Q

What are the 6 classes of Histoplasma capsulatum?

A
  • 1 and 2 = North America
  • 3 = Central and South America
  • 4 = Florida
  • 5 and 6 = human patients with acquires immunodeficiency syndrome from NY and Panama
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20
Q

Where is Histoplasma capsulatum found in the environment? How is it transmitted?

A

topsoil layers, especially in the presence of bird (starlings, chickens) and bat guano

inhalation of microconida or hyphal fragments
- ingestion, wound infection

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21
Q

Where are the lesion sites of Histoplasmosis?

A

primarily in lungs with dissemination to intestines and other organs

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22
Q

How does the form of Histoplasmosis compare in the environment and within the host?

A

ENVIRONMENT = mold with aerial hyphae

HOST = oval, budding yeast that can be phagocytized by immune cells and transported to regional LN and disseminate

23
Q

Histoplasmosis, cat:

A
24
Q

Histoplasmosis, bone dissemination:

A
  • soft tissue swelling
  • osteolysis of carpal bones
  • collapsed joint spaces
  • distal radius has punctate osteolysis
  • periosteal reaction in proximal metacarpal
25
Q

Histoplasmosis:

A
26
Q

In what 4 ways is Histoplasmosis diagnosed? What 4 treatments are recommended?

A
  1. skin test - Histoplasmin, positive reaction means only exposure
  2. immunodiffusion
  3. complement fixation, latex agglutination - humans
  4. immunofluorescence - yeast cells in exudates and tissue

ketoconazole, itraconazole, fluconazole, amphotericin B

27
Q

What causes blastomycosis? What 2 forms does it take?

A

Blastomyces dermatitidis

  1. MOLD in soil (saprophytic)
  2. YEAST in tissue (parasitic)
28
Q

What spores does Blastomyces dermatitidis produce? How does it grow on blood agar?

A

conidiophores with spherical or oval smooth-walled conidia

at 37 degrees C - thick-walled yeast that reproduces by single buds attached to a broad base

29
Q

What is the major virulence factor of Blastomyces? What 2 functions does it have?

A

adhesin (Bad1)

  1. binds to phagocytic cells resulting in little generation of ROS and nitrogen intermediates
  2. downregulates the production of proinflammatory cytokines
30
Q

What are the main hosts of Blastomyces? What is their usual habitat? Where are lesions most common?

A

dogs, cats, humans

acidic soil rich in organic material

primary lesions in lungs with dissemination to skin and other organs

31
Q

What are the 6 steps to blastomycosis pathogenesis?

A
  1. spore inhalation
  2. deposit in alveoli
  3. acute pulomary phase resulting in self-limiting control of asexual reproduction or…..
  4. asexual budding not eliminated by the immune system (or due to immunocompromisation)
  5. pyogranulomatous inflammation within the lungs
  6. lymphatic and hematogenous spread of spores causes inflammation in skin, bones, eyes, CNS, and/or reproductive tract
32
Q

Blastomycosis:

A
33
Q

What is a common presentation when blastomycosis affects the eyes?

A

subretinal granuloma and serous retinal detachment
- with treatment, retinal detachment should flatten and granuloma should reduce in size

34
Q

Blastomycosis, cat cutaneous lesions:

A
35
Q

In what 4 ways is blastomycosis diagnosed? What is the recommended treatment?

A
  1. culture on SDA and direct examination of intracellular yeast
  2. skin test - lacks sensitivity and specificity
  3. immunodiffusion, complement fixation, ELISA, counter-immunoelectrophoresis
  4. immunofluorescence - yeast cells in exudates and tissue

itraconazole**, amphotericin B, ketoconazole

36
Q

What is the most frequent Aspergillus causing animal and human infection? What kind of fungi are they?

A

Aspergillus fumigatus

molds consisting of septate hyphae and characteristic asexual fruiting structures borne on conidiophores

37
Q

What is the characteristic structure found on Aspergillus spp.?

A

conidiophores - hyphal branches originating by a foot cell in the vegetative mycelium and ending in an expanded vesicle covered by layers of flask-shaped phialides from which chains of pigmented conidia grow

38
Q

What are the 5 major virulence factors of Aspergillus spp.?

