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Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
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Species/Subspecies: Citrobacter freundii
Etymology: Genus name: citrate-utilizing rod (bacterium).
Species epithet: named after the bacteriologist A. Freund, who first observed that trimethylene glycol was a product of fermentation.
Significance:  [Bacteria in the normal flora, which can sometimes cause disease]   
Taxonomy:
Phylum
Proteobacteria
Class
Gammaproteobacteria
Order
Enterobacteriales
Family
Enterobacteriaceae 
Genus
Citrobacter
Type Strain: ATCC 8090 = CCUG 418 = NCTC 9750.
Macromorphology (smell):
Citrobacter freundii  Citrobacter freundii  
Medium-sized translucent to opaque colonies (2-4 mm in diameter) with glossy surface.
Micromorphology: Straight rods (1.0 x 2.0-6.0 µm), which usually are motile by means of peritrichous flagella.
Gram +/Gram -:
Citrobacter freundii  
G-
Metabolism: Facultatively anaerobic. Can utilize citrate as the sole carbon source.
Catalase/Oxidase:+/-
Other Enzymes: DNase -, esculinase -, ornithine decarboxylase -, tryptophanase v, urease v.
Biochemical Tests: Citrate (+), methyl red +, Voges-Proskauer -.
Fermentation of carbohydrates:
D-glucoselactosemaltoseL-rhamnosesucrose
+(+)++(+)
L-arabinosecellobioseD-mannitolsalicintrehalose
+v+-+
glycerolinulinraffinoseD-sorbitolstarch
+?v+?
All strains ferment glucose under acid production and about 90% of them also under gas production. Sorbose phosphate +.
Spec. Char.:
Hosts: Is an environmental bacterium, which also can be isolated from many different species.
Disease:Is an opportunistic or secondary pathogen, which may cause wound infections. In humans, C. freundii in rare cases, cause food poisoning.
Clinical Picture:
16S rRNA Seq.:
Acc-noStrainNumber of NTOperon
AJ233408 (T) 1505  

Taxonomy/phylogeny:
Citrobacter freundii  
Thirteen species have been described within genus Citrobacter. Citrobacter freundii belongs to the family Enterobacteriaceae and is closely related to members of the genus Klebsiella. In fact, Citrobacter freundii and members of the genus Klebsiella form a monophyletic cluster (see Fig. 142:4 to the left).
Comment:Some strains can easily be confused with Salmonella spp. in routine diagnostics. Grows in the same way on BG XLD and purple agar.
Updated:2020-05-28

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