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

Introduction

Enterobacter aerogenes is a Risk Group 2 organism and is responsible for nosocomial infection, human and animal diseases and normally present in the gut of vertebrates and also in the environment and thus it may be the organism of concern for on health scheme. Classification of bacterium is as follows-

• Kingdom: Bacteria
• Phylum: Proteobacteria
• Class: Gammaproteobacteria
• Order: Enterobacteriales
• Family: Enterobacteriaceae
• Genus: Enterobacter
• Species: Enterobacter aerogenes

E. aerogenes is a member of a family, Enterobacteriaceae and it is a Gram-negative, motile, straight rod, a non-spore-forming, and capsulated bacterium. A colony is normally circular, raised, and moist with an entire margin and vary from beige to off-white and it forms a large, mucoid, pink colony like Klebsiella on MacConkey medium. It can cause a variety of clinical conditions in the human-like eye and skin infections, meningitis, bacteremia, pneumonia, and urinary tract infections.

Biochemical Reactions of Enterobacter aerogenes

Basic Features	Properties
1. Gram Staining	Gram-Negative Rods (GNRs)
2. Spore	Non-Sporing
3. Capsule	Positive
4. Motility	Positive
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	Positive
22. Sucrose fermentation	Negative
23. Xylose fermentation	Positive
24. Mannitol fermentation	Positive
25. Gamma-Glutamyl transferase	Positive
26. ONPG (β-galactosidase)	Positive
27. Phenylalanine Deaminase (PDA)/PPA Test	Negative
28. Tetrathionate reductase	Negative
29. Esculin Hydrolysis test	Positive
30. Lysine Decarboxylase Test	Positive
31. Ornithine Decarboxylase Test	Positive
32. Arginine Dihydrolase Test	Negative

Keynotes on Enterobacter

• Enterobacter aerogenes is naturally gut flora of many vertebrates.
• Newly Named Klebsiella aerogenes is previous Enterobacter aerogenes.
• It is named Klebsiella aerogenes due to 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.

E. aerogenes Footages

E. aerogenes colony morphology on MacConkey agar

Enterobacter biochemical tests in TSI, MIU and Citrate agar

E. aerogenes antimicrobial susceptibility testing (AST) pattern Demo

AST Pattern

Further Readings

• https://www.canada.ca/en/environment-climate-change/services/evaluating-existing-substances/screening-assessment-enterobacter-aerogenes.html
• Bergey’s Manual of Systematic Bacteriology [3] : Volume 2: The Proteobacteria , Part B: The Gammaproteobacteria
• 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