Genus Listeria Flashcards
(28 cards)
Describe the shape and staining properties of Listeria.
Rod shaped, gram +.
What is the oxygen classification of Listeria?
Aerobic organisms.
Describe the pH and temperature range of Listeria.
Tolerates wide pH range: 5.5-9.6; grows at a wide temperature range: 1-45 degrees C.
Listeria is a ____________ bacteria that invades the _____________ of living cells.
Pathogenic, cytoplasm.
Describe Listeria as a facultative intracellular organism.
Develops a distinctive rocket tail structure to help push through the cytoplasm; eventually bacteria are pushed into neighboring cells such as macrophages or non-phagocytic cells to propagate the infection.
Describe the habitat of L. monocytogenes.
On plants and vegetation; soil or water; animal and human feces under the proper environmental conditions and pH.
Listeriosis in animals is mainly caused by what?
Feeding improperly preserved or spoiled silage or spoiled hay.
What are the virulence factors of L. monocytogenes?
Internalins, Listeriolysin O (hemolysin), ActA (Actin A) protein.
What is the role of internalins as a virulence factor of L. monocytogenes?
Mediate adhesion to host cells and cellular engulfment.
What is the role of Listeriolysin O as a virulence factor of L. monocytogenes?
Mediates escape from phagosome.
What is the role of ActA protein as a virulence factor of L. monocytogenes?
Mediates cell-to-cell spread.
Describe the process of pathogenesis of L. monocytogenes.
Adhesion -> invasion -> cell-to-cell spread.
Where does replication of Listeria monocytogenes occur?
M cells and enterocytes.
What are the components of pathogenesis of Listeria monocytogenes?
Replication, spread to adjacent cells, macrophage-associated bacteremia: dissemination of bacteria, meningoencephalitis.
Describe meningoencephalitis with L. monocytogenes.
Infection of cranial nerves or brainstem (medulla and pons).
What are the clinical findings of L. monocytogenes?
Visceral (septicemic) listeriosis, listerial abortion, neural listeriosis (meningoencephalitis: ‘circling disease’).
What happens in the case of neural listeriosis caused by L. monocytogenes?
Unilateral micro-abscesses in the brain stem.
Is L. monocytogenes zoonotic?
Yes, particular concern in pregnant women.
What species do L. monocytogenes affect and what are the main clinical signs in each?
Ruminants: encephalitis, abortion; monogastrics and birds: septicemia; horses: septicemia (neonates); humans: septicemia, abortion and gastroenteritis.
What species do L. ivanovii affect and what are the main clinical signs associated with them?
Sheep and cattle: abortion.
In sheep, listeriosis often causes what conditions?
Abortion at 12 weeks or later, encephalitis, and retained placentas; referred to as listerial abortion.
What will you see physically with the animal in the case of listerial abortion?
Necrotic caruncle, necrotizing placentitis, macerated fetus, fetal brain abscessation.
What are the physical signs you will see in the animal in the case of neural listeriosis?
Unidirectional circling towards the affected side of the brain stem, prolapse of the tongue due to facial nerve paralysis, drooping ears, eyelids, and muzzle due to facial nerve paralysis, meningitis: head pressing.
What bacterial organism is known to cause abortion storms in sheep?
Listeria.
