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Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
Veterinary bacteriology


Species/Subspecies: Neorickettsia risticii
Etymology: Gemus name: the new rickettsia.
Species epithet: named after Miodrag Ristic.
Significance:The disease is common in some regions of the United States, Canada and South America. Has also been detected in France and Italy, but never in Sweden. However, it may occur in horses imported from the United States.
  [Of minor importance]   
Old Species Name(s):Ehrlichia risticii
Taxonomy:
Phylum
Proteobacteria
Class
Alphaproteobacteria
Order
Rickettsiales
Family
Anaplasmataceae 
Genus
Neorickettsia
Type Strain: Illinois = HRC-IL = ATCC VR-98.
Macromorphology (smell): Cannot be cultured on cell free substrates (for instance agar plates)
Micromorphology: Small (0.8 x 1.5 µm) nonmotile coccoid rods
Gram +/Gram -:G-, is normally not gram stained. Lymph node aspirate can be stained by Giemsa or Machiavello-staining, which gives blue and red bacteria, respectively.
Metabolism: Aerobic
Catalase/Oxidase:
Fermentation of carbohydrates: Is not used for identification of Neorickettsia spp. Furthermore, many intracellular bacteria lack enzymes for carbohydrate metabolism because of evolutionary gene reduction.
Spec. Char.:
Vector: Liver fluke (Fasciola gigantica)
Reservoir: Insects infected by the liver fluke
Disease:Potomac horse fever or equine monocytic ehrlichiosis or equine scours.
Hosts: Horse, (cattle, mouse, dog and cat)
Clinical Picture: Acute watery diarrhea. Abortion if the fetus is infected (rare).
Genome Sequence:
Acc-noStrainSize (bp)Genome
CP001431 Illinois 0 879 977  1c + 0 

16S rRNA Seq.:
Acc-noStrainNumber of NTOperon
M21290 (T) 1498 

Taxonomy/phylogeny:
Neorickettsia risticii  
Three species have been described within the genus, which is most closely related to the genera Anaplasma and Ehrlichia.The name Neorickettsia risticii has not been officially aproved because a type strain has not been deposited in two international culture collections.
Comment:Intracellular and infects mononuclear leucocytes
Updated:2015-12-16

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