Listeria and Rhodococcus Flashcards
(34 cards)
Microscopical examination of Listeria
Gram +
Medium sized rods or coccobacilli
Peritrichous, motile at temp 20-25 degrees C
No flagella at 37 degrees C
Arranged in V form or palisade arrangement
Listeria cultivation properties
S (rarely R) form
Aerobe or facultative anaerobic (grow at 10% CO2)
Grow at 3-35 degrees C (wide range of temp and pH)
24 hours
Listeria reaction to catalase and oxidase
Catalase +, oxidase -
Diagnostic test for Listeria
Hydrolyse aesculine - 10% NaCl
Where can we find Listeria?
Saprophytes, present in:
Soil
Plants
Vegetation
Faeces
Silage (pH over 5,5)
Infections of Listeria may result in (3)
Septicaemia
Encephalitis
Abortion
Name a food-borne pathogen
Listeria monocytogenes.
Found in milk, meat and vegetable, and can multiply at refrigerator temperature!
Name pathogenic species of Listeria
Listeria monocytogenes and Listeria ivanovii
Non-pathogenic species of Listeria
Listeria innocua and Listeria grayi
What does Listeria monocytogenes cause?
Septicaemic listeriosis in young animals
Neural listeriosis (Circling disease) and abortions in sheep, goats and cattle
Iritis in cattle
What does Listeria ivanovii cause?
Abortions in sheep and cattle
Virulence factors of Listeria (5)
Listeriolyzin O - destroy membranes of phagocytic vacuoles
Phospholipase C
Actin-based motility
Exoenzymes and toxins
Stress protein
How does Listeria invade host cells?
Listeria invade both phagocytic and non-phagocytic cells
Survive and replicate intracellularly
Transfer cell-to-cell without exposure to humoral defence mechanisms
Spread via lymph and blood
Have affinity to CNS and placenta
Material for cultivation of Listeria
Cerebrospinal fluid, placenta, fetus, liver, blood, spleen, milk, meat
Listeria on meat-peptone-broth
Homogenous turbidity
Listeria on meat-peptone-agar
S form
Small
Transparent
Listeria on blood agar
S form
Small
Greyish-white colonies
L. monocytogenes have narrow zone of b-hemolysis
L. ivanovii have wide zone of b-hemolysis
CAMP test for Listeria monocytogenes
positive with St. aureus
CAMP test for Listeria ivanovii
positive with rhodococcus equi
CAMP test for Listeria innocua
Negative
Commercial selective and indicator media for Listeria
PALCAM medium. Double-indicator system:
1. Aesculin and iron
2. Mannitol and phenol red
Listeria monocytogenes reaction with aesculin
L. monocytogenes hydrolyses aesculin resulting in black zone around colonies.
Does NOT ferment mannitol - makes it easy to differentiate from contaminants such as mannitol, enterococci and staphylococci.
Medium is changed from red to yellow.
Listeria on:
Catalase
Oxidase
Glucose
Mannitol
Catalase +
Oxidase -
Glucose +
Mannitol -
L. monocytogenes:
rhamnose
xylose
rhamnose +
xylose -
