Lecture 7 - Gram Pos Rods (pt.1)

What are the key virulence factors of B. anthracis?

Anti-phagocytic D-glutamic acid capsule + tripartite exotoxin (edema factor, lethal factor, protective antigen)

What stain shows the capsule of B. anthracis?

McFadyean's methylene blue (blue rods with pink capsule)

How are anthrax spores transmitted?

Ingestion, inhalation, skin contact; spores persist for decades in soil

Where is the antiphagiocytic capsule produced in Bacillus anthracis?

in vivo only

What does anthrax toxin cause?

increased vascular permeability and cell necrosis

What is required from anthrax to be virulent?

both capsule and toxin

Pathogenesis of anthrax

spore entry --> germination and spred to LN --> enters blood stream --> toxin injures/kills neutrophils and macrophages --> replication in blood --> toxin causes inflammation from macrophages and fluid loss --> death from septic shock

What factors predispose animals to Listeria monocytogenes exposure?

Feeding poor-quality silage (esp. winter/spring)

What are the clinical signs of "circling disease" in cattle?

Unilateral facial paralysis, drooping eyelid/ear, circling, purulent endophthalmitis

What forms of disease does Listeria monocytogenes cause?

Encephalitis (ruminants), septicemia (young/monogastrics), abortion, gastroenteritis

How is listeriosis diagnosed?

History/clinical signs; postmortem brain microabscesses; culture brainstem, liver, spleen, feces culture

What is the treatment and prevention of listeriosis?

Penicillin (drug of choice), ampicillin + gentamicin; no vaccines; avoid poor silage

What is the zoonotic concern with Listeria?

Causes meningitis, septicemia, abortion in pregnant women/neonates; foodborne outbreaks

Where is Erysipelothrix found?

Tonsils and intestines of animals; resistant in environment

What are the clinical forms of swine erysipelas?

Acute/subacute septicemia with diamond skin lesions; chronic endocarditis and polyarthritis

What diseases does Erysipelothrix cause in other species?

Turkeys: septicemia, endocarditis, arthritis

Sheep: polyarthritis ("post-dipping lameness")

Humans: erysipeloid cellulitis (occupational hazard)

How is Erysipelothrix diagnosed?

Aerobic culture of blood/organs (not skin); PCR

What is the treatment and control for swine erysipelas?

Penicillin, tetracycline; intrinsic resistance to vancomycin/aminoglycosides; vaccination in pigs/turkeys

What are common forms of anthrax?

per acute septicmia - ruminants

acute septicemia - horse

pulmonary - human (wool sorters disease)

pharyngeal - pigs, dogs

intestinal - human, pig, horse

cutaneous - men (malignant carbuncle)

What is the order of disease severity (anthrax)?

cow --> sheep --> horse --> goat --> dog --> pig

What are antemortem and post mortem signs of per acute/acute anthrax?

antemortem- high fever, bleeding from orifices, respiratory distress

postmortem - large, jelly like spleen (splenomegaly), widespread edema, dark unclotted blood, incomplete rigor mortis

80% of becteria in blood

What kind of bacteria is Listeria monocytogenes?

faculative intracellular and capable of growing in cold temeprature

What is a virulence factor of Listeria monocytogenes?

Act A - intracellular movement to adjacent cells through bacterially induced host actin polymerization

What does Listeria monocytogenes cause in young ruminants and monogastrics?

focal hepatic necrosis

What causes human eysipeloid?

Group A beta-hemolytic streptococci