Actinomyces/Nocardia/Dermatophilus Flashcards
What are the morphologic characteristics of actinomycetes?
- Gram positive rods
- non-motile
- Non-spore forming
- Extensive filamentation and branching looks like fungi and they form granulomatous lesions
How are Actinomyces, Nocardia and Dermatophilus fungi-like?
- 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
How are Actinomyces transmitted?
- Commensal
- Infection due to mucous membrane trauma
- Infections resulting from virus or other bacteria
How are Nocardia spp transmitted?
- Inhalation
- Wound contamination
How are Dermatophilus spp. transmitted
- Direct contact
- Contaminated inanimate objects
What is the pathogenesis of Actinomycetes?
- Not highly virulent
- Cause opportunistic and chronic infections
- spread slow and progressively
- Form suppurative granulomatous lesions
What is Actinomyces bovis?
- 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
What is Actinomyces bovis?
- 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
What complications can Actinomyes bovis cause?
- Swallowed - Systemic infection
- visceral actinomycosis
- abdominal actinomycosis
- Reaches lungs
- Pulmonary actinomycosis
- Lesions in the liver and other organs
- Orchitis
- Mastitis
How is Actinomyces bovis diagnosed?
- Gross pathology - “sulfur granules”
- Granules in pus
- branching G+ filaments
- Culture and Biochemical tests
- definitive
How is Actinomyces bovis treated?
- Treat early - likely to recover
- Iodine & tetracyclines
- Surgical drainage and irrigation of open abscesses with iodine solution
What does Actinomyces bovis cause in swine?
- Abscesses in liver and other organs
- Chronic granulomatous suppurative mastitis and orchitis
What are Actinomyces viscosus & israelii?
- 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
What is Nocardioses?
- 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
What does Nocardia asteroides cause in cattle?
- Acute or chronic disease
- Mastitis with granulomatous lesions
- Draining fistulous tracts
What does Nocardia asteroides cause in dogs/cats?
- 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
What does Nocardia asteroides cause in horses?
- Infrequent infection
- seen in immunosuppressed
What does Nocardia asteroides cause in humans?
- Pulmonary and subcutaneous forms
- Systemic disease with CNS involvement is fatal
What does Nocardia asteroides cause in swine?
- rare
- pneumonia
- abortion
- lymphadenitis
What does Nocardia asteroides cause in avian species?
- rare
- respiratory problems
How is Nocardiosis Diagnosed?
- 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
How is Nocardiosis treated?
- Surgical drainage of lesions
- Sulfa drugs, ampicillin, tetracyclines, amikacin, cefotaxime
- Prolonged (months)
What is Dermtophilus congolensis?
- 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
What does Dermtophilus congolensis cause in sheep?
- Mycotic dermatitis in 3 forms:
- Wool - lumpy wool
- Face and scrotum
- Lower leg and foot - strawberry foot rot
Is Dermatophilus congolensis zoonotic?
- Yes
- acquired from farm animals
How is Dermatophilus congolensis diagnosed?
- 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
How is Dermatophilus congolensis treated?
- Penicillin and Streptomycin
- Tetracyline and chloramphenicol also effective
- Remove scabs, wash with mild soap, topical application of iodine compound or copper sulfate
