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Infectious Agents > Exam 2: Dermatophilus, Nocardia, and Actinomyces > Flashcards

Exam 2: Dermatophilus, Nocardia, and Actinomyces Flashcards

1
Q

What is Dermatophilus congolensis commonly called in cattle, goats, and horses?

A

Cutaneous streptothrichosis

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2
Q

What is Dermatophilus congolensis termed in sheep when the wooled areas of the body are affected?

A

Lumpy wool

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3
Q

What are 2 morphologic forms of Dermatophilus congolensis?

A

Filamentous hyphae and motile zoospores

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4
Q

What factors allow Dermatophilus congolensis to thrive?

A

Prolonged wetting by rain
High humidity
High temperature
Various ectoparasites

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5
Q

When do epidemics with Dermatophilus congolensis occur?

A

During the rainy season

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6
Q

What can spread an infection of Dermatophilus congolensis?

A

Shearing, dipping, introducing an infected animal into a herd or flock

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7
Q

What do zoospores of Dermatophilus congolensis do?

A

Germinate to produce hyphae, which penetrate into the living epidermis

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8
Q

What happens to the epithelium invaded by Dermatophilus congolensis?

A

It cornices and separates in the form of a scab

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9
Q

What do wet scabs do with Dermatophilus congolensis?

A

Enhances the proliferation and release of zoospores from hyphae

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10
Q

What is Dermatophilus congolensis most prevalent in?

A

The young animals chronically exposed to moisture and immunosuppressed hosts

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11
Q

What speeds the healing of infection from Dermatophilus congolensis?

A

Onset of dry weather

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12
Q

What are the primary economic consequences of Dermatophilus congolensis?

A

Damaged hides in cattle
Wool loss in sheep
Lameness and loss of performance in horses when severely affected around the pastern area

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13
Q

What are the 3 stages that lesions from Dermatophilus congolensis can be observed in cattle?

A

Hairs matted together as paint-brush lesions
Crust or scab formation as the initial lesions coalesce
Accumulations of cutaneous keratinized material forming wart-like lesions that are 0.5-2 cm

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14
Q

What do typical lesions from Dermatophilus congolensis consist of?

A

Raised, matted gifts of hair

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15
Q

What are chronic lumpy wool infections from Dermatophilus congolensis characterized by?

A

Pyramid-shaped masses of scab material bound to wool fibers

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16
Q

What are lesions from Dermatophilus congolensis on horses like?

A

Matted hair and paint-brush lesions leading to crust or scab formation with yellow-green pus present under larger scabs

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17
Q

What does histopathalogic exam of Dermatophilus congolensis reveal?

A

The characteristic branching hyphae with multidimensional spetations, coccoid cells, and zoospores in the epidermis

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18
Q

What are Dermatophilus congolensis organisms like in active lesions? Chronic lesions?

A

Usually abundant in active lesions

Sparse or absent in chronic lesions

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19
Q

What does the diagnosis of Dermatophilus congolensis depend on?

A

The appearance of lesions in clinically diseased animals and demonstration of Dermatophilus congolensis in stained smears or histologic sections from scaps

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20
Q

What is the most practical diagnostic test for Dermatophilus congolensis?

A

Cytologic examination of fresh crusts and/or impression smears of the underside of freshly avulsed lesions

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21
Q

How can Dermatophilus congolensis been seen?

A

Under oil immersion as 2-6 parallel rows of gram-positive cocci that look like railroad tracks

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22
Q

What antimicrobials is Dermatophilus congolensis susceptible to?

A 
Erythromycin
Spiramycin
Penicillin G
Ampicillin
Chloramphenicol
Streptomycin
Amoxivillin
Tetracyclines
Novobiocin
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23
Q

How can chronic infections of Dermatophilus congolensis be cured?

A

With a single IM injection of procaine penicillin (22,000 IU/kg) and streptomycin (22 mg/kg)

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24
Q

How should lesions from Dermatophilus congolensis in horses be treated?

A

Theshould be gently soaked and removed

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25
Q

What is nocardia?

A

Gram-positive, strictly aerobic, nonmotile, pleomorphic, and nonsporeforming
Organisms in this genus mat take the form of rods, cocci, or diphtheroids, and they sometimes produce branching filaments and aerial hyphae
Most reduce nitrate, produce catalase, and oxidize sugars
Some are partially acid-fast

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26
Q

Where is nocarida commonly found?

A

Soil
Decaying vegetation
Compost
Other environmental sources

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27
Q

How does nocardia enter the body?

A

through contamination of wounds or by inhalation

28
Q

What contributes to the virulence of nocardia?

A

Trehalose 6,6’-dimycolate

29
Q

How does trehalose 6,6’-dimycolate contribute to virulence of nocardia?

A

By inhibiting phagosome-lysosome fusion

30
Q

What in nocardia probably mediates resistance to killing by neutrophils?

A

Membrane-bound catalase and superoxide dismutase

31
Q

What may be involved in the pathogenesis of nocardia?

A

A mouse-toxic secreted product of N. otitidiscaviarum

32
Q

What is the first clinical sign of N. asteroides?

A

The appearance of an indurated nodule or pustule, which ruptures and suppurates

33
Q

Where is infection of nocardia often found in cattle?

