Habitat of Listeria monocytogenes
- They are the natural pathogens of wide range of animals, birds, fish, ticks and crustacean.
- They are saprophytic in soil, water, sewage and plants decaying.
- They occasionally colonizes the human gastrointestinal tract (1-10%).
- They can be isolated from foods for human consumption, including raw and processed meat, dairy products, vegetables and sea fruit products.
- Listeria monocytogenes can cause mastitis in cows, from which large number of bacteria can be shed in the milk.
- They are resistance to the effects of freezing, drying, high heat, high salt and high pH.
- They can also form biofilms.
Morphology of Listeria monocytogenes
- They are gram +ve short rod shaped bacteria.
- They appear cocco-bacillary in clinical materials.
- They are small and slender.
- They are 1-3 µm long and 0.5 µm broad.
- Poles of the cells are blunt.
- They are non-sporing.
- They are non-capsulated.
- At, 35-37°C, they are non-motile.
- At 25°C, they are motile and exhibit a tumbling motility.
- They possess polar flagella (peritrichous) at 25°C.
- Thirteen serotypes are found.
Genome of Listeria monocytogenes
- Singular circular chromosome.
- EGD-e strain is 2,994, 528 base pair long.
- They have 2853 open reading frame.
- 331 genes encodes transport protein.
- GC Content: 39%