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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.
Morphologyย 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 ยตm long and 0.5 ยตm broad.
- Poles of the cells are blunt.
- They are non-sporing.
- They are non-capsulated.
- At, 35-37ยฐC, they are non-motile.
- At 25ยฐC, they are motile and exhibit a tumbling motility.
- They possess polar flagella (peritrichous) at 25ยฐC.
- Thirteen serotypes are found.
Genomeย 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%
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