Listeria

Question 1

Listeria characteristics

Answer 1

-biocontainment level 2
-short gram positive rods (and some coccoid)
-facultative intracellular anaerobes; growth enhanced by CO2
-small beta-hemolytic colonies on blood agar
-grow under wide range of temperatures and pH)
-displays tumbling motility in broth (L. monocytogenes)

Question 2

Listeria habitat

Answer 2

1. part of normal microbiota
   -intestinal tract
   -found in feces
   -can be found in milk of sheep after lambing
   -raw diary and meat products

2.decaying plant material (silage; ph 5.6-9.6)

3.Environment for long periods (2 yrs in dry soil)

Question 3

Listeria Taxonomy

Answer 3

-Catalase differentiates listeria from streptococcus or enterococcus

-Tumbling motility differentiaties Listeria monocytogenes from L. ivanovii

Question 4

Hemolysis differences between Listeria ivanovii and monocytogenes

Answer 4

ivanovii= wide zone

monocytogenes= narrow zone

Question 5

Virulence factors of listeria

Answer 5

1. internalin A and B
2. Listerolysin O
3. Actin-polymerizing protein
4. Phospholipase C

Question 6

Internalin A and B

Answer 6

surface proteins which bind to host cells, induces phagocytosis allowing for invasion

Question 7

Listerolysin O

Answer 7

-pH dependent pore forming toxin, lyses the phagosome, allowing organism to escape into the cytoplasm

Question 8

Actin-polymerizing protein

Answer 8

-hijacks host cell actin and uses them to push organisms into adjacent cells

Question 9

Phospholipase C

Answer 9

Disrupts the membranes allowing organism to spread from cell to cell

Question 10

Listeria monocytogenes effect on ruminants

Answer 10

-common in their environment (feces, plants, fertilizers)… insufficient acidic silage can home microbes. Animals ingest in feed (compromising mucosa, teeth)
-causes encephalitis, abortion

Question 11

How does listeria monocytogenes cause encephalitis?

Answer 11

-microbes enter through the mouth and migrate through trigeminal nerve into the brain

-results in meningoencephalitis, microabscesses which is clinically seen as circling disease and neurological signs

Question 12

Listeria monocytogenes effect on monogastrics, birds, horses

Answer 12

septicemia

Question 13

Listeria monocytogenes effect on humans

Answer 13

-septicemia, abortion, gastroenteritis

Question 14

Listeria ivanovii effect on sheep and cattle

Answer 14

-abortion in ruminants (3-5wks following exposure)
**bacteria is thought to be more specific

Question 15

L ivanovii previous name

Answer 15

Previously called L. monocytogenes serotype 5

**more host specific than L. monocytogenes

Question 16

How are abortions and septicemias occuring?

Answer 16

Listeria ingested or inhaled. L. monocytogens has a particular predilection for uterus and fetal tissues
>placentitis, fetal septicemia, abortions, stillbirths, neonatal deaths

**aborted ruminant fetuses are biohazardous

Question 17

Abortion occurrence

Answer 17

-sporadic, herd/flock incidence ~15% or less

-typically occurs in cattle (last 2 mths of gestation) and sheep (last mth of gestation)

-often recovered animals thought to be resistant to reinfection

Question 18

Management/treatment of L monocytogenes

Answer 18

=antimicrobial prophylaxis with tetracycline
-remove abortuses
-test silage

Question 19

L monocytogenes in poultry

Answer 19

-sporadic; young birds more susceptible

Two forms:
1. Septicemic: emaciation and diarrhea
2. Encephalitic: depression, inccordination, neural signs

-linked with cold, wet conditions. Found in poultry litter and birds shed in feces

Question 20

L. monocytogenes in dogs and cats

Answer 20

-uncommon. Need a very high infectious dose

-typically ingested; disease can be GI or neurological
>fever, diarrhea, vomiting in GI disease
>localization to placenta or CNS in systemic spread

Question 21

L. monocytogenes in humans

Answer 21

-high risk for pregnant women (cause abortion), older adults, and compromised immune systems

Question 22

Listeria syndromes in people

Answer 22

1. Transient carrier in GI tract
2. Acute (often during pregnancy)
   -flu symptoms, mother recovers, fetus survival depends on gestational age)
3. Non-pregnant adults= sepsis, meningoencephalitis, local infections

Question 23

Where do humans acquire listeria?

Answer 23

Mostly from contaminated foods
-uncooked meat and vegetables
-raw dairy products
-processed foods (soft cheese, smoked meat)

**can grow at 4degrees (fridge!)

Regulated and recalled by CFIA

Question 24

Specimens to collect for Listeria

Answer 24

Septicemic form: viscera (liver, kidney, spleen)

CNS form: CSF, brain stem

Abortions: placenta and fetus

Silage: Aseptically collect 100g in sterile container

Question 25

Sample handling for listeria

Answer 25

-Need to culture ASAP
-may freeze at -20 degrees to prevent growth of contaminants

Question 26

Lab ID of listeria

Answer 26

-Culture on blood agar
-Selective media available (CHROMagar)
-cold enrichment may facilitate growth

Question 27

Zoonotic factors of listeria

Answer 27

-Pregnant women should avoid contact with sheep, goats (abortuses at lambing can harbour microbes)
-Vets and abattoir workers
-L. ivanovii can be isolated from severly immunocompromised people

Question 28

Treatment options for listeria

Answer 28

1. Therapy
   -ruminants: high dose penicillin
   -companion animals: ampicillin and gentamicin

**Avoid cephalosporins, and fluroquinolones

2. Control measures
   -remove poor silage from feeding

Question 29

Hypopyon

Answer 29

Accumulation of WBCs in the anterior chamber of the eye

Question 30

Endophthalmitis

Answer 30

inflammation that affects the interior of the eyeball