Biochemical reactions of E. coli in TSI, SIM, urea and citrate agar
Table of Contents
Escherichia coli is a member of the family, Enterobacteriaceae and it is a Gram-negative, aerobe, and facultative anaerobic, rod-shaped bacterium. The optimal temperature for growth is 36-37°C with most strains growing over the range 18-44 °C. It is a commensal that is found inhabiting the lower intestine of our body. A small proportion of E. coli strains are pathogenic.
The harmless strains produce vitamin K and prevent the colonization of the intestine by pathogenic bacteria. It is classified into serotypes based on cell wall (O), capsular (K), fimbria (F), and flagellar (H) antigens. e.g. E. coli O157:H7
| Basic Features | Properties |
| 1. Gram Staining | Gram-Negative Rods (GNRs) |
| 2. Spore | Non-Sporing |
| 3. Capsule | Capsulated (many isolates) |
| 4. Motility | Motile |
| 5. Pigment | Negative |
| 6. Growth in potassium cyanide (KCN) medium | Negative |
| 7. Catalase test | Positive |
| 8. Oxidase test | Negative |
| 9. Nitrate reduction test | Positive |
| 10. MR (Methyl Red) test | Positive |
| 11. VP (Voges- Proskauer) assay | Negative |
| 12. OF (Oxidative-Fermentative) test | Fermentative |
| 13. Gas from Glucose | Positive |
| 14. H2S production | Negative |
| 15. Indole formation | Positive |
| 16. Urease/ urea hydrolysis test | Negative |
| 17. Citrate/ citrate utilization | Negative |
| 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 | Variable |
| 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 | Positive |
| 31. Ornithine Decarboxylase Test | Variable |
| 32. Arginine Dihydrolase Test | Negative |
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