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 Features	Properties
1. Gram Staining	Gram-Negative Rods (GNRs)
2. Spore	Non-Sporing
3. Capsule	Negative
4. Motility	Motile
5. Pigment	Negative
6. Growth in potassium cyanide (KCN) medium	Positive
7. Catalase test	Positive
8. Oxidase test	Negative
9. Nitrate reduction test	Positive
10. MR (Methyl Red) test	Negative
11. VP (Voges- Proskauer) assay	Positive
12. OF (Oxidative-Fermentative) test	Fermentative
13. Gas	Positive
14. H2S production	Negative
15. Indole formation	Negative
16. Urease/ urea hydrolysis test	Negative
17. Citrate/ citrate utilization	Positive
18. DNase test	Negative
19. Glucose fermentation	Positive
20. Maltose fermentation	Positive
21. Lactose fermentation	Negative
22. Sucrose fermentation	Positive
23. Xylose fermentation	Positive
24. Mannitol fermentation	Positive
25. Acetate Utilization	Positive
26. ONPG (β-galactosidase)	Positive
27. Phenylalanine Deaminase (PDA)/PPA Test	Negative
28. Lipase test	Negative
29. Esculin Hydrolysis test	Variable
30. Lysine Decarboxylase Test	Negative
31. Ornithine Decarboxylase Test	Positive
32. Arginine Dihydrolase Test	Positive

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

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