10 – Listeria Flashcards
1
Q
Microbiological characteristics
A
- Biocontainment level 2
- Short gram-positive rods,
- Coccoid
- Facultative anaerobes
o Growth enhanced by CO2 - Small beta-hemolytic colonies on blood agar
- Grow under a wide range of conditions
o 3-4.5 degrees C
o pH 5.6-9.6
2
Q
L. monocytogenes microbial characteristics
A
- Facultative intracellular parasite
- Displays ‘tumbling’ motility in broth
3
Q
Natural host or habitat
A
- Part of normal microbiota
o Intestinal tract
o Found in feces (human and animals)
o Can be recovered from milk of sheep after lambing
o Raw diary and meat products - Decaying plant material (ex. silage, pH range 5.9-9.6)
- Can survive in environment for long periods (reported 2 years in dry soils)
4
Q
Taxonomy
A
- Catalase positive or not to differentiate from Strept. Or Entero.
- If positive
o CAMP R. equi
o CAMP S. aureus
o Hemolysis
5
Q
Virulence factors
A
- Internalin A and B
- Listerolysis O
- Actin-polymerizing protein
- Phospholipase C
6
Q
Internalin A and B
A
- Surface proteins which bind to host cells
- Induces phagocytosis which is first step in invasion
7
Q
Listerolysin O
A
- pH dependent pore forming toxin
- lyses phagosome
- *allows organism to escape into cytoplasm
8
Q
Actin-polymerizing protein
A
- Hijacks cell actin, push organisms into adjacent cells
9
Q
Phospholipase C
A
- Disrupts membranes
- Involved in organism spreading from cell-to-cell
10
Q
L. monocytogenes (ruminants)
A
- Present in feed to be ensiled and grows in decaying plant material
- Target silage pH varies (should be less than pH5)
o Insufficient acidic silage can harbour viable organisms - Ingested along with feed
- *enter body through mouth
11
Q
Compromised barriers allowing L. monocytogenes to enter
A
- Mucosal damage
- Teeth cutting
- Tooth loss
- *often get neural form
12
Q
Neural form of L. monocytogenes
A
- Will migrate via trigeminal nerve into brain
- Acute meningoencephalitis and micro abscesses
o ‘circling’ diseases
o Neurological signs
13
Q
L. monocytogenes (ruminants): ingested or inhaled
A
- Sepsis and abortions
o Predilection for uterus and fetal tissue in ruminants
o Aborted fetuses=biohazardous (especially for pregnant women)
L. monocytogenes: abortion is sporadic - Typically occurs in animals without prior clinical signs
- Fetus born macerated or very weak if alive
- Effect on fertility transient (recovered animals through to be resistant to reinfection)
14
Q
L. monocytoses: control
A
- Antimicrobial prophylaxis with tetracycline has been used
- Remove abort uses
- Test silage
15
Q
L. monocytogenes (chickens)
A
- Sporadic in poultry and waterfowl (young birds most susceptible)
- Septicaemic and encephalitic form
- Perhaps associated with cold, wet conditions
- ID of source is key!
o Can be difficult, found in poultry litter, birds shed in feces
