Actinobacteria Flashcards
What are the major morphological characteristics of Actinobacteria?
Gram-positive bacteria showing filamentous formation and granulomatous lesions in infected animals
How do Nocardia, Actinomyces, Dermatophilus, and Actinobaculum compare in respiration, Ziehl-Neelson staining, growth on Sabouraud dextrose agar, and aerial filament production?
NOCARDIA: aerobic, +, +, +
ACTINOMYCES: anaerobic/facultative anaerobic and capnophilic, -, -, -
DERMATOPHILUS: aerobic and capnophilic, -, -, -
ACTINOBACULUM: anaerobic, -, -, -
What is the predilection site of Arcanobacterium pyogenes, Actinobaculum suis, Actinomyces bovis, and Actinomyces hordeovulneris?
A. pyogenes: nasopharyngeal mucosa
A. suis: preputial mucosa
A. bovis: oropharynx mucosa
A. hordeovulneris: unknown
What kind of hemolysis does Arcanobacterium pyogenes (Trueperella pyogenes) do?
β-hemolysis
What are the major morphological features of Arcanobacterium (Trueperella) pyogenes?
- Gram-positive rod
- pleomorphic
- non-spore forming
- non-motile
- non-capsulated
- facultative anaerobe
What is the characteristic metabolism that Arcanobacterium (Trueperella) pyogenes undergoes? What other strong activity does it have?
fermentative metabolism
strong proteolytic activity
Arcanobacterium (Trueperella) pyogenes is an opportunistic pathogen. Where can it be found in the normal microbiota?
- wall of bovine rumen
- wall of swine stomachs
- bovine GI tract and udders
What kind of lesions does Arcanobacterium (Trueperella) pyogenes cause? What organs are typically affected?
suppurative lesions
any organs —> lymphadenitis, osteomyelitis, peritonitis, neural abscesses, pyometra, mastitis
What is the pathogenesis of Arcanobacterium (Trueperella) pyogenes?
exogenous infection from mechanical injuries of skin and mucous membranes
endogenous infection from internal injury allowing colonies in the microflora to pass through the epithelium and recruit monocytes, neutrophils, DC, and other proinflammatory cells to secrete proinflammatory mediators
What are the major virulence factors of Arcanobacterium (Trueperella) pyogenes that promote adhesion and have hemolytic/cytotoxic activity?
ADHESION: collagen-binding protein, fibrinogen-binding protein, fibronectin-binding protein, neuraminidase H/P
HEMOLYTIC/CYTOTOXIC: pyolysin, proteases, DNAse
Arcanobacterium (Trueperella) pyogenes infection:
Arcanobacterium (Trueperella) pyogenes:
cow, pig, sheep
- suppurative lesion of lungs
What samples from sick animals can be tested for Arcanobacterium (Trueperella) pyogenes? What is the expected histopathological result?
exudates and tissue samples should show filamentous organisms surrounded by filamentous club-shaped structures
How does Arcanobacterium (Trueperella) pyogenes grow on blood agar? How does it show up on a Gram stain?
β-hemolytic
Gram-positive, short, pleomorphic rods
What 4 vaccines of Arcanobacterium (Trueperella) pyogenes have been developed?
- whole cells of Arcanobacterium (Trueperella) pyogenes or culture supernatant
- recombinant: fimbria H, PLO, leukotoxin
- DNA vaccine
- autovaccine
What causes canine actinomysis? What is the characteristic lesion? Main clinical sign? Treatment?
Actinomyces viscosus
subcutaneous pyogranulomatous lesions and extensive fibrovascular proliferation on the peritoneal or pleural surfaces with anguine-purulent exudate in the affected cavity
respiratory distress
penicillin
What is another name for bovine actinomycosis? What causes it?
lumpy jaw
Actinomyces bovis
What allows for bovine actinomycosis to develop? What does this cause?
infected trauma or lesion of the oral mucosa/dental alveoli
swelling of the bone and fistulous tract formation with purulent exudate
How is bovine actinomycosis diagnosed? Treated?
clinical signs, X-rays
penicillin
Bovine actinomycosis:
lumpy jaw, A. bovis
Bovine actinomycosis, exudate:
What causes porcine cystitis? Where can it be isolated from? How does it grow on blood agar and look microscopically?
