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


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.

Enterobacter aerogenes: Introduction, Identification Features, Keynotes, and Enterobacter aerogenes Footages
Fig. 1. E. aerogenes mucoid pink colony on MacConkey agar, 2. Biochemical tests and, 3. Antibiogram Pattern

Biochemical Reactions of Enterobacter aerogenes

Basic FeaturesProperties
1. Gram StainingGram-Negative Rods (GNRs)
2. SporeNon-Sporing
3. CapsulePositive
4. MotilityPositive
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. Gas Positive
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 fermentationPositive
22. Sucrose fermentationNegative
23. Xylose fermentationPositive
24. Mannitol fermentationPositive
25. Gamma-Glutamyl transferasePositive
26. ONPG (β-galactosidase)Positive
27. Phenylalanine Deaminase (PDA)/PPA TestNegative
28. Tetrathionate reductaseNegative
29. Esculin Hydrolysis testPositive
30. Lysine Decarboxylase TestPositive
31. Ornithine Decarboxylase TestPositive
32. Arginine Dihydrolase TestNegative
Table: Properties of Enterobacter aerogenes

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 aerogenes colony morphology on MacConkey agar
Fig. E. aerogenes colony morphology on MacConkey agar showing mucoid pink colonies

Enterobacter biochemical tests in TSI, MIU and Citrate agar

Enterobacter aerogenes biochemical tests in TSI, MIU and Citrate agar
Fig. E. aerogenes biochemical tests in TSI, MIU, and Citrate agar

E. aerogenes antimicrobial susceptibility testing (AST) pattern Demo

Enterobacter aerogenes antimicrobial susceptibility testing (AST) pattern Demo
Fig. E. aerogenes antimicrobial susceptibility testing (AST) pattern Demo

AST Pattern

AST_Enterobacter aerogenes
Report: AST_Enterobacter aerogenes

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

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