A
  1. adhesins - bind to extracellular matrix proteins (collagen, fibronectin, fibrinogen, laminin)
  2. cell wall - PAMP recognized by Toll-like receptors on the surface of host macrophages, resulting in the secretion of proinflammatory cytokines
  3. extracellular enzymes - breaks down host tisue, including elastase, protease, phospholipase
  4. iron acquisition
  5. melanin pigment - free radical scavenger
39
Q

Where are Aspergilli found in the environment? How is Aspergillosis acquired?

A

soil, vegetation, feed, air, water

environmental - inhalation or ingestion

40
Q

What are the 5 steps to Aspergillosis pathogenesis?

A
  1. infection acquired from environmental sources - inhalation/ingestion
  2. opportunistic pathogen that can impair, overwhelm, or bypass host defense to permit hyphal invasion of tissues
  3. pulmonary infection with suppurative exudates in the bronchioles
  4. mycelial growth may extend into blood vessels, leading to vasculitis, thrombus formation, and dissemination
  5. granulomas can develop in many body organs and are visible as yellowish-grey nodules
41
Q

What are the most common diseases caused by Aspergillus spp. in cattle, horses, dogs, and birds?

A

CATTLE: abortion, mastitis, intestinal aspergillosis, pneumonia

HORSES: guttural pouch mycosis*, nasal granuloma, keratomycosis, intestinal aspergillosis

DOGS: nasal aspergillosis, otitis externa, systemic aspergillosis

BIRDS: brooder pneumonia, aspergillosis (pneumonia and air sacculitis)

42
Q

Aspergillosis, placentitis:

A
  • cattle
  • thickened, leathery
  • mycotic abortion
43
Q

Aspergillosis, abortion:

A

fungal plaques

44
Q

How are horses most commonly affected with Aspergillosis? How does it commonly present?

A

guttural pouch mycosis

  • nasal discharge, usually unilateral
  • swelling of Viborg’s triangle
  • cranial nerve and vessel involvement results in epistaxis, unilateral facial paralysis, and dysphagia
45
Q

What are the 3 major presentations of Aspergillosis in poultry?

A
  1. brooder pneumonia - newly hatched chicks inhale aerosols
  2. pneumonia and air sacculitis - sporadic in young birds
  3. generalized aspergillosis - stress in captive birds
46
Q

What is the mos common presentation of Aspergillosis in dogs? How does it present?

A

nasal aspergillosis in young urban dogs

  • chronic nasal discharge, often unilateral
  • sneezing
  • epistaxis
  • damage to nasal mucosa and turbinates
  • otitis externa
47
Q

Aspergillosis, cat:

A
48
Q

What is bovine abortion caused by Aspergillus spp. commonly related to? Aspergillosis in chickens?

A

moldy fodder, poor weather and housing

heavily contaminated litter, poor husbandry

49
Q

In which dogs are Aspergillosis most common? What practice makes horses more susceptible to Aspergillus keratomycosis?

A

young dolichocephalic breeds

frequent use of topical antibacterials and steroids that cause immunosuppression and impaired colonization resistance

50
Q

What is the major factor that limits Aspergillus dissemination?

A

cell-mediated immunity
- immunization procedures not available

51
Q

How is Aspergillosis diagnosed? How is the nasal form in dogs treated? Disseminated form?

A
  • direct examination - hyphae, fruiting heads, conidia
  • culture
  • immunodiffusion
  • ELISA, PCR

topical instillation of clotrimazole or enilconazole into the nasal passage and sinuses (itraconazole can be given orally)

itraconazole

52
Q

What does Pneumocystis carinii cause?

A

severe pneumonia in immunocompromised (opportunistic!)
- especially horses and dogs

53
Q

What are the 4 most common diseases caused by Rhisopus spp., Rhizomucor spp., Absidia spp., Mucor spp., and Mortierella spp.? What animals are most affected?

A
  1. mycotic bovine abortion
  2. GI infection marked ulcerative lesions and mesenteric lymphadenitis
  3. respiratory infection
  4. hematogenous infection affecting viscera and CNS

ruminants, swine, dogs

Veterinary Bacteriology & Mycology (47 decks)

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