Actinobaculum suis
prepuce and preputial diverticulum
γ-hemolytic
Gram-positive pleomorphic rods with acute angle arrangements
What are the common clinical signs of porcine cystitis? When can it be deadly?
anorexia, arching back, dysuria, hematuria
when it affects the kidneys
What are Nocardia spp.? What 2 cultures do they grow on?
Gram-positive, aerobic, saprophytic actinobacteria with filamentous morphology
- blood agar
- culture medium with charcoal-yeast extract
What do Nocardia spp. look like when cultured? What can Nocardia spp. be subcultured on and how do they look different?
white, powdery, and firmly adherent to the agar
Sabouraud dextrose agar - dru, wrinkled, orange-colored colonies after 5 days of incubation
What is an important predisposing factor for Nocardia infections? What does infection cause in cattle and sows?
immunosuppression
sporadic mastitis
abortion
How do dogs develop canine nocardiosis? What are the 3 forms and how do they present?
inhalation, through skin wounds, ingestion
- THORACIC: fibrovascular proliferative reaction on the pleura and anguinopurulent fluid accumulation - respiratory distress
- CUTANEOUS: ulcer; granulomatous swelling with discharging fistulous tracts
- DISSEMINATED: non-specific clinical signs in dogs less than 12 mos; referable to organ system mainly affected
What are 2 common treatments of canine nocardiosis?
- wide spectrum Amikacin
- cotrimoxazole
What is bovine farcy? What environment is infection limited to?
bovine nocardiosis - chronic infection of superficial lymphatic vessels and lymph nodes causing an increase in their size and thickness
tropics
How does bovine farcy develop?
- early lesions consist of small cutaneous nodules often on the medial aspect of the legs and on the neck
- nodules enlarge slowly and coalesce to form swellings up to 10 cm in diameter, which can rarely ulcerate
What happens to lymphatic vessels in bovine farcy? How do internal organ lesions compare to other diseases?
become thickened and cord-like
lesions resemble those of tuberculosis
Dermatophilus congolensis can be found worldwide. Where is it most commonly a problem?
tropics and subtropics
What is the overall morphology of Dermatophilus congolensis? Where can they be usually found? What causes infection?
Gram-positive, filamentous motile coccal zoospores (look like spermatoyctes)
persist in skin
dormant zoospores become activated in moist and warm environments
What conditions are favorable for Dermatophilus congolensis infection? What does it cause? What increases host susceptibility?
traumatic injury and wet conditions, heavy and prolonged rainfall
acute inflammatory response and micro-abscesses in the epidermis, large crust formation leading to permanently damaged skin
current disease, pregnancy, Amblyomma variegatum-caused lesion
Dermatophilus congolensis infection is more prevalent in what animals? How are zoospores transmitted?
young animals, especially ruminants
direct contact with infected animals and blood-sucking insects
What is the main way that Dermatophilus congolensis infection is diagnosed?
scab material and samples of skin fixed in formalin sent to lab where the undersurfaces are smeared and stained by the Giemsa method, revealing characteristic branching filaments containing zoospores
What do colonies of Dermatophilus congolensis look like?
1 mm in diameter, yellow and hemolytic
becomes rough, golden-yellow, and embedded in agar when incubated for 3-4 days
How is Dermatophilus congolensis infection treated?
Oxytetracycline
What is Corynebacterium?
fastidious, Gram-positive pleomorphic bacteria that is a common part of the commensal microflora (opportunistic) and are non-motile, facultative anaerobes
How does Corynebacterium test for catalase and oxidase?
+, -
What causes Corynebacterium infection? How is disease identified?
tissue trauma —> infection —> suppurative lesion
host specific —> clinical diagnosis can be made based on characteristic lesions of each genus
What are 2 major genera of Corynebacterium and what diseases do they cause?
