Listeria Monocytogenes

Question 1

Listeria Monocytogenes classification of bacteria

Answer 1

Faculative intracelluar Aerobic
Gram positive ROD

Question 2

properties of Listeria Monocytogenes:
1. How is L. momocytogenes arranged ?

Answer 2

1. V or L shaped formations
2. exhibits tumbling movement

Question 3

Describe the colonies of L. Monocytogenes in blood agar

Answer 3

produce a narrow zone of B- hemolysis; resembles the hemolysis os some streptococci

Question 4

Temperature in which Listeria Monocytogenes grow

Answer 4

Listeria grow in cold temperatures

storage of contaminated food in the refrigertator increase risks of gastroenteritis

“cold enhancement”

Question 5

Pathogenesis of Listeria Monocytogenes:

1. what are the two clinical settings in which listeria Monocytogenes occur ?
2. Sources of the bacteria can be from ?

Answer 5

1. in fetus or newborn, pregnant women
2. unpasteurized milk
   uncooked deli meats
   raw vegetables

note: pregnant women have reduced cell-mediated immunity during the third trimester

Question 6

How is listeria monocytogenes distrubuted

Answer 6

Reservoirs are:
animals
plant
soil

Question 7

How does the bacteria L.Monocytogenes invade cells

Answer 7

Invasion of cells is mediated by internalin made by Listeria and E-cadherin on the surface of human cells

The ability of listeria to invade cells depends on E-caherin and internalin

Question 8

What drug/medication ABX should treat Listeria Monocytogenes ?

Answer 8

Trimethorphim-Sulphamethoxazole

combinations: ampicillin and gentamycin
Listeria gastroenteritis doesnt require treatment

Question 9

what is lysteriolysin ?

Answer 9

produced by listeria monocytogenes which allows the escape from phagosome

Question 10

How can Listeria Monocytogenes move from cell to cell?

Important buzz word for this bacteria

Answer 10

important trait called
“rocket tails”

Actin rockets: filaments that propel bacteria from one human cell to another.

Question 11

Laboratory Diagnosis:

1. how do we test for L. monocytogenes
2. Describe appearance of L. monocyt on blood agar if positive

Answer 11

1. Gram stain and culture
   appearance shape of rods **ressembling diptheroids **
2. Shows formation of small colonies with the **presence of narrow zone of B-hemolysis **

Question 12

Listeria Monocytogenes
compared to Corynebacteria, what is the difference ?

Answer 12

Listeria monocytogenes is motile. Corynebacteria is nonmotile

Question 13

How to confirm the identification of Listeria monocytogenes ?

Answer 13

is made by sugar fermentation tests
and remeber it has rocket tails meaning motiile !!