Actinomyces/Nocardia/Dermatophilus

Question 1

What are the morphologic characteristics of actinomycetes?

Answer 1

• Gram positive rods
• non-motile
• Non-spore forming
• Extensive filamentation and branching looks like fungi and they form granulomatous lesions

Question 2

How are Actinomyces, Nocardia and Dermatophilus fungi-like?

Answer 2

• Nocardia resemble Mycobacterium because of similarities in complex cell wall components
• Actinomyces and Dermatophilus are similar to Nocardia but they are not partially acid-fast

Question 3

How are Actinomyces transmitted?

Answer 3

• Commensal
• Infection due to mucous membrane trauma
• Infections resulting from virus or other bacteria

Question 4

How are Nocardia spp transmitted?

Answer 4

• Inhalation
• Wound contamination

Question 5

How are Dermatophilus spp. transmitted

Answer 5

• Direct contact
• Contaminated inanimate objects

Question 6

What is the pathogenesis of Actinomycetes?

Answer 6

• Not highly virulent
• Cause opportunistic and chronic infections
  
  • spread slow and progressively
• Form suppurative granulomatous lesions

Question 7

What is Actinomyces bovis?

Answer 7

• Oral cavity commensal
• Enters through damaged mucous membranes
  
  • oral cavity and upper digestive tract
• Development of hardened granulomatous and suppurative lesions
  
  • bone and soft tissue “Lumpy Jaw”
  • mandible and other tissue of the head
  • Yellowish “sulphur granules”
    
    • Bacteria embedded in tissue

Question 8

What is Actinomyces bovis?

Answer 8

• Oral cavity commensal
• Enters through damaged mucous membranes
  
  • oral cavity and upper digestive tract
• Development of hardened granulomatous and suppurative lesions
  
  • bone and soft tissue “Lumpy Jaw”
  • mandible and other tissue of the head
  • Yellowish “sulphur granules”
    
    • Bacteria embedded in tissue

Question 9

What complications can Actinomyes bovis cause?

Answer 9

• Swallowed - Systemic infection
  
  • visceral actinomycosis
  • abdominal actinomycosis
• Reaches lungs
  
  • Pulmonary actinomycosis
• Lesions in the liver and other organs
  
  • Orchitis
  • Mastitis

Question 10

How is Actinomyces bovis diagnosed?

Answer 10

• Gross pathology - “sulfur granules”
• Granules in pus
  
  • branching G+ filaments
• Culture and Biochemical tests
  
  • definitive

Question 11

How is Actinomyces bovis treated?

Answer 11

• Treat early - likely to recover
• Iodine & tetracyclines
• Surgical drainage and irrigation of open abscesses with iodine solution

Question 12

What does Actinomyces bovis cause in swine?

Answer 12

• Abscesses in liver and other organs
• Chronic granulomatous suppurative mastitis and orchitis

Question 13

What are Actinomyces viscosus & israelii?

Answer 13

• Cause infections in humans
  
  • Lesions on face, neck, lung, breast, and lymph nodes
• Cause infections of oral cavity in dogs and cats
  
  • Granulomatous abscesses common in thorax, abdomen

Question 14

What is Nocardioses?

Answer 14

• Nocardia asteroides
• Non-contagious
• Exogenous infection from soil
  
  • trauma or implantation of foreign body or wound contamination forms pustule
  • Subsequent induration, rupture and spread for additional abscesses
• Chronic progressive
• Sporadic infections of cattle, dogs, cats, horses, and humans

Question 15

What does Nocardia asteroides cause in cattle?

Answer 15

• Acute or chronic disease
• Mastitis with granulomatous lesions
• Draining fistulous tracts

Question 16

What does Nocardia asteroides cause in dogs/cats?

Answer 16

• Subcutaneous lesions (mycetomas)
• Lesions in throat, abdome, heart, brain, liver, and kidneys
• Severe halitosis, gingivitis, and ulceration of the oral cavity is common in dogs

Question 17

What does Nocardia asteroides cause in horses?

Answer 17

• Infrequent infection
• seen in immunosuppressed

Question 18

What does Nocardia asteroides cause in humans?

Answer 18

• Pulmonary and subcutaneous forms
• Systemic disease with CNS involvement is fatal

Question 19

What does Nocardia asteroides cause in swine?

Answer 19

• rare
• pneumonia
• abortion
• lymphadenitis

Question 20

What does Nocardia asteroides cause in avian species?

Answer 20

• rare
• respiratory problems

Question 21

How is Nocardiosis Diagnosed?

Answer 21

• Presumptive:
  
  • Pathology
  • Demonstration of typical organisms
• Gram / Acid-fast stain
  
  • Branching filaments
• Growth on blood agar:
  
  • slow, 4-5 days
  • Irregularly folded, granular white to yellow colonies

Question 22

How is Nocardiosis treated?

Answer 22

• Surgical drainage of lesions
• Sulfa drugs, ampicillin, tetracyclines, amikacin, cefotaxime
  
  • Prolonged (months)

Question 23

What is Dermtophilus congolensis?

Answer 23

• Obligate, facultative
• Gram-positive filamentous
• Found on skin
• Can be fatal for calves, sheep, and goats if complicated
• Associated with Amblyomma variegatum (tick) in Caribbean islands

Question 24

What does Dermtophilus congolensis cause in sheep?

Answer 24

• Mycotic dermatitis in 3 forms:
  
  • Wool - lumpy wool
  • Face and scrotum
  • Lower leg and foot - strawberry foot rot

Question 25

Is Dermatophilus congolensis zoonotic?

Answer 25

• Yes
• acquired from farm animals

Question 26

How is Dermatophilus congolensis diagnosed?

Answer 26

• Gram / Giemsa stain scab smears
  
  • segmenting filaments and coccoid bacteria
  • stain deep purple
• Growth on Blood agar
  
  • small, rough, grayish-white colonies in 1-2 days
• Immunofluorescent staining
• Persistent infection
  
  • protected from second infection if cleared

Question 27

How is Dermatophilus congolensis treated?

Answer 27

• Penicillin and Streptomycin
• Tetracyline and chloramphenicol also effective
• Remove scabs, wash with mild soap, topical application of iodine compound or copper sulfate