Enterobacteriaceae: Introduction, Phenotypic Features and Related Videos
The family Enterobacteriaceae is a very large group of gram-negative bacteria that possess a number of common morphological and biochemical properties and similar DNA base compositions. The widely used systems for the classification of Enterobacteriaceae are
Even having certain differences, the general approach is the same. A family is a group of subdivisions or tribes and each tribe consists of one or more genera. Similarly, each genus consists of one or more subgenera and species. The species are classified into types like biotypes, serotypes, bacteriophage types, and colicin types.
The family Enterobacteriaceae has following general phenotypic features-
They are small gram-negative rods.
Having usual cell structure (non sporulated)
Motile by peritrichous flagella.
Grow on ordinary medium.
Grow both aerobically and anaerobically.
Grow without the addition of sodium chloride or other supplements.
Grow well on MacConkey agar.
Ferments D-glucose and other sugar, often with gas production.
Catalase test positive.
Oxidase test negative.
Reduce nitrate to nitrite
Contain the enterobacterial common antigen (ECA) and
They have a 39-59% guanine plus cytosine (G+C) content of DNA.
All the members of the family Enterobacteriaceae are catalase-positive except Shigella dysentery type 1.
All the members of the family Enterobacteriaceae are oxidase negative except Plesiomonas shigelloides which is oxidase test positive.
All oxidase-positive bacteria are catalase test positive except Kingella, Eikenella, and Cardiobacterium those are catalase test negative.
# E. coli the member of Enterobacteriaceae on MacConkey agar, blood agar, and Chocolate agar as shown below-
#E. coli under microscope|| Gram stain ||Gram Negative bacilli or Gram-negative rods as shown below-
# Escherichia coli growth on nutrient agar, MacConkey agar, and Blood agar and also biochemical tests- Triple Sugar Iron(TSI) agar Sulphide Indole Motility (SIM) test Citrate Utilization Test Urea hydrolyzation Test as shown below
# Klebsiella pneumoniae growth on nutrient agar, MacConkey agar, and Blood agar and also biochemical tests- Triple Sugar Iron(TSI) agar Sulphide Indole Motility (SIM) test Citrate Utilization Test Urea hydrolyzation Test as shown below
# Swarming growth of Proteus on blood agar as shown below-
Salmonella Typhi isolated from Blood Culture- Growth of Salmonella Typhi on nutrient agar, MacConkey agar, and blood agar Growth of Salmonella in the blood culture bottle Biochemical tests of Salmonella Typhi in TSI SIM Citrate agar Urea agar
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