|Categories:||Zoonotic; causes hemolysis; motile; notifiable diseases and bacteria|
|Etymology:||Genus name: named after the British surgeon Lord Lister. |
Species epithet: monocyte producing.
|Type Strain:||ATCC 15313 = NCTC 10357.|
||Small (0,5- 1 mm in diameter) colonies, which can be crateriform on certain selective media. Produces a zone of hemolysis on blood agar.|
|Micromorphology:||Long thin rods (0.4-0.5 x 0.5-2 µm) in short chains. Motile by means of a few peritrichous flagella. L. monocytogenes also exhibits actin-based motility (see references 154 and 155 below).|
|Gram +/Gram -:||G+|
|Other Enzymes:||Esculinase +, lecithinase +, β-D-glucosidase +, hippuricase +, tryptophanase -, urease -.|
|Biochemical Tests:||Methyl red +, Voges-Proskauer +.|
|Fermentation of carbohydrates:||
Other carbohydrates: Galactose v, ribose -, xylitol +, xylose -.
|Spec. Char.:||Psychrotrophic. Can grow at 0-42°C and has temperature optimum at 30°C. Can survive at high NaCl concentrations.|
||Colonies of Listeria sp. are blue-greenish on Brillians-Listeria-agar medium because they produce a β-glucosidase. There is also a precipitate around colonies of L. monocytogenes and pathogenic strains of L. ivanovii because they have a lecithinase (see the legend to the figure).|
|Disease:||Listeriosis. Encephalitis, abortion, septicemia and eye infections (ruminants). Food poisoining and abortion (humans).
|Virulence Factors:||The membrane protein internalin, which induces cellular uptake of bacteria by phagocytosis. Listeriolysin O (a hemolysin), which makes it possible for the bacteria to escape from the phagosome before it fuses with a lysosome. The bacteria can polymerise actin by means of the protein Act A, which contributes to their intracellular mobility.|
|16S rRNA Seq.:|
||There are 21 species and subspecies described within the genus and all are very similar. L. monocytogenes and the nonpatogenic L. innocua have almost identical 16S rRNA sequences.|
|Legislation:||Listeriosis is zoonotic and a notifiable disease in Sweden. L. monocytogenes is classified as a potential biological weapon with the NIAID priority code B.|
|Comment:||Can invade cells and is facultatively intracellular (in monocytes).|
|Reference(s):||No. 31, 65, 154, 155|