Listeria

Question 1

Listeria monocytogenes

Distinguishing features

Answer 1

Small gram positive rods
Beta hemolytic, nonspore-forming rod on blood agar, CAMP positive
Tumbling motility in broth, acting jet motility in cells
Facultative intracellular parasite
Cold growth

Question 2

Reservoir

Answer 2

Widespread: animals (GI and genital tracts), unpasteurized milk products, plants and soil
Cold growth: contaminated food, soft cheese, deli meat, cabbage, hotdogs, fruit, ice cream

Question 3

Transmission

Answer 3

Foodborn or vertical or cross the placenta (so mother can transmitted to her infant)

Question 4

Pathogenesis

Answer 4

• Listeriolysin O
  B-hemolysin
  Facilitates rapid egress from phagosome into cytoplasm thus evading killing when lysosomal contents are dumped into phagosome; “jets” directly (by actin filament formation) from cytoplasm to another cell
• immunocompromised status predisposes to serious infection