Gross chapter 12 - (pyo)granulomatous

Question 1

Match Actinomyces and Nocardia with:

a) Gram-positive, nonacid-fast, filamentous, anaerobic or microaerophilic rods
b) Gram-positive, partially acid-fast, filamentous, aerobic rods

Answer 1

Actinomyces are Gram-positive, nonacid-fast, filamentous, anaerobic or microaerophilic rods

Nocardia are Gram-positive, partially acid-fast, filamentous, aerobic rods

Question 2

Is Actinomyces or Nocadia a commensal of the oral cavity and GIT in mammals?

Answer 2

Actinomyces

Question 3

What is another name for tissue grains - aggregates of bacteria imbedded in amorphous eosinophilic material that is presumed to consist of antigen–antibody complexes

Answer 3

Splendore-Hoeppli reaction

Question 4

Which modification of the acid-fast stain can help to differentiate Norcardia from Actinomyces?

Answer 4

Fite–Faraco modification (Fite’s stain)

This stain employs peanut oil to prevent excessive decolorisation of organisms during the staining process.

Question 5

How can you differentiate Norcadia from opportunistic mycobacterial infection?

Answer 5

Nocardia spp. accumulate in larger tangled colonies, are only partially or weakly acid-fast, and elicit a more prominent neutrophilic response

Question 6

What colour are tissue granules typically in a bacterial pseudomycetoma?

Answer 6

White

Question 7

What is the main differential diagnosis for bacterial pseudomycetoma?

Answer 7

Actinomyces

Question 8

How can you clinically differentiate feline leprosy from feline sporotrichosis?

Answer 8

The nodules of feline sporotrichosis have draining fistulous tracts (containing abundant organisms easily identified by direct smears) in contrast to the scantily exudative lesions of feline leprosy syndrome.

Question 9

Which form of feline leprosy is organism rich, lepromatous or tuberculoid?

Answer 9

Lepromatous

Question 10

Is a Grenz zone typically present in histopathology of feline leprosy?

Answer 10

Yes

Inflammation obscures normal dermal architecture, but often a thin zone of the superficial dermis is spared (Grenz zone).

Question 11

In which form of feline leprosy do you see large foci of necrosis surrounded by diffuse pyogranulomatous inflammation and occasional giant cells?

Answer 11

Tuberculoid

Question 12

Name two differentials for the lepromatous form of feline leprosy that also present with foamy macrophages

Answer 12

Cutaneous xanthoma
Opportunistic M. avium infection
Late lesions of feline progressive dendritic cell histiocytosis
Opportunistic fungal infection

Question 13

Can cases of canine leproid granuloma self resolve?

Answer 13

Yes, commonly in immunocompetent animals

Question 14

What is a predisposed site for canine leproid granuloma?

Answer 14

Dorsal surface of the pinnae
Head
Distal limbs

Question 15

Sterile granuloma and pyogranuloma syndrome produces multifocal lesions (less common in leproid granuloma) which tend to track along hair follicles, in contrast to the more diffuse pattern of leproid granuloma. True or false?

Answer 15

True

Question 16

Mycobacterium fortuitum, Mycobacterium smegmatis, and Mycobacterium chelonei-abscessus are the most frequently isolated facultative and opportunistic mycobacterial pathogens in dogs and cats. True or false?

Answer 16

True

Question 17

Runyon Group IV mycobacteria exhibit a marked tropism for tissues rich in lipids, leading to which site predilection in cats?

Answer 17

Inguinal fat pad (and disease predilection for obese individuals)

Question 18

Which characteristic clinical feature of feline opportunistic mycobacterial infection in cats is not observed in dogs?

Answer 18

The undermining of peripheral skin that is characteristic of feline opportunistic mycobacterial infection is not observed in dogs.

Question 19

Which stain is superior in labeling mycobacteria and may be of benefit in suspected cases with scant organisms? The stain may also detect partially degraded bacteria within macrophages.

Answer 19

The polyclonal anti-Mycobacterium bovis (BCG) stain

Question 20

Opportunistic mycobacteria may closely resemble Nocardia spp. in tissue but what is the typical difference between them?

Answer 20

Larger clusters or longer chains of bacteria characterise nocardiosis and these organisms are generally only partially acid-fast; however, culture may be required for ultimate differentiation.

Question 21

What is a histopathological difference between feline leprosy and feline M. avium complex infection? Both often have large numbers of organisms in foamy macrophages.

