Lecture 7 9/25/23 Flashcards
What is the main defining feature of Bacillus sp.?
endospore-forming rods
Which Bacillus species is of great importance, and what does it cause?
B. anthracis, which causes anthrax
What are the characteristics of B. anthracis?
-sporadic cases
-most seen in cattle
-transmit through soil contaminated with spores
-biological warfare agent
What are the two virulence factors of B. anthracis?
-anti-phagocytic capsule
-tripartite exotoxin
Why is the anti-phagocytic capsule of B. anthracis a diagnostic feature?
the polychromatic methylene blue capsule stain will stain the capsule as a pink shadow
What are the three proteins in the tripartite toxin?
-edema factor
-lethal factor
-protective antigen
What does the anthrax toxin do?
increases vascular permeability and cell necrosis
Which B. anthracis strains are virulent?
only those that are both encapsulated and toxigenic (contain both virulence factors)
How is B. anthracis transmitted?
ingestion, inhalation, or skin contact with endospores
What is important about B. anthracis longevitity?
spores can persist in the soil for decades
What are the predisposing factors for anthrax cases?
-previous anthrax deaths
-flooding that causes soil rearrangement
-alkaline, calcium- and nitrogen-rich soils
-warm temps
-drought conditions that cause closer foraging
What type of anthrax do ruminants develop?
per-acute septicemia
What is the order of severity for anthrax disease in animals?
-cattle
-sheep
-horses
-goats
-dogs
-pigs
What is the clinical manifestation of anthrax in cattle?
found dead with un-clotted, dark bloody fluid coming from orifices
What are the signs of anthrax?
-high fever
-bleeding
-shock
-resp. distress
-dark, un-clotted blood
-large, gelatinous spleen
What should you do if you suspect an animal died of anthrax?
-do not conduct a field necropsy
-inform necessary official/report disease
How can anthrax be diagnosed?
-examination of peripheral blood smears stained with polychromatic methylene blue
-cultures
-PCR
How can anthrax be controlled?
vaccination
-proper carcass disposal
-prophylactic antimicrobial therapy
Which listeria sp. is of importance?
Listeria monocytogenes
What are the important characteristics of Listeria sp.?
-facultative intracellular
-capable of growing at 4 deg. C
What are the virulence factors associated with Listeria sp.?
-internalin: adhesion, entry, phagocytosis
-listeriolysin O: req. for intracellular rep.
-Act A: allows intracellular movement to adjacent cells
Why is Act A an important virulence factor?
movement from cell to cell intracellularly helps keep the bacteria undetected by the immune system
What are the potential outcomes of Listeria infection?
-local cell death and focal microabscesses in brain
-septicemia
What causes Listeria infection in ruminants?
feeding poor-quality, infected silage
What are the clinical signs of Listeria circling disease/brain infection?
-unilateral trigeminal and facial nerve paralysis
-purulent endophthalmitis
Which species commonly develop septicemia as a result of Listeria infection?
-humans
-monogastrics
-newborn animals
What are the major lesions of septicemic listeriosis in monogastrics and young ruminants?
-focal hepatic necrosis
-hemorrhagic gastroenteritis
How can Listeria sp. be diagnosed?
-history and symptoms
-visualization of microabscesses on histology
-Listeria enrichment culture
What are the characteristics of Listeria treatment and prevention?
-not attempted with CNS disease
-treated with penicillin or ampicillin/gentamicin combo
-no vaccine
-avoid poor silage (animals) and high risk foods (humans)
What are the characteristics of Erysipelothrix rhusiopathiae?
-most common in pigs and turkeys
-pigs are important reservoirs
What condition is caused by Erysipelothrix sp. in pigs?
-diamond skin disease/swine erysipelas
-vasculitis of blood vessels
What causes outbreaks of Erysipelothrix sp. in sheep?
dipping sheep in contaminated solutions following shearing
How do human erysipeloid and human erysipelas differ?
-human erysipeloid is caused by Erysipelothrix sp.
-human erysipelas is caused by Strep. sp.
How can Erysipelothrix sp. be diagnosed?
-aerobic culture of blood and organs
-PCR
What antibiotics are Erysipelothrix sp. intrinsically resistant to?
-vancomycin
-aminoglycosides
-sulphonamides
How can Erysipelothrix sp. be controlled?
-treatment/isolation of infected animals
-culling
-good hygiene
-vx
