This document provides information about Escherichia coli (E. coli): - E. coli is commonly found in the lower intestine of humans and animals and is usually harmless, though some pathogenic strains can be transmitted via feces and cause disease. - It has a rod shape, is gram-negative, facultatively anaerobic, and motile with flagella. Laboratory diagnosis involves examining samples under a microscope, culturing on blood and MacConkey agar to observe colony morphology and color, and conducting biochemical tests like catalase, oxidase, and API tests. Serotyping may also be done for epidemiological purposes.

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)