Question

1- Symptoms – blood work, fever, all major sign and symptoms of Listeria monocytogenes

2- Tests for detection – serological and DNA based (also includes V, B, P, G+/G-)

3- Pathogenesis – virulence factors, toxins spores etc how it damages our bodies

Answer 1

L. monocytogenes usually colonizes the small intestine. The bacterium enters the cells lining the gastrointestinal tract through a mechanism called the “zipper“ mechanism using invasion molecules to disrupt the host’s cell membrane. Macrophages will also phagocytose the bacteria in order to neutralize it in a phagolysosome. A phagolysosome is formed inside phagocytes by first engulfing the bacteria in a vacuole then fusion of this vacuole with a lysosome containing digestive enzymes. Pathogenic strains of L monocytogenes will produce an exotoxin and virulence factors called listeriolysin O, phospholipase A, phospholipase B and phospholipase C in order to destroy the phagolysosome’s membrane and escape. The bacterium will then multiply in the cytoplasm of the host’s cell and uses the cell’s thin filaments called actin as a tail to move towards the membrane. L monocytogenes will then exit from the cell using pseudopods and enters the neighboring cell forming a double membrane vacuole that the pathogen will need to escape from using the same virulence factors. The pathogen will then spread from cell to cell repeating it’s life cycle and hiding from the immune system.