Enterobacter cloacae: Introduction, Identification Features, Keynotes, and Enterobacter Footages

Introduction of Enterobacter cloacae

Enterobacter cloacae is a facultative anaerobic Gram-negative bacterium of size 0.3-0.6 x 0.8-2.0 μm. It is lacking capsule and spore and it is motile due to flagella which is a member of the Enterobacteriaceae family. E. cloacae is the normal gut flora of many humans. It is one of the common nosocomial pathogens capable of causing a wide variety of infections, like pneumonia, urinary tract infections (UTIs), and septicemia. Most of Enterobacter species are common carbapenem-resistant(meropenem, imipenem, and ertapenem).

Biochemical Reactions of Enterobacter cloacae

Basic FeaturesProperties
1. Gram StainingGram-Negative Rods (GNRs)
2. SporeNon-Sporing
3. CapsuleNegative
4. MotilityMotile
5. PigmentNegative
6. Growth in potassium cyanide (KCN) mediumPositive
7. Catalase testPositive
8. Oxidase testNegative
9. Nitrate reduction testPositive
10. MR (Methyl Red) testNegative
11. VP (Voges- Proskauer) assayPositive
12. OF (Oxidative-Fermentative) testFermentative
13. GasPositive
14. H2S productionNegative
15. Indole formationNegative
16. Urease/ urea hydrolysis testNegative
17. Citrate/ citrate utilizationPositive 
18. DNase testNegative
19. Glucose fermentationPositive 
20. Maltose fermentationPositive 
21. Lactose fermentationNegative
22. Sucrose fermentationPositive
23. Xylose fermentationPositive
24. Mannitol fermentationPositive
25. Acetate UtilizationPositive
26. ONPG (β-galactosidase)Positive
27. Phenylalanine Deaminase (PDA)/PPA TestNegative
28. Lipase testNegative
29. Esculin Hydrolysis testVariable
30. Lysine Decarboxylase TestNegative
31. Ornithine Decarboxylase TestPositive
32. Arginine Dihydrolase TestPositive
Table: Properties of Enterobacter cloacaeenes

Keynotes on Enterobacter

  • Enterobacter aerogenes is the natural gut flora of many vertebrates.
  • Newly Named Klebsiella aerogenes is the previous Enterobacter aerogenes.
  • It is named Klebsiella aerogenes due to the following features- based on numerical taxonomy (Bascom et al. 1971) and phylogenetic analyses of Enterobacteriaceae based on 16S ribosomal RNA (rRNA) gene sequences and gyrB sequence alignments, MALDI-TOF Biotyper analysis and in silico DNA-DNA hybridization which proved a higher similarity between Enterobacter aerogenes and members of the genus Klebsiella than between Enterobacter aerogenes and other members of the genus Enterobacter.
  • Multidrug-Resistant Enterobacter cloacae Complex (ECC) are emerging as a Global expanding threat.
  • 6 species have been assigned to the Enterobacter cloacae complex so far and they are E. asburiae, E. cloacae, E hormaechei, E. kobei, E. ludwigii, and E. nimipressuralis.
  • The nomenclature of the E. cloacae complex is given on the basis of whole genome DNA-DNA hybridizations and phenotypic features.

Enterobacter Footage

The encapsulated strain of Enterobacter aerogenes on MacConkey medium

Encapsulated strain of Enterobacter aerogenes on MacConkey medium
Fig. Encapsulated strain of Enterobacter aerogenes on MacConkey medium

Further Reading

  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2515634/
  • https://www.frontiersin.org/articles/10.3389/fmicb.2019.00044/full
  • Bergey’s Manual of Systematic Bacteriology [3]: Volume 2: The Proteobacteria, Part B: The Gammaproteobacteria
  • https://www.sciencedirect.com/topics/medicine-and-dentistry/enterobacter-cloacae
  • https://pubmed.ncbi.nlm.nih.gov/22827309/
  • https://www.sciencedirect.com/topics/medicine-and-dentistry/enterobacter-aerogenes
  • https://microbewiki.kenyon.edu/index.php/Enterobacter_aerogenes
  • https://eol.org/pages/972692/details
  • https://www.ncbi.nlm.nih.gov/books/NBK8035/
  • https://www.msdsonline.com/resources/sds-resources/free-safety-data-sheet-index/enterobacter-spp/https://catalog.hardydiagnostics.com/cp_prod/Content/hugo/Enterobacter.htm
  • https://pubmed.ncbi.nlm.nih.gov/32493786/
  • http://legacy.bd.com/ds/technicalCenter/inserts/L007471(06)(0506).pdf
  • https://www.sciencedirect.com/science/article/pii/S2352771419300382

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