Actinomycetales Flashcards
Actinomycetales characteristics
-biocontainment level 1-2
-gram positives
Actinomyces, and Nocardia genera
-microaerophilic or anaerobic
-non spore forming
-filamentous rods
-Nocardia has similar cell wall to mycobacterium and is acid fast
-branching filaments
Trueperella pyogenes
-Pleomorphic (variable shapes) gram positive coccobacilli
Dermatophilus congolensis
-one of only two species in the genus
-characteristic tram track appearance on cytology
>gram positive zoospores in parallel lines two across
>free living individual coccoid elements also visible
-pleomorphic in pure culture
Streptomyces spp
-soil organisms
-source of many useful natural products
>antibiotics (eg. streptomycin, neomycin)
>parasiticides (eg. ivermectin)
-chemotherapeutic agents (eg. Bleomycin)
Host of Actinomyces and Trueperella
-host associated- mucous membranes, nasal cavity, pharynx
Dermatophilus congolensis habitat
-maintained by carrier animals; on skin
Nocardia and streptomyces habitat
-environmental
Differentiated species taxonomy
- Filamentous rods + acid fast= nocardia
2.filamentous rods. not acid fast, granules present= actinomyces - Not filamentous rods, tram tracks= D. congolensis
- Not filamentous rods, small rods= T. pyogenes
Virulence factors of actinomyces spp
-not well defined
Virulence factors of Trueperella pyogenes
-Pyolysin (cytotoxin) which work against neutrophils, and can be dermonecrotic in lab animals
-Neuraminidases, collagen binding proteins and fimbriae help with adhesion
Virulence factors of Dermatophilus congolensis
-Have proteases to help with tissue breakdown
Virulence factors of Nocardia
-Facultative intracellular parasites, growing in polymorphonuclear neutrophils, inhibit phagosome-lysosome fusion in macrophages
Clinical significance of Actinomyces bovis
-In cattle, normally present in oral microbiota but they enter with invasion of damaged tissue (course feed, plant awns)
-lumpy jaw= mandibular lesions
>periosteal new bone formation in response to infection, fibrosis, hard immovable painless masses, may develop draining tracts
Treatment of actinomyces bovis/lumpy jaw
**lumpy jaw becomes painful when teeth are involved, and they become reluctant to eat
Treat with debridement and antimicrobials (disinfectants for draining tracts, and penicillin)
Treatment can stop growth, but lesion regression will be minimal.
Prevention=use high quality feed
Clinical significance of Actinomyces spp or Norcardia spp in dogs and cats
-Many different actinomyces spp involved. Can cause pyothorax, sub cutaneous infections, foreign body associated infections
-Occur when normal microbiota enters in through wounds (bites, penetrating grass, foreign bodies, stick wounds, damage to oropharynx)
-common in mid-large breed hunting or sport breed dogs
Presentation of Actinomyces spp in dogs and cats
Variable.
-pyothorax, pulmonary if grass aspiration, abdominal id foreign body migrates
-usually head/cervical region, firm or fluctuant lesions, draining tracts
-Abscess fluid (seroanguinous to purulent, contain sulfur granules, filamentous rods may be present)
Treatment of Actinomyces spp in dogs and cats
remove foreign body, treat with long term antimicrobials (penicillin
Clinical significance of Actinobaculum suis in pigs
-commensals of urogenital tracts that can cause UTIs
-can progress to pyelonephritis (kidney infections, can cause rejection at slaughter)
Clinical signs of actinobaculum suis in pigs
-typically afebrile
-hematuria and pyuria
-may be found dead from acute renal failure
Treatment of actinobaculum suis in pigs
-antimicrobials (penicillins)
-management (high hygiene, ensure sufficient access to water)
Clinical significance of Dermatophilus congolensis in horses and cattle
-occurs when carrier animal present, abundance of moisture occurs and causes zoospore release which can infect when skin damage present present.
-Causes superficial infections= Rain scald
Clinical significance of Dermatophilus congolensis in sheep
-Lumpy wool or mycotic dermatitis when on skin
- strawberry foot rot on distal extremities
D. congolensis treatment in sheep and cattle
-topical disinfectants
-antimicrobials
Management: remove from wet environment, AND discard crusts because it is a source of infection for other animals
Clinical significance of Dermatophilus congolensis in dogs and cats
-Dermatophilosis= exudative skin disease
Dogs: superficial on haired skin
Cats: often abscessation
Treatment of D. congolensis in dogs and cats
-keep skin dry and clean
-bathing and crust removal
-antibiotics (penicillins)
Clinical significance of Trueperella pyogenes in cattle, pigs, sheep
-No classical presentation= suppurative infections, laryngeal and liver abscesses, foot rot, specific arthritis
-Polymicrobial infections= Often occurs alongside fusobacterium necrophourm
How does Trueperella pyogenes spread?
-spread through septic emboli
Liver abscess and septic emboli from T. pyogenes
- cattle fed highly fermentable diet
- rumenitis results from lactic acidosis
- translocation of rumen microbes into portal venous system and cause abscess in caudal vena cava, and liver
- Septic emboli spread through venous system to right side of heart and into lungs
- Bacteria get stuck in capillary beds and set up secondary sites of infection
Sample collection of actinomycetales
-Collected for culture and microscopy: exudates, aspirates, fluid aspirates from thoracocentesis, crusts, mastitic milk
-Histopathology- granuloma biopsies
Sample handling of actinomycetales
-For histology, fix in 10% formalin
-do not freeze
Lab ID from smears of aspirates
-Filamentous rods- looking for gram positive and/or acid fast
-granules in pus= actinomyces spp
-tram tracks= Dermatophilus congolensis
Lab ID from culture
-Actinomyces grow well on blood agar (carboxyphilic, 2-4 days)
-Sequencing for specific ID is gold standard; difficult to species ID otherwise
-MALDI useful but not great at species ID
Zoonoses of actinomycetales
**none super risky!
-Actinomyces spp
-Trueperella pyogenes
-Dermatophilus congolensis
Actinomyces spp as a zoonosis
-commonly part of oral microbiota
-disease not classically transmitted from animals
Trueperella pyogenes as a zoonosis
-human infections are rare, not major concern
Dermatophilus congolensis as a zoonosis
-skin infections possible in people who are in contact with infected animals and have a skin trauma, possibly insect bites
Treatment options
- Actinomyces: penicillins
- Nocardia spp: sulfonamides or sulfa/trimethoprim
- Trueperella pyogenes: penicillins, tetracyclins
***avoid metronidazole
Serosanguinous
contains both blood and serous fluid
