lab diagnosis of Escherichia coli

1. Escherichia coli
Lab 4
Prepared by
Samira Fattah
Assis. Lec.
College of health sciences-HMU

2. • commonly found in the lower intestine.
• Most E. coli strains are harmless.
• fecal-oral transmission is the major route through which
pathogenic strains of the bacterium cause disease.

3. General character:
• Rod-shape
• Gram negative
• Facultative anaerobic
• Motile with peritrichous flagella
• Some strains are encapsulated.

4. Laboratory diagnosis:
Specimen:
• Urine.
• pus
• blood
• stool
• CSF
• sputum

5. • Microscope (gram stain):
• Gram negative rode shape bacteria.

6. On blood agar
• E. coli appear as medium sized,
smooth, round, grayish-white
colonies on blood agar.
• Some strains produce beta
hemolysis.

7. On macConkey agar
• the red color of the bacterial growth
indicates E. coli is able to ferment lactose.

8. On EMB
• Ferment lactose.
• blue-black colonies with a greenish metallic sheen.

9. Biochemical test

10. • Oxidase test
• Oxidase –negative
• Catalase test
• positive
Bubble formation

11. Escherichia coli
motile
Motility test
• Escherichia coli is highly
motile and will show
turbidity throughout
the tube.
Klebsiella pneumoniae
Non motile

12. API test:
indole test is +ve
gelatinase -ve
urease test –ve
no H2O production

13. • Serologic test
For serotyping (Epidemiologic information)