| Species/Subspecies: | Listeria monocytogenes | |||||||||
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| Categories: | Zoonotic; causes hemolysis; motile; notifiable diseases and bacteria | |||||||||
| Etymology: | Genus name: named after the British surgeon Lord Lister. Species epithet: monocyte producing. | |||||||||
| Significance: | [Very important] | |||||||||
| Taxonomy: | Class Bacilli Order Bacillales Family Listeriaceae Genus Listeria |
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| Type Strain: | ATCC 15313 = NCTC 10357. | |||||||||
| Macromorphology (smell):
| 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+ | |||||||||
| Metabolism: | Facultatively anaerobic. | |||||||||
| Catalase/Oxidase: | +/- | |||||||||
| Other Enzymes: | Esculinase +, lecithinase +, β-D-glucosidase +, hippuricase +, tryptophanase -, urease -. | |||||||||
| Biochemical Tests: | Methyl red +, Voges-Proskauer +. | |||||||||
| Fermentation of carbohydrates: | D-glucose + lactose + maltose ? L-rhamnose + sucrose - L-arabinose - cellobiose ? D-mannitol - salicin ? trehalose + glycerol + inulin ? raffinose ? D-sorbitol v starch - |
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| Spec. Char.: | Psychrotrophic. Can grow at 0-42°C and has temperature optimum at 30°C. Can survive at high NaCl concentrations. | |||||||||
| Special Media:
| 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).
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| 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. | |||||||||
| Genome Sequence: |
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| 16S rRNA Seq.: |
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| Taxonomy/phylogeny:
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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 | |||||||||
| Updated: | 2023-03-08 |