Listeria Flashcards
What are the 2 major species of Listeria of veterinary importance? What animals do they mostly affect?
L. monocytogenes
L. ivanovii
Ruminants (sheep)
What are the 2 major species of Listeria of veterinary importance?
- L. monocytogenes***
- L. ivanovii
How does Listeria stain? What morphologies do they undertake?
Gram positive
rod/bacilli
What respiration does Listeria undergo? Do they form spores?
facultative anaerobe
non-spore forming
How does Listeria respond to the catalase test?
catalase positive
Does Listeria have motile abilities? How is it tested?
yes - has flagella
tumbling motility and umbrella-shaped colony growth in a semi-solid motility media
What function do Listeria’s flagella have?
actin jet motility inside of host cell
How does Listeria grow on blood agar? In what 2 unique environments is Listeria able to grow in?
β-hemolytic
- resistant to high salt in environment
- able to grow at cold temperatures (4 degrees C)
What are the 14 different serotypes of Listeria based on? What 3 serotypes are the most virulent?
based on their different somatic (O) and flagella (H) antigens
- 1/2a = isolated from food
- 1/2b
- 4b = majority of human epidemics
What is the optimal agar for Listeria growth?
Mullen-Hinton agar enriched with 5% sheep blood
What are the 2 key issues with isolating Listeria on a culture media?
- requires an enriched media, since it is fastidious (β-hemolytic; ferments carbohydrates, producing acid and no gas)
- requires prolonged incubation time for the recovery of the stressed cells (at 4 degrees C for weeks; usually weakened or injured cells will not grow)
How are weak and injured Listeria isolated?
- put in 2 possible enrichment broth media: FDA BAM or ISO 11290
- after 4 hours selective agents, like acriflavin, nalidixic acid, and antifungal cycloheximide, are added to sample broth
- incubate FDA BAM for 48 hrs at 30 degrees C amd ISO 11290 for 24 hrs at 30 degrees C
- add full selective secondary-enrichment full concentration Fraser broth for 24 hrs
- spread plate on Listeria selective agar
What 3 Listeria adaptions make it really hardy?
- resistant to high salt in media
- survive and multiply on inanimate objects (silage through transition processes from one host to another)
- adapt to changing temperature and pH (able to multiply in a refrigerator)
What is the usual environment Listeria live in? Are they commensal? What temperature are they most commonly found at?
- grow as saprophytes in soil and decaying vegetation in the environment (sewage, water, feed, food)
- NO, they are a frank pathogen
- abundant at colder temperatures in the EU and North America (< 4 degrees C)
What is Listeria’s host range like? What are they most common in?
- DIVERSE - humans, mammals, birds, fish, insects
- ruminants, mainly sheep —> seasonal outbreaks
- sporadic in pigs and horses
What 3 body structures contribute to Listeria’s virulence?
- flagella (1-5): motility, adhesion, invasion
- internalin (A, B, C): adhesion, invasion (like a drill)
- invasion-associated protein (iap): adhesion, invasion
What 4 toxins contribute to Listeria’s virulence?
- β-hemolysin - pore-forming lysis on endocytic membrane of the host to free itself from lysosomes and get into the cytoplasm of host cells
- listeriolysin O - same as above
- listeriolysin S - kills competing gut microbiota
- actin-polymerizing protein (actA) - instructs host cell to deposit actin filaments on the end of Listeria that it is able to use to propel into nearby cells (zipper mechanism)
Why does the zipper/actin rocket method work so well for Listeria spread?
allows Listeria to propel from cell to cell without being exposed to antibodies, complement, and phagocytes
What are the 3 major manifestations in neural listeriosis?
- microabscesses in brain
- ataxia, “circling disease”
- unilateral facial paralysis - head tilting to one side, unilateral ear dropping, tongue protrusion, salivation