- C. bovis - subclinical mastitis in cattle, caseous lymphadenitis
- C. pseudotuberculosis - caseous lymphadenitis in sheep and goats (non-nitrate reducing); ulcerative lymphangitis, abscesses (nitrate reducing)
What are the 3 types of Corynebacterium renale group? What disease does each cause?
TYPE I: C. renale - cystitis, pyelonephritis in cattle
TYPE II: C. pilosum - ulcerative (enzootic) balanoposthitis in sheep and goats
TYPE III: C. cystitidis - severe cystitis, rarely pyelonephritis in cattle
How do the colonies of Corynebacterium bovis, kutscheri, pseudotuberculosis, and renale compare morphologically?
C. bovis - small, white, dry, non-hemolytic in bovine milk samples
C. kutscheri - whitish, sometimes hemolytic
C. pseudotuberculosis - small, whitish, surrounded by a narrow zone of complete hemolysis —> become dry, crumbly, and cream
C. renale - small, non-hemolytic
FASTIDIOUS - hard to grow
What enzymes enhance the virulence of Corynebacterium pseudotuberculosis?
phospholipase D, protease 40
What is the major characteristic of lesions caused by Corynebacterium?
pyogenic - suppurative conditions
Caseous lymphadenitis:
C. bovis
C. paratuberculosis
Bovine pyelonephritis:
C. renale
(dysuria)
Ulcerative balanophosthitis:
C. renale
What is Rhodococcus equi? Where is it commonly found? What major disease does it cause?
Gram-positive rods or cocci that are aerobic and non-motile
inhabitant of soil (saprophyte) and GI tract
suppurative pneumonia of foals
What is the CAMP test? How does Rhodococcus equi test?
Rhodoccocus equi produces a factor that is able to lyse red blood cells that have been previously damaged by beta-hemolysin of Staph. aureus, so when streaked perpendicular to a streak of Staph. aureus, a spade-shaped area of complete hemolysis should be produce
(+)
What is the characteristic clinical sign of Rhodococcus equi infection? Some additional signs?
loud, moist rales on lung ascultation
- fever
- anorexia
- bronchopneumonia (cough, dyspnea, weight loss, exercise intolerance)
How can Rhodococcus equi infection be diagnosed? What are 2 possible treatments?
- history of disease on the farm
- leukocytosis
- ultrasonography of thorax
- Rifampin
- Erythromycin
What is the major characteristics of Mycobacteria? What is their cell wall made out of?
Ziehl-Neelson (acid fast) positive rods that are aerobic and require a complex egg-enriched media for growth
rich in complex lipids and waxes containing mycolic acids - makes it resistant to chemical disinfectants and environmental influences, but susceptible to heat treatment
What 5 major diseases are cause by Mycobacteria?
- tuberculosis in avian and mammalian species
- Johne’s disease (paratuberculosis) in ruminants
- feline leprosy
- skin tuberculosis and bovine farcy
- granulomatous lesions
Is Mycobacterium infection acute or chronic?
chronic
What supplement is required to isolate M. avium subsp. paratuberculosis?
mycobactin from other bacteria
What causes tuberculosis in cattle? What makes eradication difficult?
Mycobacterium bovis
- M. bovis can affect wildlife and be spread
- M. avium and other saprophytic mycobacteria can also infect bovines (when infected, must be culled)
How do animals become infected with Mycobacterium bovis?
infected animal (bovines, pigs, cats, wildlife) infect healthy animals via aersol/ingestion, which reaches the lungs of the healthy animal and generates infective aerosols
What is the pathogenesis of Mycobacterium bovis?
- bacteria in respiratory tract
- survives in lungs and multiplies in host macrophages and DC
- infected macrophages accumulate in lungs
- inflammatory cytokine production causes a cellular immune response that is not enough to remove the pathogen, so it is remains
- continuous response causes the formation of granulomas
- can be spread to lymph nodes
When are the clinical signs of tuberculosis in cattle apparent? What are some signs?
advanced disease —> those with extensive lesions can appead to be in good health
- loss of condition
- cough
- intermittent pyrexia
- marked induration of affected quarters
- supramammary lymph node enlargement
- masitis, contaminated milk (pasteurization)
How is tuberculosis in cattle diagnosed?
