Enterobacteriaceae: Introduction and Phenotypic features

E. coli on MacConkey agar enterobacteriaceae

  Enterobacteriaceae

The family Enterobacteriaceae is a very large group of gran negative bacteria that posses a number of common morphological and biochemical properties and similar DNA  base compositions.

The widely used systems for the classification of enterobacteriaceae are

Bergey’s manual

Kauffmann and

Edward -Ewing.

Even having certain differences, the general approach is same.

The  family is  a group of subdivision or tribes and  each tribe consists of one or more genera.Similarly, each genus consists of one or more sub genera and species. The species are classified into types like biotypes, serotypes, bacteriophage types and colicin types.

This family has following tribes

Tribe 1: Escherichiae

Genus 

  1. Escherichia 
  2. Edwardsiella
  3. Citrobacter
  4. Salmonella
  5. Shigella

Tribe 2: Klebsiellae

Genus

  1. Klebsiella
  2. Enterobacter
  3. Hafnia
  4. Serratia

Tribe 3: Proteeae

Genus

  1. Proteus
  2. Morgenella
  3. Providencia

Tribe 4: Erwinieae

Genus

  1. Erwinia

Phenotypic features

The family enterobacteriaceae has following general phenotypic  features-

1. They are small gram negative rod

2. Having usual cell structure (non sporulated)

3. Motile by peritrichous flagella.

4. Grow on ordinary medium.

5. Grow both aerobically and anaerobically.

6. Grow without addition of sodium chloride or other supplements.

7. Grow well on MacConkey agar.

8. Active biochemically.

9. Ferments D-glucose and other sugar, often with gas production.

10. Catalase test positive.

11. Oxidase test negative.

12. Reduce nitrate to nitrite

13. Contain the enterobacterial  common antigen (ECA) and

14. They have a 39-59% guanine plus cytosine (G+C) content of DNA.

 Key Notes:

All the members of family enterobacteriaceae are catalase  positive except Shigella dysentery type 1.

All the members of 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.

Bibliography

1. Topley Wilson ‘s Microbiology of Microbial infectious Bacteriology-2

2. Bailey & Scott’s Diagnostic Microbiology

Thirteen 13 Edition

3. Textbook of Practical Microbiology

Subhash Chandra Parija

This is the short explanation of family Enterobacteriaceae introduction and Phenotypic features.

If any query, ask without hesitation.

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