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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:2021-09-29

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"Dear child has many names" (call it what you will...)

For a long time, Rhodococcus hoagii was refer­red to Rhodo­coccus equi on VetBact, because we experienced some resistance to the name that is now considered to be the correct one, i.e. Rhodococcus hoagii. Now you can find the bacterium in question under the correct name in VetBact, but you can also find the bacterium when searching for the old name. 

Published 2021-10-10. Read more...

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