A

Draining tracts of mammary glands

34
Q

What does nocardia cause when it disseminates from the mammary gland to other organs?

A

Suppurative pleurites or peritonitis

35
Q

What does canine thoracic nocardiosis often involve?

A

Suppurative pleuritis and peritonitis

Abscessation of heart, liver, kidneys, and brain are common

36
Q

What may occur with nocardia in hoses and pigs?

A

Nocardial abortion

37
Q

What nocardia species has been isolated from supparative wounds?

A

N. brasiliensis

38
Q

What nocardia species was named for its occurrence in guinea pig ear infections?

A

N. otitidiscaviarum

39
Q

What nocardia species is associated with bovine farcy?

A

N. farcinica

40
Q

What nocardia species cause granulomatous lesions in salmonid fish?

A

N. salmonicida and N. seriolae

41
Q

What genus have nocardioform actinomycetes from placentitis and abortion in horses in some of areas of the US been placed in?

A

Crossiella, eg, C. equi

42
Q

What can a presumptive diagnosis of nocardia be based on?

A

Pathology and the presence of gram-positive, acid-fast branching, beaded filaments in smears

43
Q

What do colonies of nocradia do?

A

Adhere to the surface of blood or chocolate agar

44
Q

What is the treatment for nocardia?

A

β-lactam antimicrobial agents are not therapeutically effective for any myocardial infection
Udder infusions of novobiocin, combined with nitrofurazone, for 305 days has been successful treatment of bovine nocardial mastitis
Nonmastitic forms can be treated with sulfamethoxazole-trimethoprim, sulfonamides, novobiocin, ampicillin, or tetracyclines

45
Q

Describe actinomyces

A

Gram-positive, non-acid-fast rods, many of which are filamentous or branching
Braches are less than 1 μm in diameter, as opposed to fungal filaments, which are more than 1 μm in diameter

46
Q

What is A. bovis the etiologic agent of?

A

Lumpy jaw in cattle

47
Q

What has A. bovis been isolated from?

A

Abscesses in the lungs of cattle and from infrequent infections in sheep, pigs, dogs, and other mammals, including chronic fistulous withers and chronic poll evil in horses

48
Q

What is lumpy jaw?

A

A chronic, progressive, indurated, granulomatous, suppurative abscess that most frequently involves the mandible, maxillae, or other bony tissues in the head

49
Q

When is disease with A. bovis seen?

A

When it is introduced to underlying soft tissue, via penetrating wounds of the oral mucosa from wire or coarse hay or sticks

50
Q

What can A. bovis result in when it is involved with adjacent bone?

A

Facial distortion
Loose teeth
Dyspnea

51
Q

What indicates the presence of A. bovis?

A

Demonstration of gram-positive rods in yellowish “sulfur granules” rom aspirated purulent material

52
Q

Why is treatment of A. bovis in cases where bone is extensively involved rarely successful?

A

Poor penetration of antibacterial agents

53
Q

What can be effective in less advanced cases of A. bovis?

A

Penicillin

54
Q

What was once successful for systemic treatment of A. bovis, but is no longer recommended due to food safety issues?

A

Potassium iodide

55
Q

What does A. hordeovulneris cause?

A

Localized abscesses and systemic infections, such as pleuritis, peritonitis, visceral abscesses, and septic arthritis in dogs

56
Q

What is a common predisposing factor to A. hordeovulneris?

A

Tissue-migrating foxtail grass

57
Q

What is A. israelii primarily associated with?

A

Chronic granulomatous infection in humans, but has been isolated from pyogranulomatous lesions in pigs and cattle

58
Q

What has A. naeslundii been isolated from?

A

Aborted pig fetuses

59
Q

What has A. (Corynebacterium) pyogenes been reclassified as?

A

Arcanobacterium pyogenes

60
Q

What was the genus of A. (Corynebacterium) pyogenes recently changed to? Why?

A

Trueperella

Genomic findings

61
Q

What are conditions caused by A. (Corynebacterium) pyogenes?

A 
Suppurative mastitis
Suppurative pneumonia
Septicemia
Vegetative endocarditis
Endometritis
Septic arthritis
Wound infections (umbilical infections, seminal vesiculitis, summer mastitis)
Liver abscesses
62
Q

What is the number 1 bacterium in the rumen and reticulum of ruminants and the intestines of pigs?

A

A. (Corynebacterium) pyogenes

63
Q

What does A. suis cause?

A

Pyogranulomatous porcine mastitis

64
Q

What is pyogranulomatous porcine mastitis characterized by?

A

Viscid, yellow pus surrounded by a wide zone of dense connective tissue
Yellow “sulfur granules” may be scattered throughout the pus
Deep seated abscesses may fistulate

65
Q

What can pyogranulomatous infections caused by A. suis develop in?

A

Lungs
Spleen
Kidneys

66
Q

What does A. viscosus cause?

A

Chronic pneumonia
Pyothorax
Localized subcutaneous abscesses in dogs

67
Q

What are thoracic lesions by A. viscosus? Cutaneous lesions?

A

Pyogranulomas

Granulomatous abscesses

Infectious Agents (38 decks)

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