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
16
Q
L. monocytogenes (chickens): septicaemic form
A
- emaciation
- diarrhea
17
Q
L. monocytogenes(chickens): encephalitic form
A
- depression
-incoordination
-nervous signs
18
Q
L. monocytogenes (dogs and cats)
A
- Uncommon (high infectious dose required)
- Similar pathogenesis as people
o Ingested by eating contaminated food
o Disease can be GI or neurological/systemic - GI disease characterized by fever, diarrhea, and vomiting
19
Q
L. monocytogenes (humans): people at risk
A
- Pregnant women: 10x more likely to be infected (abortion)
- Older adults: 4x
- Compromised immune systems
o Cancer, HIV/AIDS
o Less obvious: liver or kidney disease
20
Q
Syndromes associated with Listeria in people
A
- Transient carriage in GIT
- Acute symptomatic illness
o During pregnancy, flu like symptoms, mother recovers and maybe fetal depending on gestational age - Newborns can be very severely ill
- Non-pregnant adults
o Sepsis, meningoencephalitis
o Focal infection (abscesses) at variety of sites
21
Q
L. monocytogenes most often acquired from contaminated food
A
- uncooked meats and veggies
- raw dairy products
- processed foods
*grows at 4 degree C in the fridge
*CFIA recalls all food products contaminated with it
22
Q
Unusual presentation of Listeria in person
A
- Did not have encephalitis
- Only affected with endophthalmitis
- *hypopyon is not uncommon in large animals with encephalitis
23
Q
Hypopyon
A
- Accumulation of WBCs in the anterior chamber of eye
- Purulent material in eye may=infection in brain
24
Q
Endophthalmitis
A
- Inflammation that affects the interior of the eyeball
25
Q
L. ivanovii
A
- previously know has L. monocytogenes serotype 5
- cause of abortion in ruminants (3-5 weeks following exposure to spoiled feeds)
- outbreaks of abortion reported in sheep
-mores host SPECIFIC
26
Q
Species to collect
A
- Septicaemic form: viscera (liver, kidney, spleen)
- CNS form: CSF, brain stem
- Abortions: placenta, fetus
- Silage: aseptically collect 100g in sterile container
27
Q
Sample handling
A
- Culture ASAP
- May freeze at -20 degree C to prevent growth of contaminants
28
Q
Lab ID
A
- Grown using traditional culture methods (ex. blood agar)
- Selective media readily available
- Cold-enrichment may facilitate growth
29
Q
Zoontic/interspecies transmission
A
- Pregnant women should avoid contact with sheep and goats particularly during lambing and kidding
- Vets and abattoir workers
- L. ivanovii may be isolated from severly immunocompromised people
30
Q
Treatment options
A
- Therapy
- Drugs
- Control measures
31
Q
Therapy
A
- Ruminants: high dose penicillin
- Companion animals: ampicillin + gentamicin
32
Q
Drugs to avoid/intrinsic resistance
A
- Cephalosporins
- Fluoroquinolones
33
Q
Control measures
A
- Removing poor quality silage from feeding
