Family Enterobacteriaceae

Members of the Enterobacteriaceae of veterinary importance:

Genus Species sub-species Serotype
Escherichia Escherichia coli
Escherichia fergussonii
Escherichia hermannii
Escherichia vulneris
Escherichia alberti
Salmonella Salmonella enterica enterica Typhimurium
Dublin
Pullorum
Gallinarum
Enteritidis
 -?  -? -? Choleraesuis
Yersinia
Proteus
Enterobactor
Klebsiella
Shigella
Serratia
Morganella

 

Family properties:

  • Gram – negative rods up to 3 μ m in length,oxidase – negative, have peritrichous flagella
  • non – sporing
  • Grow well on MacConkey agar because they are not inhibited by the bile salts in the medium
  • Mostly strains are opportunistic pathogens, occasionally causing clinical disease in locations other than the alimentary tract.
  • Usual habitat- Intestinal tract
  • Enterobacteria can be arbitrarily grouped into three categories: major pathogens, opportunistic pathogens and non – pathogens
  • The major animal pathogens E. coli, Salmonella species and Yersinia species can cause both enteric and systemic disease. 
  •  Opportunistic pathogens: –  Proteus species, Enterobacter species, Klebsiella species Some other members of the Enterobacteriaceae.
  • Klebsiella is the only NON_MOTILE under this family
  • Lactose fermenters form a pink colony due to acid production from Lactose.
  • Non-lactose fermenters have pale colonies and are alkaline due to utilisation of peptone.
  • Differentiation of Salmonella and E. coli in growth media:

Salmonella: Brilliant green (BG) agar and xylose – lysine deoxycholate (XLD) agar, are used to differentiate Salmonella from other enteropathogens. 

  • On BGA , Salmonella colonies and the surrounding medium show a red alkaline reaction. 
  • On XLD medium the colonies of most Salmonella serotypes are red (alkaline reaction) with black centers due to hydrogen sulfide (H2S) production.