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Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
Veterinary bacteriology


Species/Subspecies: Listeria monocytogenes
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:
Phylum
Firmicutes
Class
Bacilli
Order
Bacillales
Family
Listeriaceae 
Genus
Listeria
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-glucoselactosemaltoseL-rhamnosesucrose
++?+-
L-arabinosecellobioseD-mannitolsalicintrehalose
-?-?+
glycerolinulinraffinoseD-sorbitolstarch
+??v-
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).
Disease:Listeriosis. Encephalitis, abortion, septicemia and eye infections (ruminants). Food poisoining and abortion (humans).
Hosts: Ruminants (common0 in sheep), birds, humans etc.
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 

Taxonomy/phylogeny:
 
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:2020-10-28

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