- tuberculin test
- IFN-gamma assay (marked increase)
- ELISA (however, mostly cellular response), PCR
- lesion samples histopathology (granuloma, ZN+)
- isolation of M. bovis
- lymphocyte proliferation/cytotoxicity
How is tuberculosis in cattle controlled?
- no treatment —> infected are culled
- disinfection of farm/buildings
- keeping wildlife away from farm
- human vaccines: BCG (heterologous), DNA vaccine, mycobacterial proteins
What false positives, false negatives, and cross reactions are possible with the tuberculin test?
FALSE +: Mycobacterium phlei
FALSE -: animals with advanced tuberculosis (IgG), test done at early stage of infection
CROSS REACTIONS: Mycobacterium avium, Mycobacterium paratuberculosis, Nocardia spp.
What is the most common way that the tuberculin test is done?
intradermal —> simple, prone to false positives, poor sensitivity
Delayed hypersensitivity reaction (tuberculin):
antigen —> DC (langerhans) —> lymph node —> T cells —> chemokines and cytokines activate basophils and macrophages to induce inflammation within 24-48 hours
Bovine tuberculosis:
granulomas —> caseous
(ZN+)
What causes avian tuberculosis? In what birds is it most common? What are some clinical signs?
Mycobacterium avium
adult birds (chronic disease)
- non-specific: dullness, emaciation, lameness
- granuloma lesions in liver, spleen, bone marrow, intestine
Can Mycobacterium cause tuberculosis in animals other than birds?
yes - immunocompromised humans
rare in cats, dogs, horses, and pigs
How is avian tuberclosis diagnosed?
- tuberculin testing using M. avium (PPD)
- macroscopic lesions
- ZN staining (+)
Avian tuberculosis:
M. avium
(gramuloma)
What causes feline lepsosy? How is it transmitted to cats? What are the characteristic lesions?
Mycobacterium lepraemurium
sporadically transmitted to cats through bites from infected rodents
nodular lesions in subcutaneous tissues, especially on head and limbs
How is feline leprosy diagnosed?
tissue samples —> histopathology = ZN+, granuloma
What causes Johne’s disease (paratuberculosis? What animals are most susceptible? How do these animals become infected?
Mycobacterium avium subsp. paratuberculosis
calves (clinical disease rarely encountered in cattle under 2 years old - subclinical shedding of mycobacterium in feces)
oral ingestion of organisms shed in feces of infected animals or pooled contaminated colostrum
What is the pathogenesis of Johne’s disease (paratuberculosis)?
- intracellular pathogen (Mycobacterium avium subsp. paratuberculosis)
- ingested mycobacteria are taken up by M cells in the intestine
- organisms cross the intestinal epithelial layer
- engulfed by macrophages in which they survive and replicate
- interferes with maturation of phagosome-lysosome fusion
- granuloma formation in lamina propria and submucosa of the GI tract
- enteropathy leads to loss of plasma proteins and malabsorption of nutrients and water
When do cattle affected by Johne’s disease show clinical signs? What are some of these signs?
after 2 years of age
- persistent and profuse diarrhea
- weight loss
- mucosa terminal small intestine and large intestine is thickened and folded into transverse corrugations
- mesenteric and ileocecal lymph nodes enlargement and edematous
How is Johne’s disease diagnosed?
- direct microscopy from live animal samples (biopsy), histopathology, ZN+, bacterial isolation
- postmortem: tissue samples from affected intestines and mesenteric lymph nodes
- serology: complement fixation, ELISA, immunodiffusion, IFN-gamma assay
- Johnin intradermal test
- PCR
How is Johne’s disease controlled?
- isolate sick animals
- facility hygiene
- inactivated and live attenuated vaccines