Answer 21

A fibrovascular network is present within the inflammatory infiltrate of Mycobacterium avium infection, in contrast to feline leprosy. Also, unlike the mycobacterium of feline leprosy, MAC organisms can be identified by culture.

Question 22

What histopathological and clinical feature can help distinguish M. canis dermatophytic pseudomycetoma from other fungal infections?

Answer 22

Most of the systemic and opportunistic fungi affecting cats and dogs are smaller and more uniform in appearance in tissue section, and do not accumulate in tissue grains or granules.

In contrast, the diffuse distribution of Trichophyton mentagrophytes in dermatophytic granulomas is similar to opportunistic fungal infection.

Question 23

Is cutaneous involvement more common in blastomycosis, histoplasmosis or coccidioidomycosis?

Answer 23

Skin lesions are seen in up to 40% of dogs with blastomycosis; they are uncommon in histoplasmosis and coccidioidomycosis

Question 24

Are fungal organisms most numerous in blastomycosis, histoplasmosis or coccidioidomycosis?

Answer 24

Histoplasmosis

Question 25

Rank in size order:
Blastomyces dermatitidis
Coccidiodes immitis
Histoplasma capsulatum

Answer 25

Histoplasma capsulatum 2-4um
Blastomyces dermatitidis 5-20um
Coccidiodes immitis 20-80um

Question 26

What do Blastomyces dermatitidis look like on histopathology and where are they found?

Answer 26

Spherical; 5–20um; double wall; broad based budding

Found free and in macrophages

Question 27

What do Coccidiodes immitis look like on histopathology and where are they found?

Answer 27

Spherules with endospores; 20–80um; double wall

Free

Question 28

What do Histoplasma capsulatum look like on histopathology and where are they found?

Answer 28

Egg-shaped; 2–4um; clear halo within single wall

Found in macrophages

Question 29

What is the most commonly diagnosed systemic mycosis in the cat?

Answer 29

Cryptococcosis

Question 30

Which body sites are most often affected by cutaneous cryptococcosis in cats?

Answer 30

Head, neck and ears

Firm subcutaneous swellings of the dorsal muzzle are a characteristic presentation

Question 31

What is a highly characteristic histopathological finding of cryptococcosis?

Answer 31

Abundant organisms surrounded by confluent unstained capsules create a pale, foamy or ‘soap bubble’ low-power appearance to the tissue that is highly characteristic of cryptococcosis.

Inflammation often is scant, but may be mild to moderate.

Question 32

Which stain will help identify the capsule of Cryptococcus neoformans on histopathology?

Answer 32

Mucicarmine

Question 33

How can you differentiate cryptococcosis from blastomycosis histopathologically?

Answer 33

Blastomyces dermatitidis lacks a capsule, has broad-based rather than narrow- based budding, and usually evokes more inflammation in tissue than does Cryptococcus neoformans.

Question 34

In cats with sporotrichosis, are high or low numbers of organisms present in draining fluid and tissue?

Answer 34

High numbers - substantial public health hazard

Question 35

What do the yeasts of Sporothrix schenckii look like?

Answer 35

Elongated, ‘cigar-shaped’ organisms (round in cross- section), 3 to 10 um in length and 1 to 2 um in diameter

Question 36

Do Alternaria and Cladosporium spp. cause phaeohyphomycosis or hyalohyphomycosis?

Answer 36

Phaeohyphomycosis (pigmented hyphal elements in tissue)

Question 37

What do fungal elements look like on histopathology with opportunistic fungal infections?

Answer 37

Many of the opportunistic fungi have branching, septate hyphae, sometimes with spore-like swellings. Morphology will vary depending on the species

Question 38

Which special stain should you use for suspected pythiosis and why?

Answer 38

Gomori’s methenamine silver (GMS) as it will stain the wall of living or dead fungi.

PAS is superior in detecting living organisms, and Pythium insidiosum often is devitalised in specimens obtained for histopathology.

Question 39

What do Prototheca look like on histopathology?

Answer 39

Round to oval, have thin highly refractile walls and a light to darkly basophilic internal structure, and measure 8 to 30mm in diameter.

Careful examination will reveal four to eight characteristic daughter cells, or endospores, that create a subdivided or ‘cut pie’ appear- ance to the organism.

Question 40

Which is most protective in leishmaniasis, antibody-mediated or cell-mediated immune response?

Answer 40

Cell-mediated

Antibody-mediated response can lead to organ damage from circulating immune complexes

Question 41

Which special stain can accentuate Leishmania amastigotes?

Answer 41

Giemsa

negative with PAS and GMS