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Species/Subspecies: Listeria monocytogenes
Etymology: Genus name: named after the British surgeon Lord Lister.
Species epithet: monocyte producing.
Significance:  [Very important]   
Type Strain: ATCC 15313 = NCTC 10357.
Macromorphology (smell):
Listeria monocytogenes Listeria monocytogenes 
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.
Gram +/Gram -:
Fig. 13:3.Gram staining of Listeria monocytogenes, strain SLV365.

Metabolism: Facultatively anaerobic.
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.
Special Media:
Listeria monocytogenes 
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).
Hosts: Ruminants (common in sheep), birds, humans etc.
Disease (Swedish):Listerios. Encephalit, abort, sepsis och ögoninfektion (idisslare). Matförgiftning och abort (människa).
Disease (English):Listeriosis. Encephalitis, abortion, septicemia and eye infections (ruminants). Food poisoining and abortion (humans).
Clinical Picture: Neural form: most common in animals (circling disease). Septicemic form: necrotic foci of the liver and myocardium. Metrogenic form: abortion, stillbirth or diseased offspring.
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:
Acc-noStrainSize (bp)Genome
NC_003210 EGD-e 2 944 528 1c + 0 

16S rRNA Seq.:
Acc-noStrainNumber of NTOperon
X56153 (T) 1469 

 Listeria monocytogenes
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

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Swedish University of Agricultural Sciences